FEEDING ECOLOGY AND COMPETITION FOR IN TWO PHILIPPINE (BUCEROTIDAE; Aceros waldeni, Penelopides panini) IN THE BREEDING SEASON

Dissertation to obtain the degree Doctor of Philosophy (PhD) At the Faculty of Biology and Biotechnology International Graduate School of Biosciences Ruhr-University Bochum

Conservation Biology Unit

Submitted by

Basharat Ahmad

From Muzaffarabad, Pakistan

Bochum (January 2013)

NAHRUNGSÖKOLOGIE UND NAHRUNGSKONKURRENZ ZWEIER PHILIPPINISCHER NASHORNVOGELARTEN (Bucerotidae; Aceros waldeni, Penelopides panini) IN DER BRUTZEIT

Dissertation zur Erlangung des Grades eines Doktors der Philosophie (PhD) an der Fakultät für Biologie und Biotechnologie Internationalen Graduiertenschule für Biowissenschaften der Ruhr-Universität Bochum

Conservation Biology Unit

Vorgelegt von

Basharat Ahmad

aus Muzaffarabad, Pakistan

Bochum (Januar 2013)

Supervisor: Prof. Dr. Eberhard Curio Conservation Biology Unit Faculty of Biology and Biotechnology

Co-Supervisor: Prof. Dr. Ralph Tollrian Department of Ecology, Evolution and Biodiversity Faculty of Biology and Biotechnology

Table of contents

Table of Contents

Abstract ...... i Kurzfassung ...... iv Chapter 1 INTRODUCTION ...... 1 1.1 General distribution ...... 2 1.2 Feeding behaviour ...... 3 1.3 Reproduction and sexual behaviour ...... 5 1.4 Nesting Habit ...... 8 1.5 Scope of the present study ...... 10 Chapter 2 MATERIALS AND METHODS ...... 13 2.1 Study area ...... 13 2.2 Methods ...... 15 2.2.1 Field survey and species identification ...... 15 2.2.2 Nest site selection and nest tree characteristics ...... 16 2.2.3 Nest orientation ...... 17 2.2.4 Estimation of population size and breeding pair density ...... 17 2.2.5 Dispersion pattern ...... 18 2.2.6 Feeding ecology...... 20 2.3.7 Statistical analysis...... 21 Chapter 3 RESULTS ...... 22 3.1 Status and characteristics of nest hole trees ...... 22 3.1.1 Status of nest hole trees...... 24 3.1.1.1 Status of nest hole trees of the Dulungan ...... 26 3.1.1.2 Status of nest hole trees of the Tarictic ...... 26 3.1.2 Characteristics of nest hole trees ...... 27 3.1.2.1 Measurements of nest trees of Dulungan ...... 30 3.1.2.2 Measurements of nest trees of Tarictic...... 31 3.1.3 Orientation of the entrance of the nest hole ...... 32 3.1.3.1 Orientation of the entrance of the Dulungan nest holes ...... 32 3.1.3.2 Orientation of the entrance of the Tarictic nest holes ...... 33 3.2 Dispersion pattern ...... 34 3.2.1 Dispersion pattern of the Dulungan ...... 34 3.2.2 Dispersion pattern of the Tarictic ...... 35 3.3 Population density ...... 37 3.3.1 Population dependence on elevation ...... 38 Table of contents

3.3.1.1 Population dependence of the Dulungan ...... 38 3.3.1.2 Population dependence of the Tarictic ...... 40 3.4 Food and feeding ecology ...... 45 3.4.1 Fruit species consumed during the breeding seasons 2009-10 ...... 45 3.4.2 Feeding ecology of the Dulungan ...... 49 3.4.2.1 Food type and food diversity ...... 49 3.4.2.2 Intraspecific nearest neighbour food overlap...... 54 3.4.3 Feeding ecology of the Tarictic ...... 56 3.4.3.1 Food type and food diversity ...... 56 3.4.3.2 Intraspecific nearest neighbour food overlap...... 57 3.4.4 Interspecific nearest neighbour food overlap ...... 58 3.5 Breeding biology ...... 60 3.5.1 Breeding biology of the Dulungan ...... 60 3.5.2 Breeding biology of the Tarictic...... 62 3.5.3 Moulting of feathers of the breeding female ...... 63 3.5.4 Behavioural observations during the breeding season ...... 64 3.5.4.1 Vigilance and nest concealment behaviour of ...... 64 3.5.4.2 Acclimation of hornbills to change of habitat ...... 65 3.5.4.3 Food withholding and fledging ...... 67 3.6 Habitat disturbance and threats to hornbill species ...... 69 Chapter 4 DISCUSSION ...... 73 4.1 Status and characteristics of nest hole trees ...... 73 4.1.1 Status of nest hole trees...... 73 4.1.2 Nest site characters ...... 74 4.1.2.1 Nest height and GBH ...... 75 4.1.2.2 Nest orientation ...... 76 4.1.3 Nest competition ...... 77 4.2 Dispersion pattern ...... 78 4.3 Population density ...... 78 4.4 Food and feeding ecology ...... 80 4.4.1 Fruit species consumed ...... 80 4.4.2 Interspecific competition...... 81 4.4.3 Nearest neighbour food overlap ...... 83 4.4.3.1 Intraspecific nearest neighbour food overlap...... 83 4.4.3.2 Interspecific nearest neighbour food overlap ...... 84 4.5 Breeding biology of the Dulungan and the Tarictic ...... 85 Table of contents

4.5.1 Timing of breeding ...... 85 4.5.2 Clutch size, brood size and fledging ...... 87 4.5.3 Moulting of feathers of the breeding female ...... 88 4.5.4 Behavioural observations during the breeding season ...... 88 Chapter 5 CONCLUSIONS AND RECOMMENDATIONS ...... 90 Chapter 6 REFERENCES ...... 93 Chapter 7 APPENDICES ...... 101 Acknowledgements ...... 119 Erklärung ...... 120 Curriculum Vitae ...... 121 Abstract

Abstract

A study on various ecological aspects with main focus on the feeding ecology and competition for food in two Philippine hornbill species, the Dulungan (= Writhed-billed Hornbill) (Aceros waldeni) and the Tarictic Hornbill (Penelopides panini) during their breeding seasons was conducted in the Central Panay Mountain Range (CPMR), Philippines. The forest, dominated by tree species of the family Dipterocarpaceae, Euphorbiaceae, Moraceae, Myristicaceae, , Sterculiaceae, Rubiaceae, Burseraceae and Acanthaceae, may start from as low as 90m asl (above sea level) and reach as high as about 1,900m. The core research sites cover an area of about 19km2, between 11o 30.96′-11o 39.45′N and 122o 07.04′-122o 09.30′E, from 100m to 800m asl. Field surveys were conducted and the nest holes undergoing cleaning or sealing by the two species, were searched out and put under surveillance for further identification at the species level. Data on various nest site characteristics and evidence for habitat degradation and factors affecting hornbill populations were noted. Statistical tests used included Spearman correlation, regression analysis, Kruskal-Wallis test followed by multiple comparison, Clark and Evans test, Rayleigh test, Watson-Williams’ F-test, Sörensen’s index of community similarity, Horn’s index of overlap and Shannon-Wiener index. A total of 157 nest hole trees were explored within the area of 19km2 of the CPMR. Both hornbills used 43 nest tree species, belonging to at least 18 families. Dulungan and Tarictic used 27 and 25 tree species, respectively with 35% overlap in nest tree species. Most of the nest trees occupied by the Dulungan belonged to Libtog, Balakbakan (Shorea sp.) and Taba-aw (Aglaia sp.). The nest hole trees occupied by the Tarictic belonged to Libtog, Maganhop, Bagilomboy (Syzygium bordenii), Malabuyo (Alangium meyeri), Salong (Canarium asperum) and Toog (Bischofia javanica). 85% of Dulungan nests and 94% of Tarictic nests were found in the main stem. Both species show fidelity with nest holes. Dulungan and Tarictic re-occupied up to 73% and 87% of the nest holes, respectively. Nest height above ground increased with elevation above sea level. There was a positive correlation between nest height above ground and GBH (girth at breast height) of nest trees. The nest hole height above ground was randomly, and the GBH uniformly distributed between 100-700m asl. The Dulungan nest holes were higher above ground than were the Tarictic nest holes. The median height above ground of nest holes used by the Dulungan and the Tarictic was 11m, ranging from 4m to 20m and about 7m ranging from 1m to 18m, respectively. There was a highly significant difference in median nest hole heights above ground used by the two species. Like nest height, Dulungan also used bigger trees with larger girth. The Dulungan and Tarictic, respectively, used the trees with a median GBH of 224cm (ranging from 120cm to 665cm) and 195cm (ranging from 96cm to 323cm). This difference was significant. There was no difference between years in mean orientation of nest holes used by the Dulungan (113o (subtended from north) in 2009 and 105o in 2010) and the Tarictic (113o in 2009 and 24o in 2010). The nest hole entrances used by both species during both breeding seasons were evenly distributed in all directions. Unlike the 2009 breeding season, the mean orientation of nest hole entrances of Dulungan and Tarictic hornbills differed significantly during the 2010 breeding season.

i

Abstract

The value (R=0.839 in 2009 and R=0.752 in 2010) of the Clark and Evans test during the both breeding seasons indicates a significant deviation from randomness in the direction of aggregation of dispersion for the Dulungans. In contrast, Tarictics showed a tendency in the direction of regular dispersion (R=1.268 in 2009 and R=1.086 in 2010) that is an indication of greater territoriality. The total suitable nest tree density available to both species was calculated to be 8.27/km2. The density of suitable nest hole trees available to both hornbills during the breeding seasons 2009 and 2010 was 6.67/km2 and 9.7/km2 respectively. The Dulungan and the Tarictic breeding pair density was calculated to be 4.47/km2 and 5.83/km2 respectively, and the population of 1787 breeding pairs of the Dulungan and 2333 breeding pairs of the Tarictic was estimated in the whole CPMR. The Dulungan was recorded between 280m and 800m asl, and the Tarictic between 100m and 610m asl; however, most of the Dulungan and the Tarictic breeding populations were confined to areas between 450-600m asl and 400-550m asl, respectively. There was no evidence of a difference in number of breeding pairs of the two species while controlling for elevation above sea level. The average number of fruit species collected from nest holes of both species during the two breeding seasons was 6.2 species. The maximum number of fruit species collected from the nest holes was 17 for Dulungan, and 13 for Tarictic breeding pairs. The fruit species belonged to about 24 families, 31 genera and 52 species. The most common species belonged to families Myristicaceae, Myrtaceae, Palmae, Moraceae and Meliaceae. Together, both hornbills utilized 52 fruit species, the Dulungan 51 species and the Tarictic 38 fruit species, with an overall diet overlap of (Sörensen-Index) Is=83 percent. Both hornbills being syntopic and using the same fruit resources, and a high diet overlap indicate that both species might get in strong competition for the same fruit species during the period of shortage of these fruits. An overall mean nearest neighbour distance and mean percent food overlap for both species together were 157m and 39%, respectively, and there was a highly significant negative correlation between the two parameters. The fruit species delivered frequently by the Dulungan during the two breeding seasons were Uya-oy (Planchonia spectabilis) followed by Pili (Canarium sp.) and Maguhansol (Sandoricum koetjape). Among fruit families, Meliaceae, Myristicaceae, and Lecythidaceae were frequently consumed by the Dulungan. Fruit species consumed frequently by the Tarictic were Pili (Canarium sp.), Uya-oy (Planchonia spectabilis) and Bugohansol (Prunus fragrans). The most preferred fruit families consumed by the Tarictic during both seasons were Sapotaceae, Myristicaceae and Burseraceae. The Shannon-Wiener diversity index shows that the Dulungan is more of a generalist with regard to fruit consumption than the Tarictic. The Dulungan depends almost solely on fruits during the breeding season while the Tarictic supplements its diet with animal food as well.

Intraspecific food overlap (Is) for nearest neighbour breeding pairs of the Dulungan and the Tarictic ranged from 0-100% and 22-100% respectively. No or low overlap in the diet of broods of the same species might be an indication of fruit shortage and partitioning of resources to mitigate effects of intraspecific competition. Tarictic broods during fledging showed that the diet was composed of 97.5% of fruits and 2.5% of animal food. The Tarictic male, in a run, delivered fruits of a single species or sometimes complemented it with animal food that consisted of lizards, grasshoppers, beetles, flies, and other . The mean number of visits and mean number of food items per day was 9.8 and 189, respectively. The mean number of food items per visit was recorded as 19.4. 66.7% of feeding visits contained only fruits and 18% contained both fruits and animal food, while during 15% only animal food was delivered. ii

Abstract

In contrast to intraspecific food overlap, interspecific food overlap between Tarictic and Dulungan did not exceed 66%, and the correlation between the nearest neighbour distance between both species and food overlap was also weak. This might indicate a shift in food selection to avoid competition for food between two species. The timing of breeding might vary in different areas, and different years. Dulungan started breeding usually in early March and fledging in late June and early July. Breeding commences with courtship feeding by the male, followed by nest cleaning, and sealing by the female. Female lays about three eggs. The breeding season of the Tarictic started mid- March and ended in the end of July. Tarictics, too, lay about three eggs. The female leaves the nest hole at least 5 days before the last chick fledges. The nest hole occupied by the Tarictic soon after fledging of the Dulungan brood, breeding of the Tarictic in rock crevices and unsealed tree cavities concealed by adventitious roots and branches may indicate nest scarcity in some areas. The breeding females of both species moult their flight (and tail) feathers during the period of incarceration in the nest hole. Both species showed various behaviours during the breeding seasons. Nest concealment was demonstrated by the male, who remained vigilant, silent and for feeding did not visit the hole directly. However, when disturbed, the male alerted his mate by uttering alarm calls probably, making inmates climb the funk tree cavity above the nest. For direct observation, were acclimated within two hours in agricultural land, but in undisturbed areas, they could not be acclimated even after six days. In response to the newly constructed blind, the Tarictics responded vigorously by uttering loud alarm calls, and hovering over the hide. Only the male provided food to nestlings until fledging of the last chick. Before feeding, the male usually regurgitated first food items on a nearby branch. During fledging, the parents and fledglings showed a change in behaviour, and the male very often visited the nest without food provisioning. The nestlings stretched and flapped their wings, appeared in front of the nest hole and scanned the environs. The nestlings squeezed themselves through the nest opening and were welcomed by their parents waiting for their fledging. Habitat disturbance and threats to hornbills are related to socioeconomic conditions of inhabitants adjacent to the CPMR. People being poor depend on the natural resources of the forest. Swidden agriculture is a common practice that involves clearing of whole patches of vegetation, resulting in /loss. The poverty of locals and presence of permanent residences in the hornbill habitat pose threats to forest cover, hornbill populations and other wildlife species in the form of hunting, poaching, timber, firewood cutting, and exploitation of other resources. There is a dire need to continue conservation measures already started by PanayCon (formerly PESCP) in the form of conservation education and a nest reward scheme toward successful fledging. The local people around the CPMR should be granted incentives to reduce the pressure on natural resources, especially hunting, poaching and habitat destruction.

iii

Kurzfassung

Kurzfassung

Dies ist eine Studie über verschiedene ökologische Aspekte, mit Schwerpunkt auf der Nahrungsökologie und -konkurrenz, zweier philippinischer Hornvogelarten, der Dulungane (Korallenschnabel-Hornvogel) (Aceros waldeni) und der Tariktik-Hornvögel (Penelopides panini) während ihrer Brutzeit. Die Studie wurde in der Central Panay Mountain Range (CPMR), Philippinen, durchgeführt. Der Wald, durch Baumarten der Familien Dipterocarpaceae, Euphorbiaceae, Moraceae, Myristicaceae, Lauraceae, Sterculiaceae, Rubiaceae, Burseraceae und Acanthaceae beherrscht, kann in seiner Höhenstruktur von 90m über dem Meeresspiegel bis etwa 1900m variieren. Die Hauptstudienzentren bedecken eine Fläche von etwa 19km2, zwischen 11o 30.96′-11o 39.45′N und 122o 07.04′-122o 09.30′O, bei 100m bis 800m ü.M. Es wurden Feldstudien durchgeführt, um die Nisthöhlen, die von den beiden Arten gesäubert oder fast verschlossen werden, zu untersuchen. Beobachtungen, um das Verhalten der Hornvogelarten vollständiger erschließen zu können, wurden unternommen. Es wurden Daten zusammengestellt, die die verschiedenen Nistplatzeigenschaften und Hinweise auf eine Lebensraumzerstörung beinhalten sowie Faktoren, die die Hornvogelpopulationen beeinflussen. Statistische Tests wurden verwendet, wie die Spearman-Raug-Korrelation, Regressionsanalyse, der Kruskal-Wallis- Test gefolgt von mehreren Vergleichen, wie dem Clark und Evans Test, dem Rayleigh Test, dem Watson-Williams -'F-Test, und die Berechnung von dem Sörensen-Index, dem Horn-Index von Überschneidungen und dem Shannon-Wiener-Index. Insgesamt 157, Nesthöhlen aufweisende, Bäume wurden im Bereich der 19km2 der CPMR erforscht. Beide Hornvogelarten verwendeten 43 verschiedene Baumarten, die zu mindestens 18 Baumfamilien gehören, für den Nestbau. Dulungan und Tariktik verwendeten 27 bzw. 25 Baumarten, jeweils mit 35% Überlappung der Nistbaumarten. Zu den am meisten durch den Dulungan besetzten Nistbäumen, gehörten der Libtog, der Balakbakan (Shorea sp.) und der Tabaaw (Aglaia sp.). Die Nisthöhlenbäume, die durch den Tariktik besetzt wurden, gehörten zu den Baumarten: Libtog, Maganhop, Bagilomboy (Syzygium bordenii), Malabuyo (Alangium meyeri), Salong (Canarium asperum) und Toog (Bischofia javanica). 85% der Dulungan-Nester und 94% der Tariktik-Nester wurden in dem Hauptstamm gefunden. Beide Arten weisen Ähnlichkeiten im Nesthöhlenbau auf. Dulungan und Tariktik besetzten jeweils bis zu 73% und 87% der Nisthöhlen erneut. Die Nesthöhe über dem Boden stieg mit Zunahme der Höhe über dem Meeresspiegel. Es bestand eine positive Korrelation zwischen Nest Höhe über dem Boden und dem Umfang in Brusthöhe (BHD) von Nistbäumen. Die Nisthöhlen-Höhen waren zufällig, sowie der BHD eher normal, in dem Höhenbereich zwischen 100-700m ü.M. verteilt. Die Dulungan-Nisthöhlen waren höher über dem Boden als die Tariktik-Nisthöhlen. Die mittleren Höhen der Nisthöhlen über dem Boden des Dulungans und Tariktiks betrugen jeweils 11m, von 4m bis 20m, und ca. 7m, von 1m bis 18m. Es besteht ein höchst signifikanter Unterschied, in den medianen Nestloch-Höhen beider Arten. Wie bei der Nesthöhe, bevorzugt der Dulungan auch größere Bäume mit größeren Umfang. Der Dulungan und Tariktik verwendeten die Bäume mit einem medianen BHD von jeweils 224 cm, beginnend bei 120cm bis 665cm, bzw. 195cm, beginnend bei 96cm bis 323 cm. Dieser Unterschied war signifikant. Es gab keinen Unterschied in den mittleren Orientierungen der Nisthöhlen vom Dulungan (113o gegen die geografische Länge abgetragen im Jahr 2009 und 105o im Jahr 2010) und des Tariktik (113o in 2009 und 24o iv

Kurzfassung in 2010) in den beiden Jahren. Die Nisthöhleneingänge von beiden Arten während dieser beiden Brutzeiten waren gleichmäßig in alle Richtungen verteilt. Anders als in der Brutsaison 2009, unterschieden sich die mittleren Ausrichtungen der Nisthöhleneingänge des Dulungan und Tariktik-Hornvogels deutlich innerhalb der Brutsaison von 2010. Der Wert (R = 0,839 im Jahr 2009 und R = 0,752 in 2010) des Clark und Evans-Testes während der beiden Brutsaisons zeigt eine deutliche Abschweichung von Zufälligkeit in Richtung einer Klumpung der Dulungane. Im Gegensatz dazu zeigten die Tariktiks eine Tendenz in Richtung einer regulären Dispersion (R = 1,268 in 2009 und R = 1,086 in 2010), die ein Hinweis auf eine größere Territorialität ist. Die gesamte, erfassbare Nistbaumdichte beider Spezies wurde auf 8.267/km2 berechnet. Die gesamte, erfassbare Nistbaumdichte beider Hornvögel während der Brutzeit 2009 und 2010 betrug 6,67/km2 und 9,7/km2. Die Brutpaardichte des Dulungan und des Tariktik wurde in der CPMR auf jeweils 4.47/km2 bzw. 5.83/km2, sowie eine Population von 1787 Brutpaaren von Dulunganen und 2333 Brutpaaren von Tariktiks, geschätzt. Die Dulungane wurden zwischen 280m und 800m ü.M. aufgezeichnet, und die Tariktiks zwischen 100m und 610m ü.M., jedoch beschränkten sich die meisten der Dulungan- und Tariktik- Populationen jeweils auf Flächen zwischen 450-600m ü.M. und 400-550m ü.M. Es gab keine Hinweise auf einen Unterschied in der Anzahl der Brutpaare der beiden Arten bei Konstanthalten der Höhen über dem Meeresspiegel. Die durchschnittliche Anzahl der Fruchtarten, die aus den Nisthöhlen beider Arten während der beiden Brutsaisons gesammelt wurden, betrug 6,2. Die maximale Anzahl Fruchtarten, die so aus den Nisthöhlen stammten, betrug 17 bei den Dulungan- und 13 bei den Tariktik-Brutpaaren. Die Früchte gehörten etwa 24 Familien, 31 Gattungen und 52 Arten an. Die häufigsten Arten gehörten zu den Familien Myristicaceae, Myrtaceae, Palmae, Moraceae und Meliaceae. Beide Nashornvögel nutzten insgesamt 52 Obstarten, die Dulungane 51 Arten und die Tariktik 38 Fruchtarten, mit einer Nahrungsüberlappung von Is= 83 Prozent. Da beide Hornvögel syntop sind und die gleichen Fruchtvorkommen verwenden, sowie eine sehr hohe Nahrungsüberlappung vorliegt, kann man davon ausgehen, dass die beiden Arten in starke Konkurrenz, bezüglich gleicher Fruchtsorten, während einer Nahrungsverknappung, miteinander treten könnten. Der Mittelwert der zwischenartlich kürzesten Nachbarabstände im Gesamtgebiet und der mittlere Prozentsatz der Nahrungsüberlappung beider Arten ergaben 157m und 39%, und es war eine hoch signifikante negative Korrelation zwischen den beiden Parametern zu erkennen. Die Fruchtarten, die häufiger von den Dulunganen, während der zwei Brutzeiten, verwendet wurden, waren Uya-oy (Planchonia spectabilis), gefolgt von Pili (Canarium sp.) und Maguhansol (Sandoricum koetjape). Meliaceae, Myristicaceae und Lecythidaceae waren bevorzugte Familien der Dulungane. Fruchtarten, die häufiger von den Tariktikvögeln konsumiert wurden, waren Pili (Canarium sp.), Uya-oy (Planchonia spectabilis) und Bugohansol (Prunus fragrans). Die am meisten bevorzugten Fruchtfamilien des Tariktik, während beider Saisons, gehörten den Sapotaceae, Myristicaceae und Burseraceae an. Die Diversitätsindizes zeigen, dass die Dulungane mehr Generalisten, in Bezug auf Fruchtverzehr, sind, als die Tariktikvögel. Die Dulungane sind während der Brutzeit fast ausschließlich von Früchten abhängig wohingegen die Tariktikvögel ihre Nahrung durch tierische ergänzen. Die intraspezifische Überschneidung Nahrung engst benachbarter Brutpaare des Dulungan und Tariktik, reichten jeweils von 0-100% und 22-100%. Keine oder eine sehr geringe Nahrungsüberschneidung von Bruten der gleichen Spezies, könnte ein Hinweis auf Fruchtknappheit und Ressourcenaufteilung sein, um intraspezifische Konkurrenz zu v

Kurzfassung mindern. Die Bruten des Tariktiks zeigten während der Zeit des Ausfliegens, dass die Ernährung zu 97,5% aus Früchten und 2,5% tierischer Nahrung bestand. Männliche Hornvögel brachten Früchte einer einzigen Spezies, hin und wieder ergänzt durch tierische Nahrung, die aus Eidechsen, Heuschrecken, Käfern, Fliegen und anderen Insekten bestand. Die mittlere Anzahl der Besuche und die von Nahrungsstücken pro Tag betrug jeweils 9,8 und 189. Die mittlere Anzahl von Nahrungsstücken pro Besuch war 19,4. 66,7% der Fütterbesuche enthielten nur Früchte, und 18% enthielten sowohl Früchte, als auch tierische Nahrung, während bei 15% ausschließlich diese gebracht wurde. Im Gegensatz zu intraspezifischer Nahrungsüberlappung, beträgt die interspezifische zwischen Tariktik und Dulungan höchstens 66%, und die Korrelation zwischen dem nächstgelegenen Nachbarschaftsabstand beider Arten und die Nahrungsüberlappung waren ebenfalls sehr schwach. Dies könnte auf eine Verschiebung bei der Nahrungswahl hindeuten, um die Konkurrenz um Nahrung zwischen zwei Arten zu vermindern. Der Zeitpunkt der Fortpflanzung kann in verschiedenen Gebieten und von Jahr zu Jahr variieren. Der Dulungan begann in der Regel Anfang März zu brüten, und das Ausfliegen fand gegen Ende Juni und Anfang Juli statt. Die Fortpflanzung beginnt mit einem Balzfüttern, gefolgt von Nestreinigung und -verschließung durch das Weibchen. Die Weibchen legen etwa drei Eier. Die Brutzeit der Tariktiks begann Mitte März und endete gegen Ende Juli. Auch die Tariktiks legen etwa drei Eier. Das Weibchen verlässt die Nesthöhle mindestens 5 Tage bevor das letzte Kücken flügge wird. Dass die Tariktiks die Nisthöhlen der Dulungane nach deren Ausfliegen besetzen, sowie das Brüten in Felsspalten und unverschlossenen Baumhohlräumen, die zufällig durch Wurzeln und Äste verborgen sind, könnte das Ergebnis von Nestknappheit in einigen Regionen sein. Die brütenden Weibchen beider Arten mausern ihr Groß- (einschließlich Schwanz-) Gefieder während ihres Höhlenaufenthalts. Beide Arten zeigten verschiedene Verhaltensweisen während der Brutzeit. Es hat sich herausgestellt, dass die Nesttarnung vom Männchen übernommen wurde, das bei Störung lautlos blieb und die Höhle zum Füttern nicht direkt anflog. Wenn sie allerdings stärker gestört wurden, alarmierte das Männchen seine Partnerin durch Alarmrufe, so dass die Insassen sich in die Rückzugshöhle über dem Nest begaben. Bei der direkten Beobachtung (wurde festgestellt, dass) der Vogel sich innerhalb von zwei Stunden in landwirtschaftlichen Flächen an die Störung gewöhnen konnte, jedoch in unberührten Gebieten nicht einmal nach sechs Tagen. Als Reaktion auf eine neu errichtete Blende, äußerte der Tariktik energisch laute Alarmrufe und rüttelte darüber. Nur das Männchen versorgte die Nestlinge, bis zum Ausfliegen des letzten Kückens. Vor der Fütterung erbrach das Männchen in der Regel zunächst die Nahrung nahe der Höhle. Während der Ausflugsphase zeigten die Eltern und Jungvögel eine Änderung im Verhalten, und das Männchen besuchte sehr oft das Nest, ohne (die Jungvögel) mit Nahrung zu versorgen. Die Nestlinge streckten ihre Flügel und schlugen damit, erschienen vor der Nisthöhle und erkundeten die Umgebung. Die Nestlinge zwängten sich durch die Nestöffnung und wurden von ihren Eltern “begrüßt”, die auf ihr Ausfliegen gewartet hatten. Beeinträchtigungen des Lebensraumes und Bedrohungen der Hornvögel stehen im Zusammenhang mit den sozioökonomischen Bedingungen der Bevölkerung, die den CPMR umgibt. Die Menschen, die in ärmlichen Verhältnissen leben, sind auf die natürlichen Ressourcen des Waldes angewiesen. Brandwirtschaft ist eine gängige Praxis, die das Zerstören der gesamten Vegetation einer Fläche bedeutet, und somit die vi

Kurzfassung

Zerstörung bzw. den Verlust von Lebensräumen beinhaltet. Die Armut der Einheimischen und das Vorhandensein von ständigen Wohnsitzen im Lebensraum der Hornvögel bedrohen den Wald, die Hornvogelpopulationen und andere Wildtierarten, z.B. durch Jagen, Wilderei, Abholzung, Brennholzbesorgung, und Ausbeutung anderer Vorkommen. Es besteht ein dringender Bedarf an Erhaltungsmaßnahmen, die bereits von PanayCon (ehemals PESCP) in Form von Umwelterziehung und einem Nestbau - Belohnungs- programm, das erfolgreiches Ausfliegen belohnt, begonnen wurden. Die Menschen vor Ort rund um die CPMR sollten Anreize bekommen, um die die natürlichen Ressourcen belastenden Faktoren, vor allem die Jagd, Wilderei und die Zerstörung von Lebensräumen, zu reduzieren.

vii

Introduction

Chapter 1 INTRODUCTION

Hornbills are one of the most (distinct) noteworthy groups of birds in the Old World tropics (Kemp, 1995). They are among the largest birds in tropical lowland forests (Kinnaird & O'Brien, 2007), and occupy extremes of habitat, from moist evergreen forests that measure their rainfall in meters to arid steppes where every millimetre of rain is precious (Kemp, 1995). They are boldly coloured, utter distinctive loud calls, and are noisy in flight, making them very noticeable to human observers as compared to other birds (Delacour & Mayr, 1946; Kemp, 1995; Kinnaird & O'Brien, 2007). They are prominently unusual in appearance, having peculiar features like a disproportionate form and shape, jerking of the head when making loud, distinctive calls, and nesting in the natural cavities of trees (Poonswad, 1991).

Hornbills differ from all other birds in having a number of common characteristics, which are expected to be evidence of their relatedness and common ancestry. The most prominent of these characteristics is the development of a casque on the upper mandible of the bill, not found in other species. Hornbills are large birds with a small face (Delacour & Mayr, 1946; Poonswad, 1991) and widely differ in size and mass. They range in mass from 4119g for male turkey-sized Bucorvus ground hornbills (Bucorvus leadbeateri) of South African Savannas to 83g (the fifty times less) for female, dove- sized dwarf Black Hornbill (Tockus hartlaubi) of the African evergreen forest (Kemp, 1995). Hornbills possess an enormous bill, of bright colours, and usually ornamented above with a hollow casque (Delacour & Mayr, 1946). From this prominent and unique structure of decurved bill and casque, hornbills derived their names, and were assigned to the avian order , known as Bucerotidae (Kemp, 1995).

Apart from these morphological characteristics, the hornbills are also unique in having different internal anatomy such as possessing the first two neck vertebrae that support the skull, the axis and atlas, fused together. They possess an accessory supraoccipital condyle, which stops the head from being jerked back too far. Their kidneys are separated into two lobes, thus lacking the third middle lobe that is present in all other bird species. All but two species of hornbills have the habit of nest sealing during the breeding season. These common characters lead to the assumption that hornbills are monophyletic.

1

Introduction

Hornbills have been placed into two families, Bucorvidae and Bucerotidae on the basis of 26 characters of anatomy, behaviour and development (Kemp, 1995). The two ground hornbills of the family Bucorvidae is an earlier surviving offshoot, evident as mid- Miocene fossil from Morocco some 15 million years ago (Olson, 1985). The rest of hornbill species lack credible fossil record and have been placed in the family Bucerotidae (Kemp, 1995). The genera can be easily distinguished, but the relationships between them are still to be established. Initially 14 genera of hornbills were recognized (Sanft, 1960), which, based on the cladistic analyses of relationships, were rearranged and reduced to nine genera (Kemp & Crowe, 1985), some of which in turn possess sub-genera recognizable by further characteristic details.

1.1 General distribution

Hornbills are distributed throughout the Old World (Kemp, 1995), occurring across sub- Saharan Africa, through India and southern Asia, the Sunda Shelf islands of , extending through New Guinea and ending in the Solomon Islands (Fig. 1. 1).

Fig. 1. 1. World distribution map of hornbill species (Source: Kemp, 1995)

There are 54 species of hornbills among 14 genera (Kemp 2001) of families Bucorvidae and Bucerotidae (Kemp, 1995). The Bucorvidae contain two species of African Bucorvus ground hornbills, and the Bucerotidae comprise of the remaining 52 species, which are 2

Introduction referred to as “typical” hornbill genera (Kinnaird & O'Brien, 2007). There are 23 hornbill species in Africa, in which 13 (57%) live in deciduous woodland or savanna with the remainder living in tropical evergreen forests. Among Asian hornbills, only the ( birostris) inhabits savanna woodlands. The remaining 30 Asian hornbill species living in the forests are mostly confined to tropical lowland forests. Forest dwelling hornbills of Asia have a large range requirements for individuals and family groups that require large areas of pristine habitat (Sanderson et al., 2002), and have a significant impact on the structure and function of natural ecosystems (Kinnaird & O'Brien, 2007).

There are five species belonging to the Aceros. The Rufous-necked Hornbill occurs in Nepal, Vietnam, and Bhutan. The Wrinkled Hornbill is distributed in , Borneo, and Sumatra. The Red-knobbed Hornbill is endemic to the Wallacean island of . The Writhed Hornbill and the Rufous-headed Hornbill (Aceros waldeni = Dulungan) are endemic to various islands of the Philippines (Kinnaird & O'Brien, 2007).

The genus Penelopides, known as Tarictic Hornbills, is represented by five species, which are restricted to the Philippines and Sulawesi. The Sulawesi Tarictic Hornbill is endemic to the island of Sulawesi. The Mindanao Tarictic Hornbill, the Visayan Tarictic Hornbill, the Mindoro Tarictic Hornbill, and the Luzon Tarictic Hornbill are endemic to various Philippine islands (Kinnaird & O'Brien, 2007).

1.2 Feeding behaviour

All Hornbills are omnivorous birds, consuming at least 60 species of fruits and 70 species of (Delacour & Mayr, 1946; Tsuji, 1996), except Bucorvus ground hornbills, which are entirely carnivorous, and wattled Ceratogymna hornbills of Africa or Wreathed Aceros hornbills of Asia, which are largely frugivorous (Kemp, 1995). Their favourite food is figs but when raising the young, they prey on insects and small animals, putting the hornbills number one in the food chain (Poonswad, 1991). The wide range of vertebrates and invertebrates, delivered to nests and the lack of any obvious specialized adaptations for predation suggest hornbills are opportunistic omnivores rather than dedicated or even clever carnivores (Kinnaird & O'Brien, 2007). The feeding and breeding requirements are driving forces that determine how hornbill species locate and consume preferred food, and where to place their nests. The dynamic nature of resources

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Introduction such as fruiting and nest tree availability for a variety of hornbill species determine the movements, social structure, breeding season, productivity, and moult (Kemp, 1995).

Asian hornbills are dedicated fruit consumers but supplement their diet with animal food. Diet selection has a great impact on the daily activity budget, foraging strategy, and territorial behaviour. The hornbills’ food includes berries, drupes, figs, and dehiscent capsules or pods. Berries include fruits like blue berries, tomatoes, and grapes that have soft exteriors and watery, fleshy pulp (Kinnaird & O'Brien, 2007). Drupes include avocados, peaches, and olives with a tough membrane surrounding a large stone-like seed. Depending on the size, drupes may be swallowed whole or torn, and eaten bit by bit. Dehiscent pods have dry, generally hard and inedible outer coverings that split on both sides when ripe. The pulp of many dehiscent fruits contrasts strongly with the colour of the pod and may be reduced to a thin coating or aril covering the seeds. Nutmegs are characterized by dull brown pods that dehisce to expose brilliant red arils, and some form intricate lacy nets over a seed (Kinnaird & O'Brien, 2007). Hornbills probably satisfy their need for water from the moisture contents of fruits. The control of salts in the blood stream of carnivorous species whose diet is rich in salts is of very much interest. Unlike the predatory species, hornbills lack special glands, which assist the kidneys in secreting excessive salts. There might be some other structure and mechanism involved, and a special bi-lobed kidney may have unusual properties (Kemp, 1995).

Hornbills leave their roosting site early in the morning followed by preening, stretching, and territorial calling. In some species, especially the frugivores which roost communally, the first birds leaving the area may stimulate others, especially the less experienced to follow the well-experienced birds to fruiting trees. Depending on the species, the distance toward feeding area may be travelled singly or as many as a whole communal flock of several hundred birds together. The location of food and time invested in feeding depend on the distance, density, and dispersion of the preferred diet of each species. Hornbills should invest more time if food is dispersed evenly while less time should be invested if food has a patchy distribution. The resource distribution may affect the behaviour of hornbills (Kemp, 1995).

The feeding can take place at any time of the day and depends on habit and foraging abilities of species and individual. The feeding method includes from a simple picking up a food item to more complex and energetic feeding like levering over object, digging into the ground, snatching, swooping, plucking and hawking. Food items are manipulated in 4

Introduction different ways. They are simply swallowed whole by tossing a food item back from the bill tip into the throat. Some items are stripped of extraneous parts before being swallowed, such as fruits of their skins or insects of their wings and legs; some are softened before swallowing by passing them through and crushing them in the bill or cleaned of unwanted covering by being wiped back and forth over a perch or along the ground. Sometimes instead of swallowing, the food is for courtship feeding (Kemp, 1995; pers. obs.). Fruits offer two basic types of energy rewards: carbohydrates in the form of sugars and starch, and lipids in the form of fatty acids. Lipid rich drupes and pods typically offer a higher quality energy source than berries and figs. This is because fats contain approximately 9cal/g versus 4cal/g dry weight for sugars (Robbins, 1993). Simple sugars are water-soluble and readily absorbed in the gut by both passive and active uptake (Kinnaird & O'Brien, 2007).

1.3 Reproduction and sexual behaviour

Hornbills exhibit a particular breeding season or rhythm, which is governed by the success with which each pair produces recruits to the next generation (Kemp, 1995). Hornbills, nesting in the equatorial region of Malaysia, Indonesia and the Philippines, experience seasonal and aseasonal climates. Species in aseasonal areas typically enter their nests over a span of four to six months. In seasonal equatorial areas, there are two patterns. On Sulawesi, Sulawesi Tarictic Hornbills nest during the rains, and Red- knobbed Hornbills nest during the transition between rains and the dry season. In the Philippines, hornbills begin nesting during the dry season (Kinnaird & O'Brien, 2007). The breeding season of Dulungan commences in early March, and that of Tarictic Hornbills about four weeks later in March and early April (Kauth et al., 1998; Klop et al., 1999).

After sealing herself, the female waits for 4-6 days or even weeks, the maximum record of 24 days before starting to lay. The pre-laying interval after sealing the nest, and the inter egg interval within clutches are shorter when food is abundant. Incubation begins with the first egg and eggs hatch at approximately the same intervals as they were laid. The larger chick has an advantage of dominance that can result in the starvation of the smallest chick during the shortage of food. The clutch size and egg size vary with the body size of each species. Larger species have one or two eggs and smaller species may have up to eight eggs per clutch. Dulungan and Tarictic have a maximum clutch size of 3 5

Introduction eggs, and a brood size of 2-3 at fledging has been reported (Kemp, 1995; Kauth et al., 1998; Klop et al., 1999; pers. obs.). The egg shape is oval, rather elongate with a white pitted shell that is stained as incubation proceeds. The larger species tend to lay eggs 3-5 days apart while smaller species lay on consecutive or alternate days (Kemp, 1995).

An integral part of hornbill biology, essential to their survival, is regular replacement of feathers by moulting, which occurs more or less on an annual basis. Juveniles of some species undergo a partial moult of fluffy head and neck feathers between the period of nest leaving and first full moult into adult plumage at about one year of age. Moults of smaller species of hornbill are most regular, most frequent, and shortest in duration while in larger species, a complete replacement of all feathers may spread over several years. A unique attribute of the hornbills is that the moulting takes place during the breeding season that puts an extra nutritional burden on a hornbill (Kemp, 1995). Breeding females of many species undergo a simultaneous moult of all major flight feathers (the remiges and rectrices) with the sequential moult of body feathers. Breeding females of Dulungan and Tarictic moult their flight feathers in the nest hole during the breeding season (pers. obs.). Males may undergo moult during breeding or suspend it until late in the breeding cycle, when foraging demands on the male are reduced. Non-breeding adults and juveniles may also moult during the breeding season when other members are breeding (Kemp, 1995). Complete moult of flight feathers or rectrices by females during nesting is highly variable (Kinnaird & O'Brien, 2007). Even the same species may experience complete moult, no moult or partial moult (Poonswad et al., 1983; Kannan & James, 1997).

The breeding female does not moult its belly feathers, but the abdomen is unfeathered, which is directly placed against the eggs. In smaller species, moult is usually confined to a specific season, larger species or those with no obvious seasons may moult anytime of the year. In some species, the female either suspends moult during breeding or drops a few feathers sequentially, and regrows them before dropping more. In most species, the breeding female may simultaneously shed all primary, secondary, and tail feathers with or soon after the start of egg laying. Breeding females have also been found with complete flight-feather moult or with no moult. There might be a link between nutritional condition and exact timing, pattern and rate of moult (Kemp, 1995). The stage of moult has a significant effect on energy expenditure of the incubating female and corresponds with duration of incubation (Klaassen et al., 2003). 6

Introduction

Soon after sealing, the female starts incubation with the first egg (Kemp, 1995). In Asian hornbill species, incubation periods range from 16 days for cooperatively breeding Sulawesi Tarictic Hornbill to 51 days for the Helmeted Hornbill (Kinnaird & O'Brien, 2007). Incubation period for Visayan Tarictic ranges from 30-35 days (Buay, 1991; Klop et al., 2000). This incubation period may depend on egg size rather than on body size as big birds lay bigger eggs that take a longer time to develop (Kinnaird & O'Brien, 2007). In case of any danger, the female will bolt up in the funk hole that exists above the majority of nests. In this way, the female and later the chicks often disappear completely from sight and are beyond the reach of predators. The male and other cooperative breeders feed the incubating female. Food items carried singly or as a bundle in the bill, or collected in the gullet, is fed to the female (Kemp, 1995).

The hatching takes place in an interval with the sequence corresponding closely to when the eggs were laid. A newly hatched chick is altricial, pink-skinned, naked, eyes closed, and with the prominent egg-tooth on the upper mandible. Nestling period of Dulungan ranges between 42 to 60 days (Kauth et al., 1998) and of Tarictic between 54 to 58 days (Klop et al., 1999; 2000). The nestlings respond to auditory and tactile stimuli and beg for food, which is placed whole in its bill by the female. An air sac develops under the skin of the shoulder region that within days spread to other body parts to develop an extensive system of air sacs, which can function as thermal insulation and mechanical protection. The feather-quills emerge at about the time that the eyes begin to open. They emerge first on the breast, then on the back and wings, then on the head and tail and finally on the neck. The feather development is shared with the related families of the hoopoes, rollers, kingfishers and bee-eaters (Kemp, 1995).

Female and/or a chick, breaks down the nest sealing by hard pecking with the bill, which may take from a few hours to several days. After fledging, the chick remains near the nest for a few days, among the dense cover and continue to be fed by male. Juveniles may stay with their parents for a month, or in cooperatively breeding species even up to after attaining sexual maturity. The interval between fledging and start of breeding varies from less than one year in small hornbills to at least 4-6 years in the larger species (Kemp, 1995).

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Introduction

1.4 Nesting Habit

All hornbills are hole nesters and prefer nests in the big tree hollows. The unique breeding behaviour that makes hornbills prominent and different among other bird species is that the female incarcerates herself by sealing the nest opening, leaving a narrow vertical slit for providing food by the male to the breeding female and nestlings. Using these nest hollows, each species has its own strategy in raising its chicks safely (Kemp, 1995; Tsuji, 1996). Two species of ground hornbills do not seal their nests and may use natural holes, excavate their own holes or even use stick-nests of other species (Kemp, 1995).

Nest site selection and preparation aim to provide a suitable breeding environment. The nest site must be defendable against other hornbills and other hole living animals, and the cavity must have suitable microhabitat for incubation of eggs and rearing of the young. The cavities are checked by both members of a pair, especially the female by going around and poking her head into holes. Nest selection can occur at any time during the year in territorial pair but usually at the beginning of the breeding season in non-territorial species (Kemp, 1995).

The nest cavity sealing of hornbills possibly promotes very low nest predation rates (Klaassen et al., 2003) and is important in preventing attacks from conspecifics, apparently in competition for scarce nest holes. When a female agrees to use the nest cavity, she begins to seal the nest opening and spends time in the nest. Male and/or group members continue feeding, and bring her sealing and lining material. Sealing is applied with broad, flattened side of the bill by side-to-side vibration of skulls resulting in a series of layers. The male attempts to copulate with the female after she emerges from the nest during the sealing process (Kemp, 1995; Tsuji, 1996). It is mostly the female that seals the hole. The plaster consists of , tree bark, wood dust, and food debris. The proportion of materials varies from species to species. The female mixes the material with her own faeces or regurgitated food. A narrow, vertical opening is left in the plaster, through which the male feeds, and the female and the brood defecate (Poonswad, 1991; Kemp, 1995). Besides sealing material, the male also brings lining to the nest. Depending on the species, the lining material may include green leaves, grass, bark flakes, and dry leaves. Lining is used for levelling the nest floor, which may be augmented by food remains such as fruit seeds, moulted feathers and material chipped off from the nest wall. The lining acts as an absorbent of faecal matter and may encourage insects to keep the

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Introduction nest clean or reduce parasites and pathogens (Kemp, 1995). From the time the nest is sealed until the chicks fledge, the female and the brood are wholly dependent upon the male. The breeding cycle varies from species to species (Poonswad, 1991). Hornbills get rid of excreta and food remains in a hygienic fashion. Ground hornbills, which do not seal their nests, often defecate away from the nest during the short break. The majority of species squirt their excreta with considerable force out through the nest opening. Food remains, within the nest are tossed from the nest. The other debris, such as soiled lining and moulted feathers are also thrown out of the nest opening (Kemp, 1995).

Hornbills and all their close relatives in the are unable to excavate their own nests. Only some of the bee-eaters manage to dig their own cavities because they nest in soft banks. Hornbills are forced to rely on cavities created by excavators like woodpeckers and barbets, or natural cavities that form after the branches break or after other injuries are inflicted upon forest trees. Because they are large-bodied, Asian hornbills require big, mature trees for adequately sized cavities. The size requirements alone are thought to limit the availability of suitable cavities (Poonswad, 1995; Kemp, 1995; Mudappa & Kannan, 1997) and if so could play a major role in population dynamics.

During the incubation period, the female is walled into the nest (Delacour & Mayr, 1946), and the well-insulated nest hole with thick walls helps in maintaining the internal temperature of the cavity, by delaying rise in temperature when the sun rises until later in the day; and heat absorbed during the day delays drop in temperature during the night (Kemp, 1995). Factors that affect the availability, suitability, and durability of nest cavities, such as a pattern of breakage, rotting, and mortality in different tree species, may also affect hornbill numbers and breeding success in different habitats (Kemp, 1995).

Asian hornbills live only in tropical forests, which provide nest trees and food resources. A forest containing hornbills must be large and unaltered by man. Dipterocarps are favourite nesting trees for all hornbills. Scientists speculate that fungi, which cause the heart and butt rot in dipterocarps, eventually create the ideal nest cavity for the hornbill (Poonswad, 1991).

In territorial species, the nest sites are evenly spaced, but in non-territorial species nests may be clumped with short distance in between the nest sites. All hornbill species guard the area against invaders of their own species or other species, but larger feeding

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Introduction territories are usually defended against the members of the same species. As many as eight species of hornbill may coexist within an area; however, nests of different species may end up within a few meters of one another. Two Tockus species may even have their nests in different holes in the same tree alongside owls and squirrels (Kemp, 1995).

1.5 Scope of the present study

Among 54 hornbill species, the Philippines harbour nine species (17%) of the world and 29% of Asian hornbills (Kemp, 1995; Kinnaird & O'Brien, 2007). All species found in the Philippines are endemic and confined to some islands of the archipelago. There are about 15 endemic species and subspecies distributed largely in lowland rainforest, which follows the general biogeographic pattern within the archipelago, with endemic bird areas formed by Pleistocene island aggregation (Bibby et al., 1992; Gonzalez, 2007).

The central Philippine islands of Panay, Negros, Cebu, and Masbate are unique in comprising of the divergent fauna that supports a high proportion of endemic species (Dickinson et al., 1991; Bibby et al., 1992) and are a focus of highest conservation priority of the World Conservation Union (Dinerstein et al., 1995). Two species, namely Dulungan (Aceros waldeni) and Tarictic (Penelopides panini) occur in the Central Panay Mountain Range, and are being studied by PanayCon (formerly Philippine Endemic Species Conservation Project (PESCP) run by Prof. Dr. Eberhard Curio managed by PhilinCon.

Dulungan (Aceros waldeni), a critically endangered and endemic to the Philippines on the island of Panay has a severely fragmented, remaining population. It is known historically from three islands, Panay, Guimaras and Negros. Extensive loss of low to mid-altitude forest and hunting has resulted in an extremely rapid and continuing population decline (Collar et al., 1994; BirdLife International, 2001). Given very small, severely fragmented and rapidly declining populations as a result of lowland deforestation and hunting, Tarictic (Penelopides panini) formerly known as a critically , has been elevated to Endangered status (Collar et al., 1994; BirdLife International, 2001).

The forest tree species can be potentially at risk if only a small number of frugivores visit them. Among these frugivores, many endangered species of hornbills are mostly the dispersers of trees, in the absence of these large avian frugivores the composition of the mature forest will change drastically. Hamann & Curio (1999) have estimated that 60% of

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Introduction all late-successional species would lose all dispersal agents if large avian frugivores are hunted to extinction. Tree species like Myristica ceylanica, Pometia pinnata, and Aglaia sp. depend solely on the two species, Dulungan and Tarictic hornbills for seed dispersal (Hamann & Curio, 1999). The population and breeding status of hornbills make them excellent indicators of the health of the forests they inhabit. Any tropical forest with large, secure populations of hornbills is ecologically intact (Poonswad, 1991).

The measures taken for the conservation of any organism involve identification of factors that affect the population growth. Various factors may limit growth, at temporal and spatial scales. Evaluation of population limitations and conservation measures entail adequate monitoring of population dynamics (Goldsmith, 1991). For a sustainable population, hornbills require sufficient food and safe nest sites, as provided by intact forests and large tree cavities (Poonswad & Tsuji, 1994; Kemp, 1995; Poonswad, 1995; Liewviriyakit et al., 1999; Kinnaird & O'Brien, 2007). These cavities are made by natural processes and hornbill species often compete among themselves and with other organisms for such sites (Poonswad et al., 1987; Poonswad, 1995; Chuailua et al., 1998), which are likely to be limited, depending on the habitat and territorial behaviour of species (Kemp, 1995).

Interspecific and intraspecific competition may occur for food resources as a strategy that mitigates intra as well as interspecific dietary overlap. Territorial defence effectively rules out competition by conspecifics and defending species may monopolize food trees within their territory (Kinnaird & O'Brien, 2007). Competition between organisms may be a consequence of exploitation where one individual depletes resources and leaves less for another individual, or interference, where an individual inhibits the access of another individual to a resource (Schoener, 1983). Interference competition may be active, arising deliberately due to aggression (Kotrschal et al., 1993) or kleptoparasitism between individuals (Brockmann & Barnard, 1979), and avoidance of competitors to reduce the number of encounters (Baker et al., 1981).

Understanding the basic biology of hornbills, especially those with critical population status, is a prerequisite for maintaining sustainable populations and habitat, and involves regular fieldwork for population assessment and ecosystem health. A sustainable food supply is critical for sustainable population that determines the present and future picture of the fate of hornbills. Previous studies (Curio et al., 1996a; Kauth et al., 1998; Klop et al., 1999; Klop et al., 2000; Curio, 2005) of sympatric Dulungan and Tarictic hornbills, 11

Introduction focusing on different ecological aspects, were conducted separately without considering coexistence of both species. No comprehensive comparative study on these two sympatric species has been conducted simultaneously to evaluate various ecological aspects, especially competition for resources for their coexistence. The present study was designed to understand some ecological aspects of these two sympatric species, Dulungan and Tarictic, endemic to Panay island, with special reference to competition for resources during their breeding seasons, aiming at the following objectives:

Objectives of the present study

1. To study the feeding ecology and competition for food in two (syntopic) sympatric Philippine hornbill species, Dulungan and Tarictic Hornbill, during their breeding seasons.

2. To determine the nest site characteristics and degree of overlap and comparison of nest tree characteristics, and competition between the two species for the same nest resources.

3. To examine the dispersion pattern of active nest holes of Dulungan and Tarictic breeding pairs.

4. To find out breeding pair density/population status of the Dulungan and the Tarictic. Do the two species segregate (statistically) in terms of elevation and avoidance of nearest neighbours?

5. To determine whether Tarictics’ breeding about a month later than the Dulungan (segregation in time) can be interpreted on the basis of interspecific competition for the same food resources.

6. To describe the breeding biology and various behaviours of the two sympatric species.

7. To find out the factors affecting hornbill populations and their habitat

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Materials and Methods

Chapter 2 MATERIALS AND METHODS

2.1 Study area

The present study was conducted in the Central Panay Mountain Range (CPMR) on Panay Island, Philippines. The mountain range stretches over 100km from north to south along the border between Antique Province and Aklan, Capiz and Iloilo Provinces.

The CPMR has several high peaks, including Mt-Madja-as (2,110m asl) and Mt Nangtud (2,073m) in the north, Mt Baloy (1,728m) in the centre and Mt Inaman (1,585m) in the south. The mountain range retains the extensive forest cover, and has been proposed as the Central Panay Mountain National Park. The main habitat is montane forest, including mossy forest at about 1,400 to 1,900m, and some areas possess lowland forests in the steep gullies on the lower slopes between 200 and 900m or in some areas the forest may reach down as low as 90m above sea level (asl) (Mallari et al., 2001).

The mountain range area is blessed with the threatened and restricted-range species of the Panay Endemic Bird Area. The forests on the lower slopes of the mountains support important populations of several of the lowland and lower montane endemic species. Several lowland forest species have important populations, notably of Visayan Tarictic Hornbill and Writhed-billed Hornbill (Mallari et al., 2001).

The core study area is located in the northern part of the CPMR, comprising specifically part of Barangay Alegre and Igpatuyao of the Municipality of Sebaste, and Barangay Calabanog of the Municipality of Pandan. The study sites embrace rugged terrain, covering an area of 19km2, between 11o 30.96′-11o 39.45′N and 122o 07.04′-122o 09.30′E, ranging in elevation from 100m to 800m asl (Fig. 2. 1).

Most parts of the study area possess primary forest with relatively (undisturbed) intact vegetation especially on steep slopes, comprising of multi-storeyed broad-leaved evergreen and semi-evergreen vegetation with epiphytes and lianas. Dominant species in the habitat of hornbill belong mostly to the family Dipterocarpaceae, Euphorbiaceae, Moraceae, Myristicaceae, Lauraceae, Sterculiaceae, Rubiaceae, Burseraceae, Acanthaceae (App. 1). The moist areas along the streams have plenty of bamboo vegetation. Palm and banana trees are also planted in the moist areas. Locals use the bamboo and canes extensively for the construction of their houses and domestic articles. 13

Materials and Methods

Fig. 2. 1. Map of Panay Island showing the location of the study area

The forests near human habitation are under enormous pressure of human-related activities that result in disturbance and degradation, especially due to the clearing of forest trees for agriculture. These clearings are used for banana and palm plantation, upland rice cultivation, sugar cane, maize and vegetable production. Some of the degraded primary forests have been replaced by secondary growth. The gaps produced in the contiguous forest due to these human-related activities are leading to forest fragmentation. Forest patches are interspersed with denuded hillsides, which along with edaphic and geological conditions and gravity are the main causes of land sliding in the area. Some areas possess deep loamy soil, humus and leaf litters while others possess rocky areas of limestone having deep cracks due to weathering. The areas along the streams have bare igneous rocks. Some rocky areas have shallow top soils with sparse vegetation. 14

Materials and Methods

The area is blessed with steep slopes, enormous small and large water streams and rivers which are flooded during heavy rain. Some of the main rivers joined by the tributary water channels are Bacalan River, Bajo River, Apayo River, Calacala River, Ibajay River, most of which flow from east to west and drain directly into the Sulu Sea. The areas along the rivers and streams possess most of the nest holes of hornbills.

The climate is hot and humid, though nights are cool in forest areas. Most of precipitation is received during the monsoon season. The area also experiences tropical storms that lead to uprooting of old tall trees. The decomposition rate seems to be very high and fast. Big fallen logs and even standing dead trees experience rapid decomposition.

2.2 Methods

2.2.1 Field survey and species identification

A study on feeding ecology and competition for food in two Philippine hornbill species, Dulungan (= Writhed-billed Hornbill) (Aceros waldeni) and Tarictic Hornbill (Penelopides panini) during their breeding seasons of 2009 and 2010 was conducted in the Central Panay Mountain Range (CPMR), Philippines. Extensive surveys of the study area were conducted to explore the nest holes occupied by the two species. Sealing of nest hole was a clear indication of occupation of the hole by hornbill species, further identification to species level was made by regular surveillance of the nest holes guarded by nest wardens of PanayCon (formerly Philippine Endemic Species Conservation Project (PESCP)). Personal observation of the male feeding the female, colour and consistency of faeces, presence of insects’ exo/endoskeleton, presence of some fruits under and inside the nest hole, and collection of feathers, were indicators for the presence of particular species. Species identification of the breeding pairs, which could not be observed directly, was made by genetic analysis of feather samples collected after fledging otherwise the breeding pairs were assigned as unknown (either) species.

Direct observations of breeding pairs were taken for feeding ecology and various behaviours during the breeding season. Observations were taken from a hide/blind constructed from tree branches and leaves placed at a reasonable distance from the nest hole. The observations were started from dawn (0515hr) to dusk (1815hr) to cover the whole activity period using a Leitz Televid 20-60X77 spotting scope.

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Materials and Methods

2.2.2 Nest site selection and nest tree characteristics

In order to understand the factors influencing hornbills in selecting the nest site, and nest tree species, various characteristics were measured at nest trees suitable for both hornbills. Name of the nest tree species and its previous status regarding occupancy by either hornbill was noted. In order to get an overall picture of hornbill habitat, the tree species in the immediate vicinity of the nest tree were noted. The geographic positions of the nest hole trees were taken with the help of a Global Positioning System, Garmin GPSMap 76Cx device. The girth at breast height (GBH) of the was taken with a measuring tape. Height of nest holes was measured with the help of a clinometer, or directly with a measuring tape where possible or estimated where other measurement methods were not possible due the location of nest holes. Nest opening orientation was taken with the help of a compass (compass direction in degrees with reference to magnetic north) and elevation with the help of GPS as well as with an altimeter. The location of the nest cavity in the tree (main stem, primary, secondary or tertiary branch) was noted. Where possible, the girth of the trunk at nest cavity, nest hole depth, height and diameter, the height and width of cavity opening were also measured. The digital camera Nikon D-60 was used for taking photographs of seeds, seedlings, birds, eggs, habitat characteristics, and evidences for habitat degradation. The Spearman correlation (rs) was used to determine a relationship between elevation above sea level, GBH, the nest hole height above ground. In order to find out if nest height and girth of nest trees were equally distributed throughout the elevation range of hornbill species, the elevation range was equally divided into 4 parts each consisting of a vertical section of 150m and checked for any difference of nest character, using the Kruskal-Wallis H test followed by a multiple comparison post-hoc Dunn’s test for unequal sample sizes (Glantz, 2005).

To determine the overlap between the nest tree species used by the two hornbills, Sörensen’s index of community similarity was used:

Is=2C/(D+T)

Where C is the number of nest tree species shared by both hornbill species, D is a number of tree species used by the Dulungan and T is the number of species used by the Tarictic.

The value of Is will be 1(0

16

Materials and Methods

2.2.3 Nest orientation

Orientation of entrances of Dulungan and Tarictic nest holes relative to magnetic north as a compass bearing (0-359o) was measured, using (magnetic) a compass. Using the direction of the nest opening taken by compass, mean direction was calculated based on a mean vector defined by a mean angle (α) and a mean length (r) (Batschelet, 1981; Zar, 1999): cos α = X / r or sin α = Y / r

With X = Σcos βi / n and Y = Σsin βi / n r = √ (X2+Y2)

Where n is the number of nest holes and β the compass direction of the nest hole opening (i,i+1,…, in).

The significance of the length of the mean vector was tested with the Rayleigh test (z) (Zar, 1999). z = R2 / n or z = nr2

Where R = nr

The differences in mean orientations (compass directions) of nest hole openings used by the two species and during two breeding seasons were statistically determined using Watson-Williams’ F-test:

(N-2) (R1+ R2- R) F= K N-R1- R2

N=n1+ n2, R is Rayleigh’s R with the data from the two samples being combined; R1 and

R2 are the values of Rayleigh’s R for the two samples considered separately. K is a factor, obtained from the table of “Correction Factor, K for the Watson and Williams Test” that corrects for bias in the F calculation (Zar, 1999).

2.2.4 Estimation of population size and breeding pair density

During the study period, a total of 19km2 area was surveyed. The suitable nest holes were searched out. A nest hole was deemed suitable if it was reported occupied during the

17

Materials and Methods previous two years. The population density was calculated simply by dividing total breeding pairs by the total area sampled for breeding pairs. Based on the suitable habitat for hornbill species (Klop et al., 2000), the estimates of breeding pair density were extrapolated to the total suitable area of the CPMR.

In order to determine the effect of elevation above sea level on the breeding pair densities, the population of each species in each section of the elevation was calculated and compared to see if the breeding pair density of the two species differs in terms of elevation above sea level. What constrains the breeding density of Dulungan and Tarictic, was checked graphically plotting breeding pair density against the elevation above sea level. To check whether the two species segregated statistically in terms of elevation, the nest hole distributions of both species, covering different levels of elevation were plotted on a map and also tested empirically using analysis of covariance (ANCOVA) (Quade, 1967; Conover & Imam, 1982).

2.2.5 Dispersion pattern

In order to determine the distribution pattern (random, aggregate or regular) of Dulungan and Tarictic, the GPS data (tracks and coordinates) of active nest holes of both hornbills taken during field work were transferred to the computer and Nearest Neighbour Distances (NDD) were calculated by measuring the distances between two nest locations with the help of GPS software MapSource, and ArcGis. The measurements represent the horizontal distances without taking altitudinal profile and resulting deviation with respect to flat land into account.

All suitable nest holes were charted on a map of the CPMR. In order to examine whether the distribution of active nest holes was governed by territoriality, the nest holes of both species were mapped and their distributions examined. To check the pattern of dispersion the more intensively searched areas occupied by Dulungan were, specifically, mapped on sample plots of 1km2 each and their distribution examined. Should they be regularly dispersed rather than stochastically or hyper-dispersed there would be a reasonable indication of territoriality i.e. avoidance of conspecifics, or of Dulungans by Tarictics or the other way round. To calculate the dispersion pattern empirically, Clark and Evans’s (1954) ratio R=rA/rE was used, where R is the measure of the degree to which the observed distribution departs from a random expectation with respect to the distance to

18

Materials and Methods nearest neighbour. rA is the mean of a series of observed distances to nearest neighbours and was calculated as rA=ΣNND/N, where ΣNND is the summation of the distances to the nearest neighbour and N is the number of measurements of distances taken in the observed population. rE is the mean distance which would be expected if the population were distributed at random and has a value equal to 1/2√d, where d is observed density expressed as the number of individuals per unit of area.

The value of R=1.0 indicates random dispersion, R>1.0 regular dispersion and R<1.0 hyperdispersed (aggregation) pattern of dispersion. The value of R ranges between R=0 (complete aggregation as all individuals occupy the same locus) to 2.1491(completely uniform pattern, giving a triangular lattice).

The significance of the departure of rA from rE was tested by using the following test of significance (Clark & Evans, 1954):

rA-rE c = σ rE

σ Where c is the standard variate of a normal curve and rE is the standard error of the mean distance to the nearest neighbour and was calculated as follows:

σ rE= 0.26136/√Nd

Where 0.26136 is a constant, and N is the number of measurements of distance to the nearest neighbour (Clark & Evans, 1954).

The c value was checked for significance using the table of the normal distribution.

A modified expression tR=(R-1)/var(R) (Peter Jr, 1985) of the above formula using variance of index (R) of aggregation of Clark and Evans gave the same results as those of the c value. tR (instead of c) values were compared for significance levels using the table of the normal distribution.

19

Materials and Methods

2.2.6 Feeding ecology

A methodology was worked out for identifying the diet of both species. The diet was inferred from the food remains, seeds and seedlings below and in front of the nest hole during and after breeding. The plant species were identified by the seeds regurgitated and/or defecated by the female and the nestlings as voided through the nest opening, the fruits occasionally dropped by the male during feeding the female, and where possible, fruits collected from the parent trees. The seeds were collected and seedlings photographed and given the local names by local experts, later on identified with the help of reference fruits collected during surveys, photographs at Research Station ‘Sibaliw’, and using the reference books (Seidenschwarz, 1994; Madulid, 2000; Madulid, 2001).

To check if the two species share food resources, a representative number of pairs of Dulungan and Tarictic nest holes closely neighbouring each other were selected, and the diet at each nest of a pair of neighbouring broods was identified. The distance between nearest neighbours was measured using ArcGIS 9.2 and Garmin MapSource software.

To evaluate intraspecific overlap and competition, nearest neighbours of the same species were selected and their diet compared. The diet of the broods of the same species should be indistinguishable if the fruits used would be superabundant. However, diets should diverge if there would be a shortage of fruits, resulting in competition for food.

In order to see if there is a relationship between nearest neighbours and food overlap, the diet overlaps were regressed against nearest neighbour distances. Spearman correlation was used to examine the relationship between two parameters, nearest neighbour distance and percentage food overlap. Only those nearest neighbours were used for analysis from where seeds and seedling were collected. Broods having a nearest neighbour where seeds and seedling were not collected were discarded.

Food similarity/niche overlap

To assess the interspecific and intraspecific diet overlap/similarity Sörensen’s index (Is) of community similarity was used.

Apart from a simple measure of overlap, niche overlap of fruit selection by two hornbills (interspecific) was also estimated by Horn’s index of overlap (Krebs, 1989):

20

Materials and Methods

Ro = -Σ(PiD+ PiT) ln(PiD + PiT) -Σ(PiD ln PiD) -Σ(PiT ln PiT) 2 ln 2

Where PiD is the proportion of a particular fruit species used by the Dulungan, and PiT is the proportion of the same fruit species used by the Tarictic.

Food diversity

To check how diverse the diet of the two species was in using fruit resources, the of the ׳was used (Ludwig & Reynolds, 1988). The value of H ׳Shannon-Wiener index H two species was computed and compared. The species having a high value was considered as a general feeder and the species with low value as a selective feeder. The index was derived using the following formula:

S (Σ(Pi ln(Pi- = ׳H i=1

Where S is the number of all fruit species delivered to the broods, Pi is the proportion (relative abundance) of a particular fruit species i in the diet (number of occurrences of i/total number of occurrences of all fruit species).

2.3.7 Statistical analysis

The data was checked for normality, using the Kolmogorov-Smirnov test. Based on the distribution of data, different statistical tests were used. Mann-Witney U test for independent samples was used to examine any difference in nest characteristics used by two species, and during two breeding seasons. Given the data distribution, Spearman rank correlation coefficient (rs) and simple linear regression analyses were used to determine the strength and association of various characteristic parameters. The analyses were conducted using MS Excel, SPSS, GraphPad Prism version 5.04 for windows (La Jolla California USA. www.graphpad.com), and Oriana 3.0 (trial version).

21

Results

Chapter 3 RESULTS

A study of two hornbill species, Dulungan and Tarictic, during the breeding seasons 2009 and 2010 was conducted in the CPMR, Philippines, to collect data on different ecological aspects. The study area is located at 11o 30.96′-11o 39.45′ N and 122o 07.04′-122o 09.30′ E, from 100m to 800m asl, comprising specifically the areas of Barangay Alegre and Igpatuyao of the Municipality of Sebaste, and Barangay Calabanog of the Municipality of Pandan (Fig. 2.1 and Fig. 3.2).

3.1 Status and characteristics of nest hole trees

A total of 157 suitable nest hole trees were explored within the area of 19km2 during the breeding seasons 2009 and 2010 in both municipalities. In the breeding season 2009, a total of 100 suitable nest hole trees (only those nest holes were considered suitable which were occupied in 2009 or reported being occupied previously in 2008, the empty nest holes without any previous records, were not included because of their probable unsuitability as nest holes) within an area of about 15km2 was explored for the breeding activities of both species. Out of these 100 nest trees, 54 were occupied by Dulungan, 24 holes by Tarictic (one tree contained two nest holes), and one other nest hole was occupied by Tarictic following fledging of Dulungan in the same hole and a rest (n=24) remained un-attempted during the breeding season 2009 (Fig. 3.1).

In the breeding season 2010, 145 suitable nest holes were explored within the area of 15km2, including all but a 4km2 area, and 12 nest holes explored during the previous breeding season. Out of 145 nest holes visited during the breeding season 2010, 67 were occupied by Dulungan and 35 by Tarictic, 19 by either hornbill species while 24 nest holes occupied previously by Dulungan remained un-attempted during this breeding season (Fig. 3.2).

22

Results

Fig. 3.1. Locations of 100 suitable nest hole trees available to hornbills during the breeding season 2009

23

Results

Fig. 3.2. Locations of 145 suitable nest hole trees available to hornbills during the breeding season 2010 3.1.1 Status of nest hole trees

During two breeding seasons, both species used a total of 43 nest tree species belonging to at least 18 families. The Dulungan and the Tarictic used 27 and 25 tree species, respectively. Both hornbill species shared 9 tree species during their two breeding seasons, wherein the Sörensen Index (Is = 2C/ (D+T) showed an overall 35 percent overlap in nest tree species (App. 2). 24

Results

In 2009, a total of 33 plant species were used by both hornbill species for breeding, the Dulungan used 23 and the Tarictic used 18 plant species, with 8 species in common (Fig.

3.3), wherein the Sörensen Index (Is = 2C/ (D+T) showed that there was a 39 percent (2*8/23+18) overlap in nest tree species.

18 16 14 Dulungan 12 10 Tarictic

8 6

Number 4 2 0 Pili Ayo Buri Toog Gogo Palad Lunok Taluto Bubog Libtog Nato Lagaci Salong Danlog Oropag Uya-oy Duguan Sibuyas Tul-ang Lanipga Tamuyo Kaluluto Lawa-an Taba-aw Tapoyay Lawihaw Malaboyo Maganhop Balakbakan Maglemboy Salin-Urang Kaluntingan Kamantugan Bagilomboy Plant species

Fig. 3.3. Nest hole trees used by two hornbill species during the breeding season 2009

During 2010 the two hornbill species used a total of 42 plant species for breeding, the Dulungan used 22 and the Tarictic used 24 plant species, while 4 nest tree species were occupied by either hornbill (Fig. 3.4). Both hornbills had 7 plant species in common wherein the Sörensen Index (Is = 2C/ (D+T) showed that there was a 30 percent overlap in nest tree species.

18 16 Dulungan 14 Tari cti c

12 Either hornbill 10

Number 8 6 4 2 0 Pili Ayo Buri Baid Toog Bugo Gogo Palad Bulog Yabot Mogis Lunok Taluto Lagasi Libtog Nato Salong Putian Danlog Oropag Uya-oy Oyakya Lawaan Sibuyas Tul-ang Lanipga Tamuyo Kaluluto Taba-aw Tapoyay Lawihaw Dural-Og Atay-atay Malaboyo Palomaria Maganhop Luwgating Balakbakan Salin-Urang Bagilomboy Kaluntingan Kamantugan Plant species Fig. 3.4. Nest hole trees used by two hornbill species during the breeding season 2010

25

Results

3.1.1.1 Status of nest hole trees of the Dulungan

During the breeding season 2009, out of 54 nests, 9% (n=5) were newly occupied by the Dulungan, while of the 67 nest holes reported occupied during breeding season 2008 by Dulungan, 4.5% (n=3) were occupied by Tarictic, 73% (n=49) by Dulungan and rest 22.4% (n=15) remained unoccupied. The nest hole trees occupied by the Dulungan belonged to 23 species with a highest percentage of Libtog (31.5%) followed by Balakbakan (14.8%) (Fig. 3.3 and App. 2).

Out of 67 nests occupied by the Dulungan during the breeding season 2010, 93% (n=62) were occupied in the previous year by the same species, 1% (n=1) by Tarictic, 6% (n=4) were newly occupied/explored. Of 100 (45 out of 54 visited during 2009, +55 reported by nest guards during surveys in 2010) nest holes occupied in the 2009 by Dulungan, 62% were re-occupied by the same species, 9% were occupied by Tarictic, 12% by either (unknown) species, and 17% remained non-occupied during the breeding season 2010.

The nest trees occupied by Dulungan during the breeding season 2010 belonged to 22 species, in which three species contributed about one half of total nest trees, with a highest percentage (24%, n=16) of Libtog followed by Balakbakan (16%, n=11) and Taba-aw (10%, n=7) (Fig. 3.4 and App. 2). Of nest holes occupied by Dulungan, 85% (n=57) were found in the main stem (including nest holes made directly by the primary nest hole excavator and naturally made, mostly due to breaking down of primary branches), 13% (n=9) in the primary branches due to breaking down of secondary branches, and 1% (n=1) in a secondary branch.

3.1.1.2 Status of nest hole trees of the Tarictic

Out of 24 nest holes occupied by the Tarictic during the breeding season 2009, 11 were reported occupied in the year 2008 by the same species, 4 by Dulungan and the rest (n=9) of the nest holes were newly (explored) occupied during the breeding season 2009. The Tarictic used 18 different plant species with the highest percentage being Toog (Fig. 3.3 and App. 2).

Of 35 nests occupied by Tarictic during the breeding season 2010, 57% (n=20) were those that were occupied during the preceding year by the same species, 9% (n=3) were newly occupied, 26% (n=9) were occupied by Dulungan and the rest 9% (n=3) belonged to the nest holes abandoned by Dulungan during the past two or more years. 26

Results

During the breeding season 2010, out of 23 (one nest hole could not be visited during 2010) nest holes occupied in the breeding season 2009 by Tarictic, 4% (n=1) were occupied by Dulungan, 87% (n=20) were re-occupied by Tarictic and 9% (n=2) remained unoccupied. The nest hole trees occupied by Tarictic belonged to 24 species, in which 6 (25%) species contributed one half of all nest hole trees, with a highest percentage of Libtog (11%, n=4) and Maganhop (11%, n=4), followed by Bagilomboy, Malabuyo, Salong and Toog (6%, n=2 each) (Fig. 3.4 and App. 2). Of nest holes occupied by Tarictic, 94% (n=33) were found in the main stem (excavated by other bird species and of the other natural origin), 3% (n=1) in primary branches and 3% (n=1) in secondary branches. The dimensions of a few accessible nest holes could be taken during the study period (Table 3.1).

Table 3.1. Measurements of nest holes occupied by hornbills Species Nest opening Nest hole Circumference at nest hole height width Depth Height Diameter (cm) (cm) (cm) (cm) (cm) Tarictic 15 7 16 100 45 165 Tarictic 11 7 28 125 91 300 Unknown 21 16 10 16 45 196 Unknown 17 12 18 38 18 127 Unknown 17 11 64 46 51 141

3.1.2 Characteristics of nest hole trees

The nest tree characteristics, especially nest height above ground, GBH, nest orientation and elevation above sea level may directly affect the population size of both hornbill species. Nest height above ground (rs=0.217, p=0.013, two-tailed, n=130) and GBH

(rs=0.171, p=0.052, two-tailed, n=130) increased with an increase in elevation above sea level. Similarly there was a positive significant correlation between nest height above ground and GBH (rs=0.440, p<0.0001, n=130) of nest trees used by both species (Fig. 3.5).

27

Results

25 700 y = 0.1648x + 149.8 y = 0.0107x + 4.6937 600 rs=0.171, p=0.052 20 rs=0.217, p=0.013

500

15 400

10 GBH 300 Nest height Nest 200 5 100 0 0 0 200 400 600 800 0 200 400 600 800 Altitude Altitude

25 y = 0.0178x + 5.8213 rs=0.440, p<0.0001 20

15

10 Nest Nest height

5

0 0 200 400 600 800

GBH

Fig. 3.5. Correlation between different characteristic parameters of nest trees used by two hornbill species during their breeding seasons

The nest hole heights above ground were non-uniformly distributed throughout the altitudinal range between 100m and 700m asl (Kruskal-Wallis test: H=13.77, p=0.003, df=3) (Fig. 3.6). Post-hoc comparison using Dunn’s test for significance, indicated that the median nest height above ground (11m, Interquartile range (IQR), 8-13) between 551- 700m asl was significantly higher than median nest heights (4.5m, (IQR),1.5-8.3) between 100-250m asl and 251-400m asl (8m, (IQR), 6-11m) (p<0.05) but was not different in nest height (11m, (IQR), 8-13.5m) between 401-550m asl (p>0.05). The median ` nest height between 401-550m asl was non-significantly higher than the median nest height between 100-250m asl (p>0.05) and between 251-400m asl (p>0.05). The nest height between 251-400m asl was non-significantly higher than the nest height between 100-250m asl (p>0.05).

28

Results

30

20

10 Nest height above ground (m) ground above height Nest

0 100-250 251-400 401-550 551-700

Elevation above sea level (m)

Fig. 3.6. Distribution of nest heights above ground with regard to elevation above sea level, used by hornbills during two breeding seasons. Boxes represent the 25th-75th percentile, the median is the central line in each box. The whiskers represent the range within 1.5 Interquartile range (IQR). Points beyond the whiskers are outliers In contrast to nest heights, GBH was uniformly distributed throughout an altitudinal range (Kruskal-Wallis test: H=3.94, p=0.268, df=3) between 100m-700m asl (Fig. 3.7). Family- wise detailed measurements of the characteristics of nest tree species used by the two hornbill species is given in App. 2.

800

700

600

500

400

300

200

100 Girth at Breast Height (GBH) (cm) (GBH) Height Breast at Girth

0 N = 4 23 60 43 100-250 251-400 401-550 551-700

Elevation above sea level (m)

Fig. 3.7. Distribution of nest tree GBH with regard to elevation above sea level, used by hornbills during the two breeding seasons

29

Results

3.1.2.1 Measurements of nest trees of Dulungan

The nest heights above ground used by Dulungan during the breeding season 2009 (Kolmogorov-Smirnov = 0.1346, p=0.016 n=54) and 2010 (Kolmogorov-Smirnov = 0.1436, p=0.002, n=67) deviated significantly from the normal distribution.

There was no significant difference in nest hole heights above ground used by Dulungan during two breeding seasons (Mann-Whitney U= 1778, p=0.869, two-tailed, n=121). The median height above ground of nest holes used during breeding seasons 2009 and 2010 were 11m (Interquartile range (IQR), 8-14, n=54), ranging from 5m to 20m and 11(9-14, n=67), ranging from 4m to 20m, respectively (Fig. 3.8 and App. 2). There was a highly significant difference in median nest hole heights above ground used by the two species during the breeding season 2009 (Mann-Whitney U= 270, p<0.0001, two-tailed, n=78) and 2010 (Mann-Whitney U= 564, p<0.0001, two-tailed, n=102) (Fig. 3.8)

30

25

20

15

10

Nest height above ground (m) height above Nest 5

0 N = 67 35 54 24 Dulungan 2010 Tarictic 2010 Dulungan 2009 Tarictic 2009

Species & year

Fig. 3.8. Nest hole height above ground used by the two hornbill species during breeding seasons 2009 and 2010. Boxes represent the 25th-75th percentile, the median is the central line in each box. The whiskers represent the range within 1.5 (IQR). Points beyond the whiskers are outliers Like nest hole height above ground, the Girth at Breast Height (GBH) used by Dulungan during the breeding season 2009 (Kolmogorov-Smirnov = 0.1978, p<0.0001 n=54) and 2010 (Kolmogorov-Smirnov = 0.1957, p<0.0001, n=67) deviated significantly from normal distribution. 30

Results

Similar to nest hole heights above ground, there was no difference in median Girth at Breast Height (GBH) of nest hole trees used by Dulungan during two breeding seasons (Mann-Whitney U= 1739, p=0.715, two-tailed, n=121). The Dulungan, during the first breeding season, used the trees with a median (IQR) GBH of 220cm (186-268, n=54), ranging from 140cm to 665cm, and during the second year they used the trees with a median (IQR) GBH of 224cm (186-280, n=67), with a wide range from 120cm to 665cm (Fig. 3.9 and App. 2).

There was a marginaly significant difference in median GBH of nest hole trees used by the two species during breeding season 2009 (Mann-Whitney U=471, p=0.055, two- tailed, n=78), however, the difference in median GBH was highly significant (Mann- Whitney U=792, p=0.007, two-tailed, n=102) during the breeding season 2010 (Fig. 3.9).

800

700

600

500

400

300

200

Girth at Breast Height (GBH) (cm) (GBH) Height Breast at Girth 100

0 N = 67 35 54 24 Dulungan 2010 Tarictic 2010 Dulungan 2009 Tarictic 2009

Species & year

Fig. 3.9. Mean Girth at Breast Height of nest hole trees used by the two hornbill species during breeding seasons 2009 and 2010

3.1.2.2 Measurements of nest trees of Tarictic

In contrast to the nest hole height above ground used by Dulungan during the two breeding seasons, the nest heights above ground used by Tarictic during the breeding season 2009 (Kolmogorov-Smirnov = 0.1372, p=0.2, n=24) and 2010 (Kolmogorov- Smirnov = 0.1413, p=0.075, n=35) were normally distributed. There was no difference in heights above ground of nest holes used by Tarictic during two breeding seasons (Mann- 31

Results

Whitney U= 390, p=0.646, two-tailed, n=59). The median height above ground of nest holes used during breeding seasons 2009 and 2010 were 6.5m (Interquartile range (IQR), 3-9, n=24), ranging from 1m to 14m and 7(5-9, n=35), ranging from 1m to 18m, respectively (Fig. 3.8 and App. 2).

The Girth at Breast Height (GBH) used by the Tarictic were also normally distributed during the breeding season 2009 (Kolmogorov-Smirnov = 0.0928, p<0.2 n=24) and 2010 (Kolmogorov-Smirnov = 0.1096, p<0.2, n=35). There was no difference in GBH of nest trees used by Tarictic during two breeding seasons (Mann-Whitney U= 409, p=0.871, two-tailed, n=59). The Tarictic, during the first breeding season, used the trees with a median (IQR) GBH of 196cm (141-242, n=24), ranging from 96cm to 323cm, and during the second year they used the trees with a median (IQR) GBH of 195cm (162-226, n=35), with a wide range from 96cm to 323cm (Fig. 3.9 and App. 2).

3.1.3 Orientation of the entrance of the nest hole

3.1.3.1 Orientation of the entrance of the Dulungan nest holes

There was no difference in mean orientations (compass directions) of nest holes used by

Dulungans during two breeding seasons (F1, 119 =0.067, p=0.796, Watson-Williams F-test, two-tailed). The nest hole openings during the breeding season 2009 were oriented in all directions with a high percentage facing east followed by south and north (Fig. 3.10).

40 Dulungan 2009 Tarictic 2009 35 Dulungan 2010 30

25

20

15

10 Percentage nest holes of Percentage 5

0 North East South West Orientation Fig. 3.10. Orientation of entrance of nest holes occupied by the two hornbill species during the breeding seasons 2009 and 2010

32

Results

The nest hole entrances during the breeding season 2009 were evenly distributed in all directions (n=54, z=1.07, p=n.s., Rayleigh’s test) with the mean compass direction of entrance of 113o±113 (mean±SD) (Fig. 3.11 and App. 3).

As in the first breeding season, the nest hole openings, during 2010 were also oriented in all directions (Fig. 3.10). The nest hole entrances were evenly distributed in all directions (n=67, z=0.134, p=n.s, Rayleigh’s test) with the mean compass direction of entrance of 105o ±143o (mean±SD) (Fig. 3.11 and App. 3).

Fig. 3.11. The distribution and mean compass direction of entrance of nest holes occupied by the Dulungan during the breeding seasons 2009 (left) and 2010 (right)

3.1.3.2 Orientation of the entrance of the Tarictic nest holes

There was no difference in mean orientations of nest holes used by Tarictics during two breeding seasons (F1,57 = 2.18, p=0.145, Watson-Williams F-test). Similar to the Dulungan, in the breeding season 2009 Tarictics also used the nest hole openings oriented in all directions with the highest percentage (33%) in the south direction, followed by north (Fig. 3.10). The nest hole entrances were evenly distributed in all directions (n=24, z=0.025 p=n.s, Rayleigh’s test) with a mean compass direction of entrance of 113o ±150o (mean±SD) (Fig. 3.12 and App. 4). There was no difference between the mean orientations of nest hole entrances of Dulungan and Tarictic hornbills (F1, 76 = 0.0046, p=0.995, Watson-Williams F-test) during the breeding season 2009.

33

Results

Fig. 3.12. The distribution and mean compass direction of entrance of nest holes occupied by the Tarictic during the breeding seasons 2009 (left) and 2010 (right)

The nest hole openings during the breeding season 2010 were also oriented in all directions (Fig. 3.10), and evenly distributed (n=35, z=0.702, p=n.s, Rayleigh’s test) with mean compass direction of entrance of 24o ±113o (mean±SD) (Fig. 3.12 and App. 4).

In contrast to the breeding season 2009, the mean orientation of nest entrances used by the two species during breeding season 2010, were significantly different (F1,100=6.44, p=0.013, Watson-Williams F-test).

3.2 Dispersion pattern

In order to calculate the dispersion pattern (Clark and Evans 1954), the ratio R=rA/rE of the mean of the nearest neighbour distances observed (rA=NND/n) and expected (rE=1/2 √d [d=density] was computed. A value of R=1.0 indicates random dispersion, R>1.0 regular dispersion and R<1.0 an aggregation pattern of dispersion.

3.2.1 Dispersion pattern of the Dulungan

The mean nearest neighbour distances observed for the Dulungan during the breeding season 2009 was 221±219m (mean±SD, n=54) ranging from 11m to1213m. The mean expected nearest neighbour distance if the population were distributed at random was 34

Results calculated to be 264m with standard error of the mean m±0.019. The value R=0.839 of the Clark and Evans test indicates a significant deviation (c=2.268, p<0.05, two-tailed, n=54) from randomness in the direction of aggregation pattern of dispersion for the Dulungans.

The more Dulungan rich new areas and new nest holes added in the (previously surveyed) study area during the second breeding season resulted in an increased population density, decreased distances between neighbours and a more deviation from randomness toward aggregation. The mean nearest neighbour distance decreased from 221m in 2009 to 178±165m (mean±SD, n=67) in the breeding season 2010, ranging from 18m to 882m. If the population were distributed at random the mean expected nearest neighbour distance was calculated to be 237m with standard error of the mean m±0.004. The value R=0.752 of the Clark and Evans test indicates a more significant deviation (c=3.878, p<0.001, two- tailed, n=67) than the previous year from randomness in the direction of breeding in aggregation.

The above results showing aggregation were calculated for the whole study area; the results could be more in favour of aggregation if the dispersion pattern was calculated on a local level within the 1km2 sample plots with a maximum number of nest holes occupied by Dulungan. A visual examination of some selected sample plots also reveals that the Dulungan tends to aggregate during the breeding season (Fig. 3.13).

3.2.2 Dispersion pattern of the Tarictic

During the breeding season 2009 the mean observed nearest neighbour distance for the Tarictic was 293±384m (mean±SD, n=24), ranging from 0.5m (both nest holes were present in the same tree) to 1399m. The mean expected nearest neighbour distance was 231m with standard error ±0.026. The value (R=1.268) of the Clark and Evans test showed a significant deviation (c=2.40, p<0.05, two-tailed, n=24) from randomness in the direction of regular dispersion for Tarictics.

Finding additional nest holes during the second season also affected various parameters of dispersion of the Tarictic hornbill. The mean observed nearest neighbour distance during the breeding season 2010 was calculated to be 225±210 (mean±SD, n=35), ranging from 18m to 749m. The mean expected nearest neighbour distance was 207m

35

Results

Fig. 3.13. 1-km2 sample plots (selected from the area having maximum nest holes) showing the distribution pattern of nest holes occupied by the Dulungan during the 2010 breeding season with standard error ±0.018. The value R=1.086 of the Clark and Evans test showed a non- significant negligible deviation (c=0.983, p>0.05, two-tailed, n=35) from randomness toward a regular dispersion. This difference in the dispersion pattern from the previous breeding season was due to a relatively smaller mean observed nearest neighbour distance. If more and more Tarictic nests are found in the area with the tendency of deviation from randomness toward regular dispersion may be reversed in the direction of aggregation and may thus follow the dispersion pattern of the Dulungan.

36

Results

3.3 Population density

The total density of suitable nest hole trees (including nest holes occupied by both species plus the suitable nest holes that remained un-attempted during the breeding seasons) in the area of about 19km2 surveyed during the two breeding seasons was calculated to be 8.27/km2. The density of suitable nest hole trees available to both hornbill species during the breeding seasons 2009 and 2010 was 6.67/km2and 9.7/km2 respectively.

During the breeding season 2009 an overall breeding pair density for both hornbill species together was 5.2 pairs/km2, Dulungan with 3.6 pairs/km2 and Tarictic with 1.6/km2 (when the total area surveyed for Dulungan was considered for estimation). Extrapolating from this density to the total suitable habitat (400km2) of the CPMR will give a total population of 1440 breeding pairs of the Dulungan. Based on the surveys exclusively conducted for searching for Tarictics over 4.7km2, their density was calculated to be 4.68 pairs/km2, which gives a total estimate of 1872 breeding pairs of the Tarictic in the CPMR.

In order to augment the data, during the breeding season 2010 the more Dulungan rich areas were scrutinized for more nest holes that were then added to the previously surveyed area thus yielding different population estimates (as compared to those of the previous breeding season). During the second breeding season, based on the total area surveyed, the breeding pair density for Dulungan and Tarictic was calculated as 4.47/km2 and 2.33/km2 respectively, however when the area exclusively surveyed for Tarictics was considered for density calculation, the Tarictic population density was estimated to be 5.83/km2.

Extrapolation of this density to the total suitable habitat will give a total population of 1787 breeding pairs of Dulungan and 2333 breeding pairs of Tarictic hornbill in the CPMR. The estimates can be biased towards Tarictic and may underestimate its population density as the area was not searched exclusively and intensively for Tarictic population, while on the other hand the Dulungan nest holes have thoroughly been searched and guarded for many years under the Dulungan nest guarding scheme. In addition, during the survey the Tarictics were more frequently encountered than were Dulungans, and unlike Dulungan, Tarictics do not need contiguous forests as they were found even in isolated trees out of forests and near human habitation.

37

Results

3.3.1 Population dependence on elevation

The altitudinal change above sea level can affect the composition and characteristics of forest floral community, and climatic condition, which in turn directly influence faunal community supported by these forests. The hornbills, which need forest trees for their food and nest tree with reasonable sizes and holes for breeding can directly be affected by altitudinal variation. The data were analyzed to evaluate the relationship between the two variables, elevation and breeding population density.

3.3.1.1 Population dependence of the Dulungan

During the 2009 breeding season, Dulungan were recorded between 280m and 690m asl, wherein the number of breeding pairs gradually increased with elevation up to a certain level above which the population showed a sharp decline (Fig. 3.14). About two thirds (72%, n=39) of the breeding population of the Dulungan were confined to areas between 451m and 600m asl, of which 44% (n=17) were concentrated within a range of 50m of elevation between 551m and 600m asl (Fig. 3.14). There was a positive relationship between elevation and the number of breeding pairs of the Dulungan during the breeding season 2009 (Fig. 3.15).

18 16 Dulungan Tarictic 14 Dulungan 12 Tarictic 10 8 6 4 Number of breeding pairs of breeding Number 2 0 101-150 151-200 201-250 251-300 301-350 351-400 401-450 451-500 501-550 551-600 601-650 651-700 Elevation above sea level (meter)

Fig. 3.14. Population numbers of the two hornbill species at various levels of elevation during the breeding season 2009

38

Results

18 16 y = 0.015x - 1.1325

14 12 10 8 6 4

Number of pairs of breeding Number 2 0 0 200 400 600 800

Elevation above sea level (meter)

Fig. 3.15. Breeding pair density of the Dulungan dependent on elevation during the breeding season 2009 In the breeding season 2010 the population size of Dulungan was recorded between 310m and 800m asl (above sea level), wherein the number of breeding pairs gradually increased up to an elevation, above which the population showed a declining trend. About 61% (n=41) of the breeding population of the Dulungan was confined to areas between 451m and 600m asl (Fig. 3.16). In the breeding season 2010 there was a rather weak positive relationship between elevation and number of breeding pairs of the Dulungan (Fig. 3.17).

20 18

16 Dulungan 14 Tarictic 12 Dulungan Tarictic 10 8 6 4

Number pairs breeding of Number 2 0 100-150 151-200 201-250 251-300 301-350 351-400 401-450 451-500 501-550 551-600 601-650 651-700 701-750 751-800

Elevation above sea level (meter)

Fig. 3.16. Population numbers of the two hornbill species at various levels of elevation during the breeding season 2010

39

Results

20 18 y = 0.01x + 3.245 16 14 12 10 8 6 4 Number pairs of breeding Number 2 0 0 200 400 600 800 Elevation above sea level (meter) Fig. 3.17. Breeding pair density of the Dulungan dependent on elevation during the breeding season 2010

3.3.1.2 Population dependence of the Tarictic

The Tarictic population, in 2009 breeding season, was found at an altitude of as low as 100m up to the elevation of 610m asl. The population followed almost the same trend as that of the Dulungan of increasing density with elevation up to a certain elevation level after which it declined. About 50% (n=12) of the breeding population of the Tarictic was confined between 401m and 550m asl, of which 50% (n=6) were concentrated within a range of 50m of elevation between 501m and 550m asl (Fig. 3.14). There was a rather weak positive relationship between elevation and the number of breeding pairs of the Tarictic during the breeding season 2009 (Fig. 3.18).

7

6 y = 0.0033x + 0.9529

5

4

3

2

1

Number of breeding pairs breedingNumberof 0 0 100 200 300 400 500 600 700

Elevation above sea level (meter) Fig. 3.18. Breeding pair density of the Tarictic dependent on elevation during the breeding season 2009

40

Results

A one-way Analysis of Covariance (ANCOVA), following Quade (1967), was conducted to see if populations of two hornbill species differ with respect to change in elevation above sea level. During the 2009 breeding season, ANCOVA did not show any evidence of difference in populations of the two species while controlling for elevation above sea level (F1,18 = 0.322, p=0.577).

An overall test of coincidence (Glantz, 2005), analysing the difference in slope and intercept of two regression lines, also indicated a similar trend of no difference (the two species do not exhibit different lines of means) between the regression lines of the two species (F1,16=1.784, p>0.05), since the variation about the regression lines fitted separately (Fig. 3.15 and Fig. 3.18) was approximately the same as the variation when the data of the two species were fitted together (Fig. 3.19). The effect of elevation was similar on the numbers of breeding pairs of two hornbill species during the breeding season 2009.

18

16 y = 0.0106x - 0.5664 rs=0.45, p=0.046 14 12 Tarictic 10 Dulungan 8 6

Number of Numberof breedingpairs 4 2 0 0 200 400 600 800 Elevation above sea level (meter) Fig. 3.19. Mean regression line between elevation and number of breeding pairs of the two hornbill species during the breeding season 2009 During the breeding season 2010 the population was found at an altitude of as low as 100m up to the elevation of 600m asl. The population followed almost the same trend as that of the Dulungan of increasing density with elevation up to a certain elevation level, after which it declined. About one half (51%, n=18) of the breeding population of Tarictic was confined to between 401m and 600m asl, of which 50% (n=9) were concentrated within a range of 50m of elevation between 501m and 550m asl (Fig. 3.16). There was a positive relationship between elevation and the number of breeding pairs of Tarictic (Fig. 3.20).

41

Results

10 9 y = 0.0098x + 0.0587 8 7 6 5 4 3

Number of breeding pairs breeding of Number 2 1 0 0 100 200 300 400 500 600 700 Elevation above sea level

Fig. 3.20. Breeding pair density of the Tarictic dependent on elevation during the breeding season 2010

An overall test of coincidence also indicated that there was no difference between the regression lines of the two species (F1,14=1.62, p>0.05) (Fig. 3.17, Fig. 3.20 and Fig. 3.21).

Similar to the 2009 breeding season, a one-way Analysis of Covariance (ANCOVA), conducted during 2010 also did not show any evidence of a difference in populations of the two species while controlling for elevation above sea level (F1,16 = 1.91, p=0.186).

20 18 y = 0.0152x - 0.7204 r = 0.583, p=0.011 16 s 14 Tarictic Dulungan 12 10 8 6 4 Number of breeding pairs Number 2 0 0 200 400 600 800 Elevation above sea level

Fig. 3.21. Mean regression line between elevation and number of breeding pairs of the two hornbills during the breeding season 2010

42

Results

The number of breeding pairs regressed on elevations above sea level may not be used to predict the number of breeding pairs on different elevation levels as the increasing trend in population goes to a limited elevation and dramatically decreases after a certain elevation level (Fig. 3.14 and Fig. 3.16), certainly due to the harsh condition related to changes in elevation. Unlike Tarictic breeding pairs found as low as 100m, the population of the Dulungan starts above 300m. Conversely, the Tarictic population does not go beyond 600m asl.

The results of the regression analyses might be different if the number of breeding pairs is regressed against the whole range of elevation from 100m to 800m for both species. If the elevation below 300m is included for Dulungan (the slope will get steeper) and above 600m for Tarictic (the slope will get shallower), the results might be quite different.

An inspection of a boxplot (Fig. 3.22) and a distribution map (Fig. 3.23) of both species together also give an expression of two species possessing different elevation ranges above sea level. The median elevation above sea level of nest trees used by the Dulungan and the Tarictic during the breeding seasons 2009 were 535m (Interquartile range (IQR), 470-590, n=54), ranging from 280m to 690m, and 450(303-531, n=24), ranging from 100m to 610m, respectively.

During the 2010 breeding season the median elevation above sea level of nest trees used by Dulungan and Tarictic were 530m (IQR), 470-600, n=67), ranging from 310m to 780m and 410m (310-540, n=35), ranging from 100m to 600m, respectively. Both species differed significantly in their distribution of nest holes above sea level during the breeding season 2009 (Mann-Whitney U=336, p=0.001, two-tailed, n=78) and 2010 (Mann-Whitney U=593, p<0.0001, two-tailed, n=102). However, there was no difference in nest distribution above sea level used by Dulungan (Mann-Whitney U=1743, p=0.732, two-tailed, n=121) and Tarictic (Mann-Whitney U=417, p=0.963, two-tailed, n=59) between two breeding seasons.

43

Results

1000

800

600

400

Elevation above sea level sea above Elevation 200

0 N = 67 35 54 24 Dulungan 2010 Tarictic 2010 Dulungan 2009 Tarictic 2009

Species

Fig. 3.22. Distribution of active nest holes of the two hornbills with regard to elevation range during two breeding seasons

Fig. 3.23. Location and distribution of Dulungan and Tarictic occupying different levels of elevation above sea level

44

Results

3.4 Food and feeding ecology

A total of 157 suitable nest hole trees of two hornbill species were explored during two breeding seasons, 100 in the 2009 breeding season and 145 in the 2010 breeding season. Out of the former 100 nest hole trees, 54 were occupied by the Dulungan, 24 by the Tarictic, while out of the later 145 nest hole trees, 67 belonged to the Dulungan and 35 to the Tarictic, while 19 were occupied by either (unknown) species.

During the two breeding seasons, the seeds were collected from 135 nest holes occupied by the two species. During the 2009 breeding season, the seeds were collected from 25 Dulungan and 18 Tarictic nests. During the 2010 breeding season seeds were collected from 59 Dulungan, 17 Tarictic and 16 either (unknown) hornbill broods.

3.4.1 Fruit species consumed during the breeding seasons 2009-10

The average number of fruit species (seeds regurgitated by female and nestlings, fruits fallen during feeding by male, and seedlings germinated under nest holes) collected under/inside nest holes of both species during the two breeding seasons was 6.2±3.2 (mean±SD, n=135) ranging from 1-17 species. The average number of fruit species collected from nest hole was 6.1±3.6 (mean±SD, n=25), ranging from 2 to 16 species for Dulungan, and 5.33±3.27 (mean±SD, n=18) ranging from 2-13 for Tarictic breeding pairs during the first breeding season. During the second breeding season, the average number of fruit species collected from nest hole was 7.19±3.2 (mean±SD, n=59) ranging from 2- 17 and 5.29±2.39 (mean±SD, n=17) ranging from 1-9 species, respectively, for Dulungan and Tarictic.

The fruit remnants collected during two breeding seasons belonged to about 24 families, 31 genera and 52 species. The most common species belonged to families Myristicaceae (5 species), Myrtaceae (3), Palmae (3), Meliaceae (3), and Moraceae (2), (Table 3.2).

During the 2009 breeding season, the fruits, seeds and seedlings of 41 tree species belonging to 27 genera and 23 families were collected from the nest holes of both hornbill species (Table 3.2 and Fig. 3.24). Dulungan used 34 species and Tarictic used 33 fruit species, both had 26 fruit species in common (78 percent).

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Results

Table 3.2. Fruit species delivered by Dulungan and Tarictic males to the breeding females and broods during two breeding seasons (X=Present) Breeding year 2009 Breeding year 2010 Local name Scientific name Family Dulungan Tarictic Dulungan Tarictic Alibotra Arcangelisia flava Menispermaceae X X X X Amogis Koordersiodendron pinnatum Anacardiaceae X X - - Anta-ata - - X - Apoy Pinanga sp. Palmae X X X X Baid X - X - Bakan Platea excelas Icacinaceae X X X X Bangkagan Leea manillensis Vitaceae X X X - Banilad Sterculia philippinensis Sterculiaceae - X X - Batikolin nato X - X - Batikulin Areca catechu Palmae X X X - Biri sp. Moraceae - - X X Bugohansol Prunus fragrans Rosaceae X X X X Bulog Azidaracha indica Meliaceae X X X - Dalakit Ficus sp. Moraceae - - X - Duguay-1 Myristica philippensis Myristicaceae X X X X Duguay-2 Myristica ceylanica Myristicaceae X X X X Duguay-3 Myristica sp. Myristicaceae X X X X Gugo (Bagusalay) Ganophyllum falcatum Sapindaceae X X X X Haras Garcinia ituman Guttiferae - - X -

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Results

Breeding year 2009 Breeding year 2010 Local name Scientific name Family Dulungan Tarictic Dulungan Tarictic Indang Myristica cumingii Myristicaceae - X X - Kalumpit X - - - Kamagong (Amaga) Diospyros philippensis Ebenaceae - - X - Kaningag Litsea cumingiana Lauraceae - X X - Kinematis Myristica sp. Myristicaceae X X X X Kulyat X X X - Langi-ngi Cayratia trifolia Vitaceae - X X X Lawi-Lawi Taba-aw Syzygium whitfordii Myrtaceae - - X - Magbinlod Syzygium sp. Myrtaceae X X X X Magobatwan Garcinia lateriflora Guttiferae - - X - Magohansol Sandoricum koetjape Meliaceae X X X X Magusalong - X X - Malabuyo Alangium meyeri Alangiaceae X X X X Malig-ang Shorea sp. Dipterocarpaceae X X X X Marobo mercadoi Lauraceae - - X X Mayabason Taba-aw Syzygium zanthophyllum Myrtaceae X - X X Mogis - X X - Nato Palaquium luzoniense Sapotaceae X X X X Pasi Buchanania microphylla Anacardiaceae X X X X Pili Canarium sp. Burseraceae X X X X

47

Results

Breeding year 2009 Breeding year 2010 Local name Scientific name Family Dulungan Tarictic Dulungan Tarictic Pinay Diospyros pyrrhocarpa Ebenaceae X - X - Polyalthia sp. Polyalthia sp. Annonaceae X X X - Red nato X X X X Sarawag Pinanga insignis Palmae - - X - Saronggatay Elaeagnus latifolia Elaeagnaceae X _ X Taba-aw Aglaia sp. Meliaceae X - X - Talisay gubat Terminalia foetidissima Combretaceae X X X X Toog Bischofia javanica Euphorbiaceae X - X - Uya-oy Planchonia spectabilis Lecythidaceae X X X X White Nato Pouteria macranthum Sapotaceae X X X X Unidentified-1 - - X X Unidentified-2 - - X X Unidentified-3 - X - -

48

Results

During the 2010 breeding season both species consumed 48 fruit species, belonging to 30 genera and 24 families (Table 3.2 and Fig. 3.25). The Dulungan used 48 species while Tarictic consumed 26 with 26 fruit species common in their diet. There was 70 percent overlap in the diet of both species during the breeding season 2010. During the two breeding seasons, both species utilized 52 fruit species. Dulungan used 51 species while Tarictic used 38 fruit species. Both the hornbill species shared 37 fruit species, giving an overall diet overlap of 83 percent.

Horn’s index also indicated a high niche overlap in fruits delivered to the brood during the two breeding seasons. The niche overlaps during the breeding season 2009 and 2010 were Ro= 0.83 and Ro=0.86, respectively. Both hornbills being sympatric and using the same fruit resources and a very high niche overlap indicate that two species might get in strong competition for same fruit species during the period of shortage of these fruits.

3.4.2 Feeding ecology of the Dulungan

3.4.2.1 Food type and food diversity

During the 2009 breeding season, the seeds and seedlings were collected under 25 Dulungan nest holes. The fruit species Pili (Canarium sp.) was collected from 11% of Dulungan broods. The other species found frequently were White Nato (Pouteria macranthum, 9%), Uya-oy (Planchonia spectabilis, 8%), Bugohansol (Prunus fragrans, 6%) and Maguhansol (Sandoricum koetjape, 6%) (Fig. 3.24).

During the 2010 breeding season, the seeds and seedlings from 59 Dulungan nest holes were collected. The most frequently occurring fruit was Uya-oy (Planchonia spectabilis, 11%, n=35) followed by Maguhansol (Sandoricum koetjape), Bakan (Platea excelsa), Dugu-ay (Myristica philippensis) and Bugohansol (Prunus fragrans) (Fig. 3.25).

The fruit species delivered more frequently by the Dulungan during the two breeding seasons was Uya-oy (Planchonia spectabilis) followed by Pili (Canarium sp.) and Maguhansol (Sandoricum koetjape) (Table 3.3). However, in terms of fruit families, Meliaceae, Myristicaceae, and Lecythidaceae were more preferred families consumed by the Dulungan during the two breeding seasons (Table 3.4).

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Results

14

12

10 Dulungan Tarictic 8

6

4

2 Percent frequency of occurrence frequency Percent

0 Pili Pasi Nato Toog Baid Apoy Pinay Bulog Bakan Mogis Kulyat Indang Uya-oy Banilad Amogis Alibotra Taba-aw Red nato Red Batikulin Jackfruit Kalumpit Kaningag Langi-ngi Duguay-1 Duguay-2 Duguay-3 Malabuyo Kinematis Malig-ang Magbinlod Bangkagan Mayabason… White NatoWhite Bugohansol Magusalong Magohansol Saronggatay Talisay gubat Talisay Batikolin nato Batikolin Unidentified-3 Polyalthia spp. Polyalthia

Gugo Gugo (Bagusalay) Fruit species

Fig. 3.24. Percent frequency of occurrence of fruit species consumed by Dulungan and Tarictic during their 2009 breeding season

50

Results

12

Dulungan 10 Tarictic

8

6

4

2 Percent frequency of occurrence of occurrence frequency Percent

0 Pili Biri Pasi Baid Nato Toog Apoy Pinay Haras Bulog Bakan Mogis Kulyat Indang Dalakit Uya-oy Banilad Marobo Alibotra Anta-ata Sarawag Taba-aw Red nato Red Batikulin Kaningag Langi-ngi Duguay-1 Duguay-2 Duguay-3 Malabuyo Kinematis Malig-ang Kamagong Magbinlod Bangkagan White Nato White Bugohansol Magusalong Magohansol Magobatwan Talisay gubat Talisay Batikolin nato Batikolin Unidentified-1 Unidentified-2 Polyalthia spp. Polyalthia Gugo (Bagusalay) Gugo Lawi-Lawi Taba-aw Lawi-Lawi Mayabason Taba-aw Mayabason

Fruit species

Fig. 3.25. Percent frequency of occurrence of fruit species consumed by Dulungan and Tarictic during their 2010 breeding season

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Results

Table 3.3. Overall ranking of fruit species delivered to the brood of two hornbills during the two breeding seasons Dulungan Tarictic

Local Name Scientific Name Family Score Rank Score Rank Alibotra Arcangelisia flava Menispermaceae 8.1 8 3.2 17 Amogis Koordersiodendron Anacardiaceae 1.3 31 1.1 20 pinnatum Anta-ata - - 0.2 36 0.0 Apoy Pinanga sp. Palmae 3.4 22 4.3 15 Baid 3.4 22 0.0 Bakan Platea excelsa Icacinaceae 9.1 6 10.8 7 Bangkagan Leea manillensis Vitaceae 7.7 8 1.1 20 Banilad Sterculia philippinensis Sterculiaceae 0.5 35 3.2 17 Batikolin nato - - 1.6 28 0.0 Batikulin Areca catechu Palmae 2.3 25 2.1 19 Biri Ficus sp. Moraceae 0.2 36 1.1 20 Bugohansol Prunus fragrans Rosaceae 10.6 5 15.0 3 Bulog Azidaracha indica Meliaceae 4.3 18 2.1 19 Dalakit Ficus sp. Moraceae 0.5 35 0.0 Duguay-1 Myristica philippensis Myristicaceae 7.3 11 11.9 5 Duguay-2 Myristica ceylanica Myristicaceae 4.4 17 3.3 16 Duguay-3 Myristica sp. Myristicaceae 5.3 14 4.4 14 Gugo Ganophyllum falcatum Sapindaceae 4.4 17 6.5 11 Haras Garcinia ituman Guttiferae 0.7 34 0.0 Indang Myristica cumingii Myristicaceae 0.2 36 1.1 20 Kalumpit - - 0.7 34 0.0 Kamagong Diospyros philippensis Ebenaceae 0.9 33 0.0 Kaningag Litsea cumingiana Lauraceae 0.9 33 1.1 20 Kinematis Myristica sp. Myristicaceae 2.5 24 4.4 14 Kulyat - - 1.6 28 1.1 20 Langi-ngi Cayratia trifolia Vitaceae 1.7 27 2.2 18 Lawi-Lawi Taba-aw Syzygium whitfordii Myrtaceae 0.2 36 0.0 Magbinlod Syzygium sp. Myrtaceae 4.8 16 5.3 13 Magobatwan Garcinia lateriflora Guttiferae 0.2 36 0.0 Magohansol Sandoricum koetjape Meliaceae 12.1 3 10.9 6 Magusalong - - 0.2 36 1.1 20 Malabuyo Alangium meyeri Alangiaceae 6.4 12 7.7 10 Malig-ang Shorea sp. Dipterocarpaceae 4.9 15 6.5 11 Marobo Cinnamomum mercadoi Lauraceae 1.4 29 3.3 16 Mayabason Taba-aw Syzygium zanthophyllum Myrtaceae 3.0 23 2.2 18 Mogis - - 0.5 35 1.1 20 Nato Palaquium luzoniense Sapotaceae 7.5 10 12.8 4 Pasi Buchanania microphylla Anacardiaceae 3.5 21 9.9 8 52

Results

Dulungan Tarictic

Local Name Scientific Name Family Score Rank Score Rank Pili Canarium sp. Burseraceae 13.6 2 19.4 1 Pinay Diospyros pyrrhocarpa Ebenaceae 3.6 20 0.0 Polyalthia spp. Polyalthia sp. Annonaceae 4.2 19 1.1 20 Red nato - - 8.6 7 5.4 12 Sarawag Pinanga insignis Palmae 1.2 32 0.0 Saronggatay Elaeagnus latifolia Elaeagnaceae 0.7 34 0.0 Taba-aw Aglaia sp. Meliaceae 1.4 30 0.0 Talisay gubat Terminalia foetidissima Combretaceae 5.8 13 4.4 14 Toog Bischofia javanica Euphorbiaceae 1.4 30 0.0 Uya-oy Planchonia spectabilis Lecythidaceae 16.1 1 15.3 2 White Nato Pouteria macranthum Sapotaceae 11.4 4 9.6 9 Unidentified-1 - - 2.1 26 1.1 20 Unidentified-2 - - 1.4 29 1.1 20 Unidentified-3 - - 0.0 2.1 19

indicates that the fruits consumed by the (׳Shannon-Wiener index of food diversity (H than that used (3.53=׳Dulungan during the 2010 breeding season were more diverse (H Table 3.4). Both species had almost similar) (3.20=׳during the 2009 breeding season (H ,(3.19=׳Tarictic: H ;3.20=׳diversity indices during the breeding season 2009 (Dulungan: H however, during the 2010 breeding season the diversity index of fruits was higher for Dulungan than that of Tarictic (Table 3.4). This difference in diversity might be due to the inclusion of Dulungan rich areas that might have differed also in fruit phenology.

Table 3.4. Percent occurrence of fruit species and fruit food diversity indices for the -Shannon = ׳Dulungan and the Tarictic during the breeding seasons 2009 and 2010 (H Wiener Diversity index) Dulungan Tarictic (3.27 = ׳H) (3.54 = ׳H) Year 2009 Year 2010 Year 2009 Year 2010 No. of Fruit No. of Fruit No. of Fruit No. of Fruit Species (%) species (%) species (%) species (%) No. breeding pairs (25) (59) (18) (17) Fruit family Alangiaceae 1 5.3 1 1.2 1 2.1 1 5.6 Anacardiaceae 1 0.7 1 2.8 1 2.1 1 7.8 Anacardiaceae 1 1.3 0 0.0 1 1.1 0 0.0 Annonaceae 1 3.9 1 0.2 1 1.1 0 0 Burseraceae 1 10.5 1 3.1 1 11.6 1 7.8

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Results

Dulungan Tarictic (3.27 = ׳H) (3.54 = ׳H) Year 2009 Year 2010 Year 2009 Year 2010 No. of Fruit No. of Fruit No. of Fruit No. of Fruit Species (%) species (%) species (%) species (%) Combretaceae 1 1.3 1 4.5 1 1.1 1 3.3 Dipterocarpaceae 1 1.3 1 3.5 1 2.1 1 4.4 Ebenaceae 1 2.0 2 2.6 0 0 0 0 Elaeagnaceae 1 0.7 0 0 0 0 0 0 Euphorbiaceae 1 0.7 1 0.7 0 0 0 0 Guttiferae 0 0 2 0.9 0 0 0 0 Icacinaceae 1 4.6 1 4.5 1 5.3 1 5.6 Lauraceae 0 0 2 2.4 1 1.1 1 3.3 Lecythidaceae 1 7.9 1 8.3 1 4.2 1 11.1 Meliaceae 3 9.2 3 8.5 2 5.3 1 7.8 Menispermaceae 1 4.6 1 3.5 1 2.1 1 1.1 Moraceae 0 0 2 0.7 0 0 1 1.1 Myristicaceae 4 7.2 5 12.5 5 10.5 4 14.4 Myrtaceae 2 3.9 3 4.0 1 4.2 2 3.3 Palmae 2 2.0 3 5.0 2 4.2 1 2.2 Rosaceae 1 5.9 1 4.7 1 9.5 1 5.6 Sapindaceae 1 1.3 3 10.1 1 3.2 1 3.3 Sapotaceae 2 11.8 0 0 2 16.8 2 5.6 Sterculiaceae 0 0 1 0.5 1 3.2 0 0 Vitaceae 1 3.9 2 5.4 2 2.1 1 1.1 Other fruits 5 9.9 9 10.4 5 7.4 3 5.6 Diversity index 3.20 3.53 3.19 3.05 (׳H)

3.4.2.2 Intraspecific nearest neighbour food overlap

Out of 25 Dulungan nest holes, 13 nearest neighbouring pairs where seeds and seedling were collected, were selected for the food overlap analysis (App. 5). Only those broods, which had nearest neighbours, where seeds could be collected, were included in the nearest neighbour food overlap analysis. The mean nearest neighbour distance was 99±88m (mean±SD, n=13) ranging from 11m to 260m. The mean overlap in diet (Sörensen-Index) between nearest breeding pairs was 46±25.9% (mean±SD, n=13) ranging from 0-100%. Two variables, nearest neighbour distance and overlap of fruit 54

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species were non-significantly negatively correlated (rs= -0.532, p=0.06, two-tailed, n=13) (Fig. 3.26).

120 y = -0.1345x + 59.551 r = -0.532, p=0.06 100 s

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60

Percent food overlap food Percent 40

20

0 0 50 100 150 200 250 300 Nearest neighbour distance (m)

Fig. 3.26. Relationship between nearest neighbour distance and food overlap between breeding pairs of the Dulungan during the 2009 breeding season

Out of 59 breeding pairs of Dulungan, of which seeds were collected during the 2010 breeding season, 36 pairs of nearest broods were used to determine the food overlap between nearest breeding pairs (App. 6). The mean nearest neighbour distance and mean percent food overlap were 179±143.8m (mean±SD, n=36), ranging from 18m to 713m and 35±18% (mean±SD, n=36), ranging from 0% to 92%, respectively. The negative correlation between nearest neighbour distance and overlap of fruit species was significant (rs=-0.488, p=0.003, two-tailed, n=36) (Fig. 3.27), meaning that the overlap is decreasing with distance.

Being the members of the same species, and having the same food requirements, in fact two neighbouring broods should have 100 percent similarity in their food. The difference in the fruit consumption, especially for the nearest brood having no overlap in their diet might be an indication of fruit shortage and partitioning of resources to reduce drastic effects of intra specific competition.

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100 y = -0.061x + 45.847 90 rs=-0.488, p=0.003

80 70 60 50 40 30 Percent Percent overlap food 20 10 0 0 200 400 600 800

Nearest neighbour distance (m) Fig. 3.27. Relationship between nearest neighbour distance and food overlap between breeding pairs of the Dulungan during the 2010 breeding season

3.4.3 Feeding ecology of the Tarictic

3.4.3.1 Food type and food diversity

During the 2009 breeding season, the seeds were collected from a total of 17 breeding pairs of Tarictics. Like Dulungan, Tarictic also used fruit species Pili (Canarium sp.) more frequently (11% of brood). Other fruit species consumed were Nato (Palaquium luzoniense), Bugohansol (Prunus fragrans), White Nato (Pouteria macranthum) (Fig. 3.24). During the 2010 breeding season, seeds were collected from 17 Tarictic nest holes. Fruit species Uya-oy (Planchonia spectabilis) was collected from 9% of Tarictic broods. Pili (Canarium sp.), Pasi (Buchanania microphylla) and Magohansol (Sandoricum koetjape) were collected from 8% of nest holes (Fig. 3.25).

Fruit data, pooled for two breeding seasons, show that fruit species consumed more frequently by the Tarictic, were Pili (Canarium sp.), Uya-oy (Planchonia spectabilis) and Bugohansol (Prunus fragrans) (Table 3.3). The most preferred fruit families consumed by the Tarictic during both seasons belonged to Sapotaceae, Myristicaceae and Burseraceae (Table 3.4).

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indicates that the (׳Unlike Dulungan, the Shannon-Wiener index of food diversity (H fruits consumed by the Tarictic during the 2010 breeding season were relatively less .(breeding season (Table 3.4 (3.19 = ׳than that used during 2009 (H (3.05 = ׳diverse (H

An overall Shannon-Wiener index of food diversity indicates the degree of difference in fruit consumption by both species during two breeding seasons. The diversity index = ׳indicates that the Dulungan is more of a generalist with regard to fruit consumption (H Table 3.4). The Dulungan depends almost solely on fruits) (3.27 = ׳than Tarictic (H (3.54 during the breeding season in contrast to Tarictic that supplements its diet with animal food as indicated by the presence of exoskeletons of insects in the faeces under the nest holes and during the direct observation of a Tarictic brood (App. 11), and the Dulungan also used more fruit species than the Tarictic.

3.4.3.2 Intraspecific nearest neighbour food overlap

Out of 18 only 8 pairs of nearest broods, where seeds and seedlings were collected, were used to determine the overlap between nearest breeding pairs (App. 7) during the 2009 breeding season. The mean nearest neighbour distance was 116±155m (mean±SD, n=8). The mean overlap in diet between nearest breeding pairs was 42±27.5% (mean±SD, n=8). The correlation between nearest neighbour distance and overlap of fruit species was non- significantly negatively correlated (rs=-0.467, p=0.243, two-tailed, n=8).

During the 2010 breeding season, of 17 breeding pairs of Tarictics, 5 pairs of nearest neighbouring broods were used to determine the overlap between nearest breeding pairs (App. 8). The mean nearest neighbour distance was 212±204m (mean±SD and the mean overlap in diet between nearest breeding pairs was 48±9.2% (mean±SD, n=5), ranging from 36 to 57%. The correlation between nearest neighbour distance and overlap of fruit species was non-significantly negatively correlated (rs=-0.6, p=0.285, two-tailed, n=5). Due to insufficient data for regression analysis, the food data of two breeding seasons were pooled to determine if the food overlap was a function of distance between nearest breeding pairs. The correlation between nearest neighbour distance and food overlap of pooled data for both breeding seasons of Tarictic was also non-significantly negatively correlated (rs=-0.339, p=0.257, two-tailed, n=13) (Fig. 3.28).

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120 y = -0.0358x + 49.716 100 rs=-0.339, p=0.257

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60

40 Percent food overlap food Percent 20

0 0 100 200 300 400 500 600 Nearest neighbour distance (m) Fig. 3.28. Relationship between nearest neighbour distance and food overlap between breeding pairs of the Tarictic during the breeding seasons 2009 and 2010 3.4.4 Interspecific nearest neighbour food overlap

During the 2009 breeding season, nine Tarictic breeding pairs close to Dulungan breeding pairs were selected for food overlap analysis (App. 9). The mean nearest neighbour distance was 410±436m (mean±SD, n=9), ranging from 36m to 1447m. The mean overlap in diet between nearest breeding pairs was 26±21.6% (mean±SD, n=9) ranging from 0-60%. The correlation between nearest neighbour distance and overlap of fruit species was non-significantly negatively correlated (rs= -0.511, p=0.16, two-tailed, n=9) (Fig. 3.29).

70 y = -0.0044x + 27.325 60 rs= -0.511, p=0.16

50

40

30

20

10 Percent food overlap food Percent 0 0 500 1000 1500 2000 Nearest neighbour distance (m)

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Fig. 3.29. Relationship between nearest neighbour distance and food overlap between breeding pairs of the Dulungan and Tarictic during the 2009 breeding season In the 2010 breeding season analysis of food overlap of 15 Tarictic breeding pairs neighbouring Dulungan broods was made (App. 10). The mean nearest neighbour distance and mean percent food overlap between the breeding pairs of two species were 392±437m (mean±SD, n=15) ranging from 19m to 1486m and 14±13.4% (mean±SD, n=15) ranging from 0% to 36%, respectively. The correlation between nearest neighbour distance and overlap of fruit species was non-significant negatively correlated (rs=-0.104, p=0.713, two-tailed, n=15) (Fig. 3.30).

In contrast to intraspecific nearest neighbour diet overlap, interspecific overlap between Tarictic and Dulungan is very low, and the same is true for the correlation between nearest neighbour distance and food overlap. This might indicate a shift in food consumption to avoid competition for food between two species. In contrast to intraspecific nearest neighbour food overlap, interspecific food overlap between two neighbouring broods did not exceed 60 percent.

40

35 y = -0.0086x + 17.447 rs=-0.104, p=0.713

30

25

20

15

Percent food overlap food Percent 10

5

0 0 200 400 600 800 1000 1200 1400 1600 Nearest neighbour distance (m)

Fig. 3.30. Relationship between nearest neighbour distance and food overlap between breeding pairs of the Dulungan and Tarictic during the 2010 breeding season

During fieldwork, members of both hornbill species were encountered while flying to, perching in and feeding in fruiting trees. The Tarictics were observed and heard more frequently than Dulungans. The maximum number of Dulungans observed during surveys was a group of six males and four females flying and calling above the canopy and also found on a Dalakit tree (Ficus sp.). However, during the whole study period, never were 59

Results both hornbill species seen together on fruiting trees or otherwise. This might indicate the avoidance of two species of possible encounters and existence of resource partitioning in terms of fruit consumption and/or timing.

3.5 Breeding biology

3.5.1 Breeding biology of the Dulungan

The data collected during the breeding season indicated that the breeding season of Dulungan started usually in early March and ended in July. The fledging of Dulungan started mostly in late June and early July. However, some of the nest holes were found fledged already in the end of May, indicating that the sealing of the nest hole in some areas might have started in the end of February. This timing of breeding might vary in different areas and in different years. The male and female were found in courtship even at the end of March, while very few nest holes were still sealed in the last week of July. However, no breeding activity/ nest hole was found sealed/active in August.

Before the start of breeding, the male and female were found in fruiting trees having beak to beak contact with the male offering fruits to a female (Plate 3.1).

Plate 3.1. A breeding pair of Dulungan in a fruiting tree, having beak to beak contact, the male offering fruit to the female before nest hole sealing 60

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After pair formation and selection of a nest hole site, the female started cleaning the nesthole (Plate 3.2). During the cleaning process the female was provided fruits by the male, as indicated by some fresh figs and faeces found under the nest hole. Some fruits, besides used as food by the female, were also used for nest hole sealing.

Plate 3.2. Dulungan female exiting opening after cleaning nest hole The nest hole is sealed by the female until a narrow slit (Plate 3.3) is left for receiving food from the male during the whole period of incarceration. After completion of sealing, the female lays about 3 eggs (Plate 3.4).

Plate 3.3. Sealed nest holes occupied by the Dulungans 61

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Plate 3.4. A sealed nest hole occupied by the Dulungan, containing 3 eggs

3.5.2 Breeding biology of the Tarictic

The breeding season of the Tarictic started in mid-March and ended in the end of July. A nest hole in the Malumpati area, containing three eggs, was reported occupied on 20 March, one of the brood in the Calabanog area fledged on 15 June and another completed its fledging on 18 June. The female leaves the nest hole at least 5 days before the last chick fledges as inferred from fledging of a Tarictic brood (App. 11). Backdating of fledging of Tarictic also supports starting of breeding some way in the middle of March.

All the breeding pairs of Tarictics for which direct observations during the breeding season were made, belonged to the Dulungan free areas where they had no direct competition for resources with Dulungans. In the areas where both species shared resources, the competition for the nest hole might have forced the Tarictic to defer the breeding until nest holes suitable for the Dulungan were fully occupied. Depending on the availability of nest holes the delay was prolonged even farther for more than a month until the availability of nest holes after fledging of the Dulungan brood as witnessed in the area of Catmon, where a breeding pair of Tarictic occupied the nest hole soon after fledging of the Dulungan brood. Such a situation of taking over nest holes by the Tarictic 62

Results after completion of breeding by the Dulungan clearly indicates shortage of suitable nest holes and consequent competition over nest holes between the two sympatric hornbill species.

However, in order to mitigate the competition for nest holes Tarictic might use a nest unsuitable for Dulungan. In the Malumpati area, the Tarictic had laid three eggs in unsealed opening concealed by adventitious roots and branches (Plate 3.5). This is a unique behaviour, since it is not mentioned in the literature that the Tarictic female lays eggs/breeds in open/unsealed hole. In addition, a Tarictic breeding pair was reported to have occupied a hole in a rock crevice in the Malumpati area.

Plate 3.5. Nest tree with an unsealed nest hole shielded by adventitious roots and ferns 3.5.3 Moulting of feathers of the breeding female

The breeding female moults her flight (and tail) feathers during the period of incarceration in the nest hole. Recovery of very few or no feather inside/outside nest holes (Plate 3.6) leaves open the possibility that most shed feathers inside the holes undergo rapid decomposition, and the feathers thrown out of the nest hole can have different fates. They can be dispersed from the nest tree by heavy wind, they can be carried away by heavy rain/flooding, and/or can undergo decomposition rapidly due to hot and humid climatic conditions. The assumption of decomposition within the nest hole was verified by taking the whole trash from the nest hole for examination. It could be inferred from black powdered material recovered from some of the nest holes that it might be the end product of decomposed material including shed feathers. The same is 63

Results true for the seeds as observed during the survey that many seeds, especially with soft testas, underwent decomposition.

Plate 3.6. Tree climber taking nest measurements and collecting feathers of hornbill

3.5.4 Behavioural observations during the breeding season

Opportunistic data obtained during field surveys and direct observations on feeding and breeding of two hornbill species during the different stages (incubation, nestling and fledging) of the breeding cycle revealed various aspects of behaviour.

3.5.4.1 Vigilance and nest concealment behaviour of hornbills

During the survey of nest hole trees the males of both species were usually found vigilant, remaining silent and thus probably concealing themselves and inmates. While feeding the inmate, both species did not visit the hole directly. The males would first perch on a nearby branch of distant trees, scan the area for possible threats and then approach the nest hole silently or give a soft call. On many instances, the Dulungans heading to the nest trees for feeding breeding-females and broods, on anticipating disturbance, instead of

64

Results approaching the nest holes, diverted their flights back. However, on disturbance, the male utters loud alarm calls probably alerting his mate to danger. During the survey one of the sealed Dulungan females, on disturbance, uttered repeated loud calls in the cavity, while in response to her call one female and three males were found flying restlessly around, giving loud alarm calls. The nest hole was climbed and checked for its status. It contained three eggs of normal size (of hen eggs) (Plate 3.4). Surprisingly, the female after hearing alarm calls from her mate outside, disappeared from inside the nest hole, certainly climbed up the funk tree cavity above the nest hole that allowed us to check the nest hole and take photographs of the eggs. The sealing material was very sticky, containing seeds of figs, decayed wood, probably fruit pulp and faecal material.

3.5.4.2 Acclimation of hornbills to change of habitat

The problems encountered during taking direct observation of a hornbill brood for a long period is to habituate the bird successfully to the (new) changes in its habitat.

The bird being very wary and vigilant (Plate 3.7), avoids visiting the nest hole on disturbance, probably in order to not give away its brood. It turns to its nest hole after scanning the environs for any disturbance and danger (Plate 3.8 and Plate 3.9)

Plate 3.7. A male Tarictic observing vigilantly a newly constructed hide and scanning the area

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Plate 3.8. Male (left) and female while visiting nest hole are scanning the nest environs

Plate 3.9. Female Tarictic peeping into nest hole containing three eggs

The period of acclimation varied from area to area depending on previous interactions of the birds with human related disturbances. During observation of a nest hole in Calabanog area, the male did not acclimate even after a long time of 6 days. In the Malumpati area, which is near a human habitation, and people used to work in the area, the bird acclimated within two days.

Another nest hole was observed during the fledging period in the Kabuluan area of Barangay Calabanog (App. 11). The nest tree was in the agricultural land where people used to work very often in the fields. The Tarictic male in this area, used to human activities, very quickly, within a few hours, habituated to the new structure (Plate 3.10).

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Plate 3.10. A hide constructed for (direct) observation of the Tarictic Hornbill: front (left) and from above (right) views The hornbills expressed their behaviour in response to any disturbance and change in their home range in different ways. During surveys while walking, or staying for a short time by their nest holes for taking data, they might not utter any call, probably in order to hide the broods. In response to a newly constructed blind the Tarictic responded vigorously. In a first instance, lone male gave alarm calls and later on was accompanied by a group of other Tarictics, uttering loud alarm calls above the hide (App. 11).

3.5.4.3 Food withholding and fledging

After the breeding female leaves the nest hole, the male continues to provide food to the nestlings until fledging of the last chick. During feeding, the male would approach the nest hole, uttering a short call, the nestlings would respond by screaming and begging for food. Before clinging to the nest hole the male usually regurgitated the first food item on a nearby branch (Plate 3.11).

Plate 3.11. Male Tarictic holding regurgitating fruit in bill tip (left) before clinging to the nest hole to feed the nestlings (right)

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Observations of the Tarictic brood during the fledging period revealed that the male very often visited the nest without food provisioning. The female also visited the nest hole but was never witnessed providing any food to the nestlings. Probably, for persuading the chicks to leave the nest hole, both male and female change their behaviour towards chicks such as aggressively waggling the head back and forth, looking into the nest hole without food, withholding the food, visiting of male and female simultaneously the nest hole, and calling from nearby branches.

Before fledging, the male and female nestlings stretch and flap their wings and appear in front of the nest hole (Plate 3.12 and Plate 3.13) to scan around. The nestlings squeeze through the nest opening with the head first, followed by right wing, right leg and then the other body parts, in the presence of parents, welcoming them from nearby branches.

Plate 3.12. Male (left) and female (right) chick looking out of nest hole before fledging

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Plate 3.13. Female nestling, while fledging, squeezing out through nest opening 3.6 Habitat disturbance and threats to hornbill species

The people being poor depend on forest resources. The forest is encroached in order to bring more and more land under cultivation. Swidden agriculture is very common, where the forest plants are slashed and burnt and land is used for the cultivation of upland rice, coconut, banana, vegetables, etc. (Plate 3.14). The effect of these practices leading to habitat destruction is revealed by the fact that nest holes previously reported occupied by both hornbill species were abandoned for many of the last years. The swidden agriculture might not affect the population if only the understory were destroyed but the situation where the large trees are killed and let be dried while standing or a whole area is cleared from its vegetative cover, and nest trees are singled out, leaving big gaps, where the nest holes are directly exposed and birds get very wary to traverse those gaps. Although the Tarictic was found to occupy even the nest hole in a single emergent and near habitation, the disturbance caused by the farmers close to the nest tree more likely aggravates the situation that led to the abandoning of the nest holes.

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Plate 3.14. Swidden agriculture practice, the trees are slashed and burnt for agriculture The poverty of nearby forest inhabitants is a permanent threat to hornbill populations and other wildlife species in the form of hunting, poaching and exploitation of other resources (Plate 3.15 and Plate 3.16).

Plate 3.15. Dulungan nest trees having supports for climbing in order to poach nestlings and/or the breeding female

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Plate 3.16. Monkey trap made by poachers and destroyed by nest guards

The locals are dependent on the forest for timber and firewood, for the construction of houses; big trees are cut down to meet their needs (Plate 3.17). There are also reports from CPMR of illegal logging. The flight feathers of the Tarictic were found away from habitat indicating that they might have been killed by hunters/poachers.

Plate 3.17. A potential hornbill nest tree cut down for timber In some areas, there are permanent residences in/nearby the habitat of hornbills that increase the likelihood of poaching (Plate 3.18). During the breeding season, there had been reports of nest poaching of Dulungan broods.

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Plate 3.18. Agricultural practices and residence near hornbill habitat

In the breeding season 2010 three nest holes of Dulungan were observed where there was clear evidence of nest poaching (Plate 3.15). In case of shortage of suitable nest holes, both species can compete for nest as both species can use the same holes alternatively during consecutive breeding seasons. In addition to probable nest competition between two hornbill species, there might be some other competitors for nest hole. One of the nest holes occupied by the Dulungan during 2009 was occupied by a flying fox during early in the breeding season of 2010 (Plate 3.19). Some hornbill areas are prone to land sliding due to geological/lithological reasons that endangers the forest cover and might affect hornbill populations and other wildlife (Plate 3.20).

Plate 3.19. A Dulungan nest hole occupied Plate 3.20. A hornbill area, impaired by by a flying fox land sliding

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Discussion

Chapter 4 DISCUSSION

4.1 Status and characteristics of nest hole trees

4.1.1 Status of nest hole trees

Hornbills appear to show strong fidelity to their nest sites, with breeding pairs returning year after year to the same cavity (Kemp, 1995; Kinnaird & O'Brien, 2007). The Dulungan pair with the same male was reported to reuse the same nest hole in two consecutive years (Kauth et al., 1998). During 2009 and 2010, nest holes re-occupied by Dulungan (not necessarily by the same individual) were 73% and 62% respectively. A steady decline in the reuse of nests was observed from 77% to 37% for Malabar Grey Hornbill (Mudappa, 2005). In Sulawesi, 50% of Red-knobbed Hornbill nests observed over four years and 60% of those observed for three years were occupied every year. Even same pairs returned to the same nests for three consecutive years. Similarly, in Sumatra, Bushy-crested hornbills returned consistently to the same nest tree over five years (Kinnaird & O'Brien, 2007). 63% of known Malabar Grey Hornbills nests in southern India were used each year by the same species (Mudappa, 2005). Wreathed, Great, Oriental Pied, and Austen’s Brown Hornbills were reported to frequently reuse the nests in and India (Poonswad et al., 1987; Datta & Rawat, 2004). Pairs are capable of breeding consecutive years for a longer period of time (Kinnaird & O'Brien, 2007) or may breed supra-annually only during the mast fruiting events that occur every three to five years on the Borneo (Leighton, 1982).

Dulungans and Tarictics were found using the nest holes of each other in different seasons. In Catmon area, Tarictic occupied the nest hole soon after fledging of Dulungan broods. Exchange of nest sites between hornbill species is common, but what constitute an ideal cavity for each species, availability of cavities and competition for a site between hornbill and other animal species are complex and little studied (Kemp, 1995). The addition of new nest is necessary to compensate abandonment and loss of suitable nests due to natural and human forces. On average, 8 percent of new nest holes of Dulungan were explored every year against 20 percent of Dulungan nests, which remained unoccupied/abandoned. On average, about 7 percent of Dulungan nest holes were taken over by Tarictic during the following season. This means that the availability of existing nest holes may decrease with time due to unsuitability or loss of nest trees with time. In 73

Discussion

Khao Yai, use of available cavities decreased from 94% in 1984 to 50% in 1993 (Poonswad et al., 2005). The addition of new nest holes of Tarictic is higher because in contrast to Dulungan nest holes, which have been searched out for last many years, the Tarictic nests were searched out, first time, during this study. In addition, Tarictic can also use the nest holes, abandoned by Dulungan.

4.1.2 Nest site characters

During two breeding seasons, both species used 43 nest tree species belonging to at least 18 families. There was 35 percent overlap in nest tree species. Tarictic used 16 tree species, which were not used by Dulungan, while Dulungan used 18 tree species, which were not used by Tarictic. With this simple measure of overlap and availability of empty nest holes, apparently there seems no severe competition for nest tree species, however, about 50 percent of Tarictic and 55 percent of Dulungan nest holes were found in trees, which were shared by both species. The shortage of non-shared nest trees may further increase the demand of shared-trees that ultimately may lead to the competition between two species. The exclusive use of a nest tree species by hornbill species could be the outcome of competition in the past.

Most of the Dulungan nests were found in the tree species belonging to the family Dipterocarpaceae, which are favourite nesting trees for all hornbills. Dipterocarps are prone to fungi, which cause heart and butt rot that eventually create the ideal nest cavity for the hornbill (Poonswad, 1991). In contrast to Dulungan, Tarictic used only one nest tree belonging to Dipterocarpaceae (App. 2) that may indicate Dulungan taking advantage of body size for occupying more suitable nest trees and leaving a few for Tarictic. The dipterocarps seem more suitable among tree families as they possess the highest nest holes above ground, largest GBH, and a wide range of elevation above sea level (App. 2). There are comparatively more trees in term of species and numbers that belong to the nest trees, especially of dipterocarps (App. 1). The difference in using different plant species is necessary as described by many biologists that coexisting species must differ in their ecological requirements by at least some minimal amount to avoid competitive exclusion (Pianka, 1974).

The body size of hornbill determines the selection of nest sites as the larger species are supposed to choose bigger trees with higher cavity sites than smaller birds (Kinnaird &

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Discussion

O'Brien, 2007). The hornbills in Khao Yai National Park in Thailand tend to select a nest cavity entrance as well as tree size, according to their body size (Poonswad, 1995). Given their body size, both species have advantages on each other in case of nest shortage and possible competition. Dulungan has an advantage of its body size over smaller size Tarictic. If any direct interference occurs between individuals of two species, it would most likely end in favour of Dulungan, which has less chances of taking over smaller Tarictic’s nest holes. However, Tarictic has an advantage of seeking the nest holes, which do not qualify as suitable for Dulungan. Tarictic used the nest holes abandoned or temporarily left by Dulungan during following breeding season.

4.1.2.1 Nest height and GBH

The criteria for a nest tree, described by Kinnaird & O'Brien (2007) who compiled the data of 14 hornbill species for overall average measurement of various parameters, and concluded that the nest tree is living, over 35m tall and has a diameter at breast height of 98cm (GBH=308cm). Hornbills prefer cavities high in large, living emergent trees (Kinnaird & O'Brien, 2007). The Dulungan used nest trees with significantly higher (11m) nest holes and larger GBH (224cm) than the Tarictic, which used nest (trees) holes with comparatively lower height (7m) and smaller GBH (195cm). Sulawesi Red-knobbed Hornbill, Aceros cassidix (Kinnaird & O'Brien, 1999), Malabar Grey Hornbills (Maheswaran & Balasubramanian, 2003) and Indian Grey Hornbills (Santhoshkumar & Balasubramanian, 2010) are also reported to use tall trees with large girth for nesting. In areas where forests are disturbed and large trees removed, hornbills may be forced into accepting less suitable sites. Visayan Tarictic and the closely related Sulawesi Tarictic hornbill are similar in size (528g vs. 515g), the Visayan Tarictic uses much smaller nest trees (GBH = 107cm vs. 314cm), possibly due to extreme levels of habitat disturbance on Panay island and a lack of large trees (Klop et al., 2000).

The two species are also different in nest characteristic distribution. Nest heights and GBH of nest trees of the Dulungans are non-normally distributed while those of the Tarictics are normally distributed. Contrary to the Tarictic, the histogram for nest heights above ground and GBH of Dulungan nest trees are skewed toward the right and possess even extreme outliers, indicating that the bigger trees, most suitable for nests, especially for Dulungan, are relatively few in number. On the other hand the nest tree species which are not shared by the two species can mitigate the possible competition for nest holes. 75

Discussion

Likewise the distribution range of two species with regard to elevation also differs. The Tarictic are distributed as low as 100m asl while Dulungan starts from 300m asl and goes high above and beyond the distribution of Tarictic, although the difference between the species is not significant. Nest height above ground and GBH increased with elevation above sea level. Similarly, there was a positive significant correlation between nest height above ground and GBH in both species. This increasing trend with elevation might also govern the population trend with elevation as more suitable nest holes are found at higher altitudes. This forest structure may be a result of illegal logging of bigger trees and swidden agricultural practices at lower altitudes near human habitations.

4.1.2.2 Nest orientation

In bird species, the temperature of the clutch during incubation is between 34oC and 38oC (Huggins, 1941; Drent, 1975). To retain this narrow range of temperature during the incubation period, the birds must compensate the heat lost from the clutch with an equivalent input of heat. The quality of the nest, its location, and its orientation with respect to environmental factors, reduces the energetic costs of incubation (Skowron & Kern, 1980). Numerous studies explain the significance of the nest site. Birds orient their nests to obtain the warmth of the morning sun (Hadley, 1969; Orr, 1970) or position the nest so that it is shaded during the hottest part of the day, or out of the sun entirely (Maclean, 1970), and some birds construct their nest on the shielded side of vegetation to minimize the impact of wind (Hadley, 1969).

The cavity opening of hornbill tends to be longer than it is wide (Poonswad, 1995), and may face in any direction. There has been fluctuation in numbers of nest holes facing to a particular direction. The mean compass directions of nest hole entrances used by the Dulungan and the Tarictic during two breeding seasons did not change significantly. The nest hole entrances, used by Dulungan and Tarictic during the two breeding seasons, were evenly distributed in all directions. This pattern of no preference for a particular cavity orientation has been mentioned for Tarictic (Klop et al., 2000), and four other species of Thai hornbills (Poonswad et al., 1987). In India, Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus and Oriental Pied Hornbill albirostris all living sympatrically, have their nest cavities oriented randomly in all directions (Datta & Rawat, 2004). However, the nest orientations of the Malabar Gray

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Hornbill Oceyceros griseus were found significantly oriented toward the north-east direction (Mudappa & Kannan, 1997).

There was no difference between the mean orientations of nest hole entrances of Dulungan and Tarictic hornbills during the breeding season 2009, however, the mean orientation of nest entrances used by the two species during the breeding season 2010 were significantly different. The fluctuation in the mean orientation of entrances may indicate that the selection of using nest holes with different orientations may not be the result of the choice of hornbills. As hornbills cannot excavate nests of their own choice, so the nest orientation may be governed by the availability of nest holes, no matter, in what direction.

4.1.3 Nest competition

The results regarding the competition between the two species for nest trees have multifarious explanations. In the low altitude areas (Malumpati and Kalabanog), where only Tarictics are found, the breeding season coincides with that of the Dulungan. In the areas, where both species breed together, Tarictic may start breeding comparatively very late. In the Catmon area, the Tarictic started breeding soon after fledging of the Dulungan brood. In other areas, Tarictics started breeding sometime after about a month. This later time of breeding parallels results of other studies (Klop et al., 1999; Curio, 2005). This variation in terms of time and space may have different explanations: In the first situation, there is no competitor and nest holes are available merely for the Tarictic without interference of the Dulungan. In the second case, all suitable nest holes might had been occupied and were only available after the vacation of nest holes by the Dulungan. In the third scenario, the suitable nest holes would have been occupied first by the Dulungan, and the Tarictic occupied the remaining nest holes. There are chances of competition for nest holes given their availability that varies from area to area and change in elevation above sea level.

Although there is a significant difference between two species in nest hole selections with regard to nest heights above ground and GBH, the competition between the two species can still not be ruled out. Tarictic can use, and compete for the nest holes suitable for the bigger species of the Dulungan, however, Dulungan has less chance of using comparatively smaller, Tarictic nest holes.

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4.2 Dispersion pattern

The amount of competition for limited resources is one of the most important factors that influences the distribution and density of competing species (Milinski & Parker, 1991; Kacelnik et al., 1992). The mean nearest neighbour distances observed for the Dulungan during both breeding seasons were shorter than the expected nearest neighbour distances if the population were distributed at random. During the second breeding season, the augmentation of new nest holes in the previously surveyed area, increased the population density, decreased the distances between neighbours, and resulted in a more significant deviation from randomness toward aggregation.

The mean observed nearest neighbour distance for the Tarictic, during both breeding seasons, was longer than the mean expected nearest neighbour distance if the population were distributed randomly. In contrast to Dulungan, the Tarictic nests deviated non- significantly from randomness toward regular dispersion. Klop et al. (2000) found nearest neighbour distances shorter than would be expected by regular spacing out of territory owners. According to them the clumping of Tarictic might be due to the patch size that constrains them from attaining an optimal nearest neigbour distance.

The longer observed nearest neighbour distance than the expected nearest neighbour distance of Tarictic broods was likely due to the reason that Tarictic nests were not thoroughly searched out. In addition, the Tarictic nest holes were also found out of forest areas that might have resulted in longer distances. The Clark and Evans ratio between observed and expected nearest neighbour distances apply to homogeneous, contiguous forest. The dispersion pattern for both species was calculated on the total area without considering the gaps between the patches.

The dispersion pattern depicted for both species might not be real, and likely be governed by the distribution of nest trees as hornbills rely on cavities created by other excavators (Poonswad, 1995; Kemp, 1995; Mudappa & Kannan, 1997), and might have been forced to occupy less suitable nest hole trees (Klop et al., 2000).

4.3 Population density

Density estimates are the starting point for monitoring populations and judging the success or failure of conservation and management actions (Gale & Thongaree, 2006).

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Discussion

The increase in the number of breeding pairs of Dulungan from 60 to 100 pairs in 1997 (Klop et al., 2000) to about two thousand breeding pairs is due certainly to the conservation measures initiated by PESCP, which introduced a nest guarding scheme for the critically endangered Dulungan species (Collar et al., 1994). Nest owners have protected the species for the past couple of years, for which they have been given bounties for successful fledging of Dulungan breeding pairs. The reward scheme certainly reduced poaching and hunting of focal species. In addition, besides successful fledging, every year the increment of new nest holes due to exploration of unknown occupied nest holes is also a cause of increase in apparent breeding density. In contrast to the breeding density of Dulungan of 5.73/km2 during the present study, Klop et al. (2000) estimated a density of about 0.2-0.3 nest/km2 in 1997. This very low population density estimate by Klop was based on two Dulungan nests. During the present study, most of the nest holes were well known to nest owners who get a reward for (every searched nest hole and) successful fledging. Gale & Thongaree (2006), in southern Thailand, also estimated very low population densities of other related hornbill species like Plain-pouched (Aceros subruficollis) (0.09 individual/km2), White-crowned (Aceros comatus) (0.08 individual/km2), Wrinkled (A. corrugatus) (0.08 individual/km2), and Wreathed (A. undulatus) (0.69 individual/km2).

Conservation measures taken for a critically endangered species of Dulungan under a reward scheme simultaneously benefited the sympatric Tarictic Hornbill and associated wildlife species. Klop et al. (1999) estimated a total population of Tarictic in CMPR of 750-1500 breeding pairs with nest density of three per kilometer square in the breeding year 1997. Tarictic breeding pair density of 5.83/km2 might be underestimated because the nest holes were not searched as thoroughly as Dulungan nest holes were. The population densities of both species coincide with a population density of 6 individuals/km2 of the endemic Sumba Hornbill, Aceros everetti in Sumba Island, Indonesia (Sitompul et al., 2004). In Sulawesi Red-knobbed Hornbill Aceros cassidix, nest density was estimated as 10 pairs/km2 (Kinnaird et al., 1996). The nesting density of both species relative to the availability of suitable empty nest holes suggests that nests are not limiting, and population density may further increase if current conservation measures are continued.

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4.4 Food and feeding ecology

4.4.1 Fruit species consumed

Hornbills appear to select fruits that, on average, provide superior energetic rewards and usually more protein per fruit than those eaten by other birds and mammals (Kinnaird & O'Brien, 2007). The diet of 17 Asian hornbill species reveals the importance of fruits, which constitutes about 63% to 98% of the diet, with highly variable animal diet ranging from 1-37% (Kinnaird & O'Brien, 2007). The fruit species consumed by the Dulungan and the Tarictic during two breeding seasons belonged to about 24 families, 31 genera and 52 species. The most fruit species belonged to families Myristicaceae (5 species), Myrtaceae (3), Palmae (3), Moraceae (2), and Meliaceae (2). Fruits of Myristicaceae and Meliaceae are dehiscent pods with bright, oily arils that surround the seeds while the fruits of palm are lipid rich drupes. In Asian hornbills, lipid-rich drupes account for the majority of fruit species eaten (42%), followed by dehiscent, arillate species (30%) and figs (12%) (Kinnaird & O'Brien, 2007). The top five diet families ranked by members of species consumed by 17 species of well-studied Asian hornbills are Lauraceae, Moraceae, Meliaceae, Myristicaceae, and Annonaceae (Kinnaird & O'Brien, 2007).

The Dulungan showed a wider feeding spectrum (n=51 fruit species) than Tarictic (n=38 fruit species), probably one of the reasons may be that more breeding pairs of the former, in term of seed collection, were sampled. Klop et al. (1999) have reported the Tarictic using at least 48 fruit species belonging to 25 families, during the breeding season. Both, Black and Red-knobbed Hornbills used 52 fruit species, followed by Wreathed Hornbills (58 sp.) and Bushy-crested Hornbills (94 sp.) (Kinnaird & O'Brien, 2007). The Dulungan and the Tarictic used different numbers of fruit species during two breeding seasons (41 sp. in 2009 and 48 sp. in 2010). This variation probably reflects local differences in fruit availability on an annual basis rather than real dietary switching strategies (Witmer & van Soest, 1998) as new nest holes and areas were added during the second breeding season.

Fruit colour

All Asian hornbills eat ripe fruits. Colour and texture are the cues used by hornbills and other birds to determine if a fruit is ripe (Gautier-Hion et al., 1985). During direct observation, Tarictic males most frequently delivered reddish blue fruits, other fruit colours were black, red, orange, and purple. The consumption of red fruits, followed by

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Discussion

(purple-) black and orange by Tarictic during the breeding season is also documented elsewhere (Klop et al., 1999). Red-knobbed Hornbills preferentially select fruits that ripen to red, purple, or black (Suryadi et al., 1994), and similar selection criteria were found in Thai hornbills (Kitamura et al., 2002). Colour is undoubtedly the first cue hornbills use to locate ripe-fruit patches. Once they enter a patch, they make a final ripeness test by squeezing fruits with their bills; colourful but still hard fruits are left on the tree or tossed to the ground. Hornbills, consuming ripe fruits with mature seeds, fulfil the first requirement for a good disperser (Kinnaird & O'Brien, 2007).

4.4.2 Interspecific competition

Although both hornbill species differ in size, their overall diet overlap was quite high.

Both species shared 37 fruit species, giving an overall diet overlap of Is=83 percent. Tarictic, during the 2010 shared all 26 (100%) fruit species with Dulungan, with 70% overlap. This very high overlap for fruit species of sympatric hornbills, may indicate that the fruits are either superabundant or hornbill diet trees occur at low densities, forcing more birds to feed on fewer resources (Kinnaird & O'Brien, 2007). The two species may get into a severe competition during the period of shortage of fruits. However, the high diversity indices for both species seem to meet their requirements. Moreover, the Tarictic using animal food can also mitigate the competition between the two hornbills.

An increase in the number of competitors reduces an individual's food intake (Hassell & Varley, 1969; Sutherland, 1983), however, if resources are not in short supply, two organisms can share them without harm to one another. Thus, high niche overlap may actually be associated with reduced competition. Similarly, disjunct niches may often indicate avoidance of competition in situations where it could potentially be severe (Pianka, 1974). In forests where more than one species of hornbill share the fruit resources, the potential for diet overlap is great. From the hornbills’ perspective, however, diet overlap means having to share potentially limited fruit resources with others. This, of course, stimulates the likelihood of competition (Kinnaird & O'Brien, 2007).

Sympatrically living species with limited resources may partition the available resources and time in order to coexist. They may consume different food items, may use different strata for foraging, or may forage at different time, in order to avoid competition (Schoener, 1974; Cody, 1985; Rosenzweig, 1995). This competition can be further

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Discussion avoided as both species differ in minimum and maximum altitudinal ranges. The Tarictic breeds as low as 100m up to 600m asl while the Dulungan breeds above 300m and goes up beyond 750m asl. This difference in the altitudinal distribution might be a result of spatial partitioning to avoid consequences of competition for resources, where Tarictic can breed in the smaller nest trees unsuitable for Dulungan or may be the consequence of preferring different fruits.

Gape Size: Hornbills have wide gapes that allow them to swallow large fruits whole, and their relatively big body sizes enable them to fly with heavy bulks (Kinnaird & O'Brien, 2007). Dulungan has an advantage of exploiting more fruit species than Tarictic owing to the large body and gape size. During 2010, the Dulungan used 22 of those fruit species, which were not found in the diet of the Tarictic. Hornbills preferentially choose fruits in the 20-30mm range, passing up fruits smaller than 10mm and larger than 50mm. Similarly, hornbills tend to select fruits in the 1-10g range more often than expected and ignore fruits weighing less than 1g. Fruit larger than 50mm is hard to swallow (Kinnaird & O'Brien, 2007). The maximum gape width of 55mm has been reported for large Buceros hornbills (Leighton, 1982). Dulungan being larger than Tarictic, with comparatively wider gape, can exploit larger fruits, which the Tarictic cannot manipulate. This advantage of gap size can reduce the confrontation between the two species over fruits.

Hostility: Curio (2005), during the breeding season, observed a Dulungan male chasing a Tarictic while passing by his nest tree during incubation, but he also reported more than two Tarictics chasing Dulungan. According to him, these encounters may be the result of territoriality rather that competition for food as no such skirmishes were observed between hornbills and other frugivores. Hornbills engage in indirect competition when one species eats the resources before another gets there and direct competition when one hornbill displaces another from a fruiting tree (Kinnaird & O'Brien, 2007). During field surveys, no direct hostility for food and nest holes was observed between individuals of the same or two species of hornbills, however, Curio (2005) during the breeding season, observed a Dulungan male chasing another from a fruiting tree. Displacement can be as subtle as one species quietly leaving as another enters, or it can turn dramatic with chases, branch shaking, and calling (Kinnaird & O'Brien, 2007). During the study period, both hornbill species were never observed together on fruiting trees or otherwise. This might be because two hornbills do not feed simultaneously on the same tree but many Dulungan 82

Discussion

Hornbills were found feeding at a time on the same fig trees (Curio, 2005). The maximum number of Dulungans encountered during the field surveys was a group of six males and four females on a Dalakit tree (Ficus sp.). The largest flock of Dulungan ever recorded, was a post-breeding flock of 25-30 individuals, feeding on the ripe fruits of Aglaia sp. near Dalagsaan, Aklan Province (Curio et al., 1996b). This might indicate the avoidance of two species of possible encounters and resource partitioning in terms of fruit consumption and/or timing. Among nonterritorial species, hornbills may avoid conspecifics by deciding to visit trees at different times (Kinnaird & O'Brien, 2007). Leighton (1982) found that Bornean hornbills rarely fed in the trees at the same time and experienced low rates of aggressive interactions. Bushy-crested Hornbills visited fruit trees earlier than did other hornbills, followed closely by White-crowned and Black Hornbills (Kinnaird & O'Brien, 2007).

4.4.3 Nearest neighbour food overlap

4.4.3.1 Intraspecific nearest neighbour food overlap

The pooled data as well as the data fitted separately to inter-and intraspecific food overlap of the Dulungan and the Tarictic show a negative correlation between nearest neighbour distance and food overlap during both breeding seasons. This consistent pattern in all instances may indicate that an increase in the distance between two neighbouring broods may reduce the chance of two individuals to come to use the same fruit resources. Two broods living close together may be forced to rely on the same fruit species available in their habitat and close to their nest trees in order to optimize their time and energy. In case of long distances, vast area with more diversity of fruit species will provide more chances for broods to utilize different fruit species in the vicinity/habitat/territory, without conflict with other individuals.

Examining the pair-wise hornbill broods for evaluating the overlap of food between two neighbouring broods, there was a wide range between no-overlap to 100% overlap in the diet of intraspecific nearest broods, while in interspecific nearest broods, the overlap is very low, with many broods having no overlap. For foraging optimality (MacArthur & Pianka, 1966), in principle, the diet should have been indistinguishable and two neighbouring broods of the same species should have 100 percent overlap in their food consumption as both neighbouring broods belonging to same species have the same food

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Discussion requirements. The difference in the overlap might indicate the limiting food resources, which leads to partitioning of resources in order to mitigate competition. Most species defend territories only against their own species, which would compete directly for the same resources, with the result that up to eight species of hornbill with different feeding habits often coexist in a complex mosaic of overlapping territories (Kemp, 1995).

Even in case of 100% overlap, as a strategy, the members of the same species may divide themselves into small foraging parties and feed separately. In order to reduce competition, Bushy-crested Hornbills and White-crowned Hornbills adjust foraging group sizes to compensate for fruit patch sizes (Leighton, 1982). Similarly, Sulawesi Tarictic hornbills often split into subgroups when foraging on small understory and mid-canopy fruit trees (Kinnaird & O'Brien, 2007). The variation in overlap may also be due to the variation in fruiting phenology during different seasons and in different nest site habitats. Of 52 fruit species consumed by both hornbills, the average number of fruits consumed by a brood was very low (6.2 fruits per brood), indicating that fruits are not evenly distributed, and at different sites, hornbills have access to a few fruit species. With these limited numbers of fruit species available, the diet overlap should have been high because broods would have few choices among fruit species, but this is not true for most of the broods. There is even no overlap in fruit species, which may indicate competition between neighbouring broods, leading to partitioning of fruit resources. According to niche overlap hypothesis, the maximal tolerable niche overlap should decrease with increasing intensity of competition (Pianka, 1974), and two competing species can coexist when intra-specific competition is greater than interspecific competition (Armstrong & McGehee, 1980).

4.4.3.2 Interspecific nearest neighbour food overlap

Unlike intraspecific nearest neighbour, the interspecific nearest neighbour food overlap was very low, with many neighbours having no overlap. Comparatively weak and non- significantly negative correlation between distance and food overlap might be due to the long distance and low food overlap. Low or no interspecific food overlap may be a consequence of shifting in food consumption that varies for two different species, long distances between nearest neighbours, different food requirements, and gape size. This difference is also understandable as there are more than twenty fruit species, which were only used by Dulungan but not by Tarictic. However, an overall overlap of 83% is very high compared to the diet overlap between neighbouring broods of two species. Among a 84

Discussion wide range of fruit species used by both species, individual breeding pair used fruits belonging to a few species. Same pattern was documented in Northeast India, where three sympatric hornbills used a few common species for the bulk of their diet (Datta & Rawat, 2003). African forest hornbill (Ceratogymna sp.) was reported consuming the fruits of over 100 species with 60 percent of diet contributed by only ten diet species (Martinez del Rio & Restrepo, 1992).

Two neighbouring broods with long distances, consuming different fruit species, might also be a consequence of different fruit phenology at distant nest site habitats that in turn shapes different intensity levels of fruit overlap. This phenomenon has also been mentioned in Thailand, where diet overlap averages 71%. The Great, Wreathed, and Oriental Pied Hornbills of Thailand share three times more of their diets as the same species pairs in northern India (Kinnaird & O'Brien, 2007). Austen’s Brown Hornbill and Oriental Pied Hornbill of Thailand share about 89% of their diet. In contrast Helmeted Hornbill and White-crowned Hornbill of Sumatra share 0% of their diet (Kinnaird & O'Brien, 2007).

Hornbills begin to specialize on particular genera, resulting in a decline in dietary diversity. Helmeted Hornbills, for example, rely heavily on figs, and this is reflected by the extremely low diversity of fruits recorded in their diet (Kinnaird & O'Brien, 2007). Besides other factors, the difference in diet overlap between the neighbouring brood of Dulungan and Tarictic might also be a consequence of specialization of two species for exploiting different kinds of fruits available near the nest site.

4.5 Breeding biology of the Dulungan and the Tarictic

4.5.1 Timing of breeding

The timing of nesting in hornbills is thought to be an adaptation to cope with seasonal pulses in food availability (Leighton, 1982; Kemp, 1995). Hornbills nesting in the equatorial region of Indonesia, Malaysia, and the Philippines, experience seasonal and aseasonal climates (Kinnaird & O'Brien, 2007). The Dulungan started breeding usually in early March and fledging mostly in late June and early July. In some areas, the nest holes were found fledged in the end of May, meaning that the breeding might have been initiated in the end of February. The nest holes that were still sealed in the end of July indicate that breeding was started in the end of April. In Hamtang forest, the Dulungan 85

Discussion started breeding in early March when nest holes were found sealed, while at the Sibaliw, fledging started already in mid-May (Kauth et al., 1998).

The Tarictic breeding period started in mid-March and ended in July. There was no evidence during the study period that Tarictic, like Dulungan, would have started in February or beginning of March. The taking over of the same nest hole after fledging of Dulungan in Catmon area indicates that Tarictic starts breeding later than Dulungan. It can be inferred from the variation in breeding time of both species that depending on the nest and food availability, Tarictic may start at least 15 days to two months later than Dulungan. All Tarictic nest holes, where breeding was recorded in mid-March, were Dulungan free areas without any competition for resources. The difference in breeding activity of Tarictic has also been reported by other researchers, who have documented starting of breeding from the second week of March to the first week of April (Klop et al., 2000; Dickinson et al., 1991). The duration of nesting initiation is irregular within species, and even in the seasonal environments, the process may be highly synchronized or can dribble on for more than three months (Kinnaird & O'Brien, 2007).

A time difference in breeding initiation within a species has also been found in other hornbill species. Great and Wreathed Hornbills initiate nesting over a two-month period, beginning in January, and Oriental Pied and Austen’s Brown Hornbills at the same site also initiate nesting over a two-month period (Poonswad et al., 1987; Poonswad et al., 1999). Species, nesting in aseasonal area, typically enter their nest over a span of four to six months, although Bushy-crested and Wreathed Hornbills initiate nest throughout the year (Kinnaird & O'Brien, 2007).

Hornbills, during the courtship, increase allopreening and allofeeding, initiated mainly by the male, which leads to courtship feeding, and the female no longer needs to collect her own food (Kemp, 1995). Before the commencement of breeding, the Dulungan male and female were found in the fruiting tree, where the male was observed offering fruits to the female. The results of the present study regarding provision of fruits during preparation and cleaning of the nest hole, and the material used for nest sealing, coincide with previous studies for many hornbill species (Kemp, 1995; Tsuji, 1996; Kinnaird & O'Brien, 1999; Kinnaird & O'Brien, 2007).

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4.5.2 Clutch size, brood size and fledging

Only one clutch size of three eggs of Dulungan could be observed during the incubation period. Kauth et al. (1998) documented fledging of three chicks of Dulungan, where the breeding female left the nest one day after fledging of first chick. In the Indonesian island of Sulawesi, Red-knobbed Hornbill (Aceros cassidix) is also reported being capable of having a clutch size of up to three eggs, although only one chick per nest fledged (Kinnaird & O'Brien, 1999). Comparing with Red-knobbed Hornbill, which is bigger than the Dulungan, the fledging of three chicks in Dulungan is not unreasonable as smaller- bodied hornbills have larger clutches (Kinnaird & O'Brien, 2007) and in larger-bodied hornbills, extra eggs rarely hatch or extra hatchlings die within a few days (Kemp, 1995).

In Malumpati, three eggs of Tarictic were found in the nest hole. In the Calabanog area, two chicks, a male and a female, fledged during the observation period of five days. The nest was unsealed, and female had already left, which poses doubt if any chick had already fledged with the breeding female. Klop et al. (2000) observed an incarcerated breeding-female leaving the nest after fledging of the first nestling. Kemp (1995) has reported a clutch size of two, while in Sibaliw, one nest fledged two nestlings, and another contained three nestlings, the smallest of them was found dead under the nest tree (Klop et al., 2000). From observations during fledging period of the Tarictic, it can be inferred that the female leaves the nest hole at least five days before the last chick fledges. For a sample of 21 hornbill species, 62% of the females emerged anywhere from 5 days to 1.5 months before the chicks fledged (Kinnaird & O'Brien, 2007).

The Tarictic breeding in unsealed opening, protected only by adventitious roots and branches, and a cavity in a rock crevice in the Malumpati area, are unique. The Tarictic Hornbill nest in the rock (cliff) is also reported elsewhere by locals (Curio et al., 1996a). Monteiro’s Hornbill Tockus monteiri also places its nest in rocky cavity within cliff (Kemp, 1995). This adaptation of the Tarictic may be due to the shortage of suitable nests in the Malumpati area that force Tarictics to use unsealed nest holes, vulnerable to poachers and predators. Breeding in the crevice might be due to threats as the area is nearer to human habitation, and inaccessible steep cliffs might be a better choice to reduce the threat of poaching.

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4.5.3 Moulting of feathers of the breeding female

Collection of feathers after the breeding season indicates that breeding females of both species moult their flight feathers during the nesting period. According to Kemp (1995), the breeding female in the genus Aceros moults rectrices and remiges simultaneously while incubating, and becomes temporarily flightless. However, complete moult of flight feathers, and moulting patterns during nesting are variable within and between hornbill species (Kinnaird & O'Brien, 2007). From some occupied nest holes, very few or no feathers were recovered, which might be the result of variability in moulting. Moults of smaller species of hornbills are most regular, most frequent, and shortest in duration, while in larger species, a complete replacement of all feathers may be spread over several years (Kemp, 1995). The Great Hornbill either moults her flight feathers completely or do not moult at all (Poonswad et al., 1983), and partial moulting of feathers is also reported (Kannan & James, 1997) in the same species. In captivity, during the breeding season, Great Hornbill, Rhinoceros Hornbill and Red-knobbed Hornbill all show a pattern of normal, progressive moult (Kinnaird & O'Brien, 2007). Female Malabar Great Hornbill was observed to retain her tail feathers throughout the nesting period, although some rectrices were collected from a midden that indicates partial moulting in this species (Mudappa, 2000).

4.5.4 Behavioural observations during the breeding season

During the breeding season, Dulungan and Tarictic males were found vigilant, remaining silent, probably concealing themselves and their broods. According to Curio (2005), during the nesting period, males of both species become silent in the vicinity of their active nests and even avoid swishing wing noises. In case of any intruder, the Tarictic becomes silent and motionless (Rabor, 1977). The Tarictics were encountered/detected more frequently due to their frequent calling. They are silent when being approached, possibly due to intense hunting (Curio, 2005), however, on anticipating any disturbance, or change in their habitat, both species were found avoiding to visit the nest. On many instances, instead of approaching the nest hole, the male delayed food delivery to the brood. Sometimes male uttered alarm calls while flying restlessly around, and even was accompanied by other fellow members. The Tarictic fall victim to hunters when a member of the group is shot down others rush towards the victim, in so doing becoming

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Discussion easy targets for the hunter, in this way whole groups could be wiped out (Curio, 2005). While feeding, the male of both species did not visit the hole directly; instead, the male first perched on distant trees, scanned environ and then approached the nest hole silently or gave a soft call. The habituation of the male to a new structure varies depending on the degree of previous interaction with humans.

During the fledging period, in most of the species, the delivery of food to the nest declines in the last weeks of provisioning. However, the visitation to the nest vicinity by parents increases without food delivery (Kinnaird & O'Brien, 2007). Observation of the Tarictic brood during the fledging period showed the same behaviour of visiting of male and female to the nest without providing any food. The parents try to persuade the chick out of the nest by sitting in sight of the nest, calling and withholding food, despite repeated begging by chicks (Kinnaird & O'Brien, 2007). In Sibaliw, Kauth et al. (1998) observed a male Dulungan visiting the nest tree repeatedly without any food between visits with food. In the Brown Hornbill, the breeding male and his helpers turned up at the nest with food but instead of actuallly feeding the chick, they attracted it with the piece of food. This baiting sequence was repeated several times, provoking the female to break the nest plaster and emerge, the chick followed her out (Tsuji, 1996).

Before fledging, the hornbill nestlings begin to flap their wings as if there were flying exercise prior to fledging (Tsuji, 1996). The same activities were noted during observations of the Tarictic brood before fledging, where both male and female nestlings were observed stretching and flapping their wings inside the nest, and exposing themselves in front of a nest hole to scan the environs. The fledglings push themselves out into the unknown but instinctively familiar world (Tsuji, 1996), in the presence of parents waiting for their fledging. The fledging in the Tarictic took place early in the morning. Fledging in the afternoon has never been observed. If fledging trials fail, the chick defers fledging until the next morning that probably provides enough time for the chick to adapt itself to its new environment and thus not fall easy prey to predators at night (Tsuji, 1996).

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Conclusions and Recommendations

Chapter 5 CONCLUSIONS AND RECOMMENDATIONS

The following conclusions are drawn from the present study of Dulungan and Tarictic during their breeding seasons:  A total of 43 nest trees, belonging to 18 families with an overlap of 35%, were used by two species of hornbills. Preferred nest trees of the Dulungan include Libtog, Balakbakan and Taba-aw. The nest hole trees occupied by Tarictic belonged to Libtog, Maganhop, Bagilomboy, Malabuyo, Salong and Toog. Both species preferred to nest in the main stem and reused the nest trees (by the same species) in the following season.  Nest height above ground and elevation above sea level were positively correlated. Trees with larger GBH have higher nest holes above ground. The Dulungan used significantly bigger trees with larger girth, and significantly higher nest holes above ground than the Tarictic.  The nest hole entrances used by both species during the both breeding seasons were evenly distributed in all (compass) directions. Both species may differ in the use of nest holes with significantly different mean orientations of entrance during different breeding seasons. The selection of nest may not be due to the choice but the availability of holes with any direction.  In spite of differences in the time of breeding initiation and occupying the nest after fledging of the Dulungan brood, the difference in nest site selection, nest characteristics and empty nest holes found in the area indicate that at present there may not be an obvious overall competition for the nest, however, nest competition may occur on some sites.  The dispersion pattern of the Dulungan indicates a significant deviation from randomness in the direction of aggregation, while the Tarictic showed a tendency in the direction of regular dispersion.  Dulungan and Tarictic breeding pair density was 4.47/km2 and 5.83/km2, respectively, and the population of 1787 breeding pairs of Dulungan and 2333 breeding pairs of Tarictic was estimated in the CPMR. The empty suitable nest holes may also indicate that the population of Dulungan is under carrying capacity, which might be the result of hunting and poaching as observed during field surveys.  The Dulungan was recorded between 280m and 800m asl, and the Tarictic between 100m and 610m asl. The population of both species increased with elevation up to a certain level, after which the population showed a declining trend. Two species showed no difference in the number of breeding pairs when controlling for elevation above sea level.  The fruits delivered during the breeding seasons belonged to about 24 families, 31 genera and 52 species. The most common families were Myristicaceae, Myrtaceae, Palmae, Moraceae and Meliaceae. Dulungan and Tarictic used 51 and 38 fruit species respectively, with an overall diet overlap of 83 percent. This higher overlap indicates that the competition for same fruits can occur between two hornbills during the period of fruit shortage.

90

Conclusions and Recommendations

 Dulungan used fruits of Planchonia spectabilis, Canarium sp. and Sandoricum koetjape frequently, and Meliaceae, Myristicaceae and Lecythidaceae were preferred families. Tarictic used Canarium sp., Planchonia spectabilis and Prunus fragrans and the preferred fruit families belonged to Sapotaceae, Myristicaceae and Burseraceae. The Dulungan is more of a generalist with regard to fruit consumption than the Tarictic. The Dulungan, during the breeding, depends totally on fruits while the Tarictic also supplements its diet with animal food.  The food overlap between the nearest neighbours of the same species ranged from 0- 100%. The nearest neighbour distance and overlap of fruit species were negatively correlated for both species. This overlap in the diet might be due to shortage of fruit.  Tarictic food during fledging was composed of 97.5% of fruits and 2.5% of animal food that comprised of grasshoppers, beetles, flies, lizards and insects.  Interspecific food overlap was low (66%) with comparatively very weak correlation between nearest neighbour distance and food overlap, indicating a shift in the diet to avoid competition between neighbouring species.  Breeding period of the Dulungan and the Tarictic spans, respectively, from early March to early July and mid-March to end of July. Breeding commences with courtship feeding followed by nest cleaning and sealing by the female. Females of both species lay about 3 eggs and moult their flight feathers in the nest hole.  Male of both species showed nest concealment behaviour. The time of habituating to the change in environ varied, depending on the interaction of the bird with human activities. The male is a sole food provider to nestlings, which, while feeding, usually regurgitated the first food items on a nearby branch. Food withholding behaviour was shown by the male during fledging. After fledging, nestlings are received by their parents waiting outside the nest.  The difference between the two species in using different nest sites, the difference in elevation range, the Tarictic using low canopy and isolated trees, difference in breeding time and food composition might be an indication of an ecological separation of the two species due to competition for resources.  Poor local inhabitants, dependent on forest resources to meet their daily living, pose a constant threat to habitat, hornbill populations and other wildlife species in the form of swidden agriculture, hunting, poaching, timber and firewood cutting, and exploitation of other resources.  Population increase from less than 100 pairs to 2000 pairs of Dulungan apparently owes to the conservation measures of PESCP, started by Prof. Eberhard Curio. This increase over time also reflects the increase of the number of holes guarded: i.e. the number of guards recruited. However, illegal activities are still taking place in the area. In order to cope with this situation there is a need to recruit more, professionally trained staff. The local people adjacent to CPMR should be preferred for recruitment of new staff.  The area is surrounded by many villages and can be accessed easily. There is a need to develop a watch and ward system involving local communities of hornbill areas. It is recommended to establish permanent checkpoints at main entry points to the CPMR. This will help reduce the illegal activities to some extent.

91

Conclusions and Recommendations

 It is worth mentioning that the withdrawal of the nest reward scheme can further intensify hunting and poaching of hornbill species and destruction of habitat that may reverse the current population status and hence be a setback to all conservation measures taken so far. It is therefore, recommended to continue the nest reward scheme.  The conservation education and awareness programme initiated by PESCP should continue to highlight the importance of biodiversity and its role in maintenance of a healthy environment.  There is an immediate need for a complete ban on swidden agriculture and permanent residence in hornbill areas.  Whole communities should be involved in conservation measures that will give them a sense of ownership.  In order to evaluate the fruit supply/availability and demand/consumption by hornbills, a detailed study on fruiting phenology is recommended to be conducted in the CPMR that will help reveal a clear picture, if any, of competition for fruits.

92

References

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Appendices

Chapter 7 APPENDICES

App. 1. Tree species found in the vicinity of nest trees occupied by hornbills during their breeding seasons Local name Scientific name Family No Percent Alibot - - 1 0.2 Almon Shorea almon Dipterocarpaceae 3 0.7 Alopag - - 5 1.1 Amogis Koordersiodendron pinnatum Anacardiaceae 1 0.2 Anepga - - 2 0.5 Atay-atay Pseuderanthemum bicolor Acanthaceae 1 0.2 Ayo Casuarina equisetifolia Casuarinaceae 18 4.1 Badlan Radermachera pinnata Bignoniaceae 14 3.2 Bagilomboy Syzygium bordenii Myrtaceae 1 0.2 Bago-arom - - 1 0.2 Baid - - 3 0.7 Bakan Platea excelsa Icacinaceae 3 0.7 Bakan-bakas - - 1 0.2 Balakbakan Shorea sp. Dipterocarpaceae 41 9.3 Balasbas Odontonema nitidum Acanthaceae 2 0.5 Balod Neonauclea lanceolata Rubiaceae 5 1.1 Bangkalawag Neonauclea calycina Rubiaceae 15 3.4 Bang-og - - 2 0.5 Baniko - - 1 0.2 Banilad Sterculia philippinensis Sterculiaceae 2 0.5 Basalayan - - 2 0.5 Batikulin Areca catechu Palmae 1 0.2 Bayog Pterocymbium niveum Sterculiaceae 8 1.8 Bha - - 1 0.2 Binunga Macaranga bicolor Euphorbiaceae 1 0.2 Biri Ficus sp. Moraceae 12 2.7 Bita Alstonia scholaris Apocynaceae 3 0.7 Bunot-bunot - - 1 0.2 Dalakit Ficus sp. Moraceae 9 2.0 Dangola - - 2 0.5 Danlog Shorea contorta Dipterocarpaceae 1 0.2 Deladanga - - 1 0.2 Dilat - - 1 0.2 Dingon - - 1 0.2 Dogoan - - 1 0.2 Dublahan - - 1 0.2 Duguay Myristica philippensis Myristicaceae 1 0.2 Dural-og Ficus nota Moraceae 3 0.7

101

Appendices

Local name Scientific name Family No Percent Gugo Ganophyllum falcatum Sapindaceae 2 0.5 Haras Hopea plagata Dipterocarpaceae 6 1.4 Indang Myristica cumingii Myristicaceae 3 0.7 Inyam Antidesma ghaesembilla Euphorbiaceae 1 0.2 Jakya - - 1 0.2 Kabahoy - - 2 0.5 Kabnol - - 1 0.2 Kalantas Toona calantas Meliaceae 4 0.9 Kaluluto - - 2 0.5 Kaluntingan Neonauclea vidalii Rubiaceae 6 1.4 Kanapay Artocarpus nitida Moraceae 8 1.8 Kaningag Litsea cumingiana Lauraceae 1 0.2 Katmon Dillenia philippinensis Dilleniaceae 4 0.9 Kogaram - - 1 0.2 Kurotingan - - 3 0.7 Lagasi Horsfieldia ardisiifolia Myristicaceae 5 1.1 Lagusip - - 1 0.2 Lakas - - 1 0.2 Lantas - - 4 0.9 Lapahao - - 1 0.2 Lawa-an Shorea guiso Dipterocarpaceae 41 9.3 Lawihaw - - 2 0.5 Libtog - - 31 7.0 Limanog - - 1 0.2 Lunok Ficus sp. Moraceae 5 1.1 Maganhop - - 2 0.5 Magbinlod Syzygium sp. Myrtaceae 1 0.2 Magilomboy - - 4 0.9 Malabuyo Alangium meyeri Alangiaceae 1 0.2 Malagabie - - 1 0.2 Malakacis - - 1 0.2 Malakajun - - 1 0.2 Malig-ang Shorea sp. Dipterocarpaceae 1 0.2 Manajos - - 1 0.2 Manyabot - - 1 0.2 Marobo Cinnamomum mercadoi Lauraceae 4 0.9 Maugang - - 1 0.2 Nakajis - - 1 0.2 Nangag - - 1 0.2 Narra - - 1 0.2 Nato Palaquium sp. Sapotaceae 5 1.1 Nipga - - 5 1.1

102

Appendices

Local name Scientific name Family No Percent Olamo - - 1 0.2 Oropag - - 1 0.2 Paho Mangifera indica Anacardiaceae 3 0.7 Pili Canarium sp. Burseraceae 2 0.5 Plumangog - - 1 0.2 Prali - - 1 0.2 Puron - - 1 0.2 Putian Vatica sp. Dipterocarpaceae 8 1.8 Salin-Urang - - 2 0.5 Salin-uwak Ellipanthus tomentosus Connaraceae 3 0.7 Salong Canarium asperum Burseraceae 7 1.6 Serali - - 1 0.2 Taba-aw Aglaia sp. Meliaceae 12 2.7 Tabahoy - - 2 0.5 Taguili - - 1 0.2 Taluto Pterocymbium tinctorium Sterculiaceae 2 0.5 Tamlang - - 2 0.5 Tawaa Flagellaria indica Flagellariaceae 1 0.2 Toog Bischofia javanica Euphorbiaceae 19 4.3 Tul-ang - - 11 2.5 Tula-tula Mallotus floribundus Euphorbiaceae 1 0.2 Tul-ay Alphitonia philipinensis Rhamnaceae 1 0.2 Ughayan - - 2 0.5 Upong-upong vidalii Lauraceae 2 0.5 Uya-oy Planchonia spectabilis Lecythidaceae 7 1.6 Yabot - - 6 1.4

103

Appendices

App. 2. Characteristic parameters of nest trees occupied by two hornbill species during two breeding seasons (T=Tarictic, D=Dulungan: subscript indicates number of nest tree species, GBH= Girth at Breast Height, Mean= arithmetic mean, Orientation=compass direction). Dulungan Tarictic Family Local name Scientific name Nest parameter N Mean SD Range N Mean SD Range Alangiaceae Malabuyo Alangium meyeri Nest Height(m) - - - - 2 5 - 3-7 GBH(cm) - - - - 2 172 - 160-183 Altitude(m) - - - - 2 430 - 320-540 Orientation - - - - 2 - - 225-360 Anacardiaceae Lawihaw Dracontomelon dao Nest Height(m) 2 11 - 9-12 - - - - GBH(cm) 2 198 - 196-200 - - - - Altitude(m) 2 495 - 490-500 - - - - Orientation 2 - - 95-175 - - - - Arecaceae, Palmae Buri Corypha utan Nest Height(m) 1 12 ------GBH(cm) 1 206 . - - - - - Altitude(m) 1 590 . - - - - - Orientation 1 ------

Burseraceae Salong(D,T2) Canarium asperum Nest Height(m) 2 8 - 4-12 3 3 2.9 1-6 Pili(D,T) Canarium sp. GBH(cm) 2 209 - 167-250 3 152 52.6 120-213 Altitude(m) 2 620 - 460-780 3 327 235.4 100-570 Orientation 2 - - 130-242 3 - - 170-250 Casuarinaceae Ayo Casuarina equisetifolia Nest Height(m) - - - - 1 18 - - GBH(cm) - - - - 1 203 - -

104

Appendices

Dulungan Tarictic Family Local name Scientific name Nest parameter N Mean SD Range N Mean SD Range Altitude(m) - - - - 1 540 - - Orientation - - - - 1 - - - Cunoniaceae Palad Weinmania hutchinsonii Nest Height(m) - - - - 1 8 - - GBH(cm) - - - - 1 96 - - Altitude(m) - - - - 1 560 - - Orientation - - - - 1 - - -

Dipterocarpaceae Balakbakan(D15,T) Shorea sp. Nest Height(m) 25 12 4.0 4-20 1 7 - -

Lawa-an(D6) Shorea guiso GBH(cm) 25 288 122.4 130-665 1 180 - -

Danlog(D2) Shorea contorta Altitude(m) 25 519 111.1 315-700 1 535 - -

Putian(D2) Vatica sp. Orientation 25 - - 27-345 1 - - -

Euphorbiaceae Toog(D2,T2) Bischofia javanica Nest Height(m) 2 10 - 9-11 3 7 3.2 5-11 Kamantugan(T) Neotrewia cumingii GBH(cm) 2 235 - 206-264 3 164 32.7 130-195 Altitude(m) 2 350 - 310-390 3 400 62.5 330-450 Orientation 2 - - 20-100 3 - - 75-360 Guttiferae Palomaria Calophyllum sp. Nest Height(m) 1 8 ------GBH(cm) 1 157 ------Altitude(m) 1 440 ------Orientation 1 ------Lecythidaceae Uya-oy Planchonia spectabilis Nest Height(m) - - - - 2 7 - 4-9

105

Appendices

Dulungan Tarictic Family Local name Scientific name Nest parameter N Mean SD Range N Mean SD Range GBH(cm) - - - - 2 150 - 137-163 Altitude(m) - - - - 2 375 - 300-450 Orientation - - - - 2 - - 50-50 Meliaceae Bulog(T) Azidaracha indica Nest Height(m) 7 11 3.1 5-15 1 3 - - Taba-aw(D) Aglaia sp. GBH(cm) 7 190 63.3 120-280 1 230 - - Altitude(m) 7 579 26.7 530-610 1 160 - - Orientation 7 - - 40-200 1 - - - Moraceae Dural-og(D) Ficus nota Nest Height(m) 1 8 - - 1 9 - - Lunok(T) Ficus sp. GBH(cm) 1 190 - - 1 243 - - Altitude(m) 1 550 - - 1 350 - - Orientation 1 - - - 1 - - - Myristicaceae Lagasi Horsfieldia ardisiifolia Nest Height(m) 3 9 3.5 5-11 - - - - GBH(cm) 3 457 250.6 168-602 - - - - Altitude(m) 3 587 23.1 560-600 - - - - Orientation 3 - - 330-340 - - - - Myrtaceae Bagilomboy Syzygium bordenii Nest Height(m) 2 8 - 5-11 2 7 - 6-8 GBH(cm) 2 193 - 146-240 2 209 - 197-220 Altitude(m) 2 575 - 520-630 2 530 - 510-550 Orientation 2 - - 80-125 2 - - 170-270

106

Appendices

Dulungan Tarictic Family Local name Scientific name Nest parameter N Mean SD Range N Mean SD Range Rubiaceae Kaluntingan Neonauclea vidalii Nest Height(m) - - - - 1 6 - - GBH(cm) - - - - 1 152 - - Altitude(m) - - - - 1 270 - - Orientation - - - - 1 - - - Baid Baid Nest Height(m) 5 10 2.4 6-12 - - - - GBH(cm) 5 246 43.3 174-280 - - - - Altitude(m) 5 546 69.5 470-600 - - - - Orientation 5 - - 68-348 - - - - Sapindaceae Gogo(T) Ganophyllum falcatum Nest Height(m) 1 11 2.1 - 2 8 - 3-12 Oyakya(T) Pometia pinnata GBH(cm) 1 150 42.6 - 2 239 - 190-287 Bugo(D) Lepisanthes fruticosa Altitude(m) 1 655 63.3 - 2 415 - 310-520 Orientation 1 - - - 2 - - 15-30 Sapotaceae Nato Palaquium sp. Nest Height(m) 2 10 - 6-14 - - - - GBH(cm) 2 179 - 172-186 - - - - Altitude(m) 2 500 - 410-590 - - - - Orientation 2 - - 40-90 - - - - Sterculiaceae Taluto Pterocymbium tinctorium Nest Height(m) 1 8 - - 1 6 - - GBH(cm) 1 224 - - 1 200 - - Altitude(m) 1 490 - - 1 220 - -

107

Appendices

Dulungan Tarictic Family Local name Scientific name Nest parameter N Mean SD Range N Mean SD Range Orientation 1 - - - 1 - - - Libtog Libtog Nest Height(m) 24 12 3.5 6-18 4 10 2.3 8-12 GBH(cm) 24 233 62.7 120-387 4 202 34.8 162-235 Altitude(m) 24 512 83.5 340-700 4 464 107.5 365-580 Orientation 24 40-350 4 10-355 Maganhop Maganhop Nest Height(m) 2 10 - 9-11 4 8 1.9 5-9 GBH(cm) 2 185 - 167-203 4 191 54.1 140-264 Altitude(m) 2 475 - 450-500 4 300 64.8 230-360 Orientation 2 90-170 4 - - 60-340 Other species Atay-atay (T), Duguan (D), Kalulot(D,T) Nest Height(m) 8 12 3.4 6-15 7 8 4.9 1-15 Lanipga(D), Luwgating(D), Mogis(D) GBH(cm) 8 202 45.1 151-269 7 251 56.9 172-323

Oropag (T), Salin-Urang(D2), Sibuyas(T) Altitude(m) 8 488 93.5 310-590 7 499 94.1 340-600 Tamuyo(D), Tapoyay(T), Tul-ang(T), Yabot(T) Orientation 8 30-308 7 - - 10-240

108

Appendices

App. 3. Orientation (from true north) of entrance of nest holes occupied by the Dulungan (the values are in percentages) during two breeding seasons Dulungan 2009 Dulungan 2010

)

g ofg Group

rientation Direction of nest of nest entrance Direction bearin Midpoint of angle Mean entrance Orientation nest holes (n=54) test (z) Rayleigh’s vector (r) length Mean test (p) Rayleigh’s of angle Mean entrance O nest holes (n=67) test (z) Rayleigh’s vector (r length Mean test (p) Rayleigh’s All nest 100% 100% (1-360) 113o 0.89 0.13 0.2

109

Appendices

App. 4. Orientation (from true north) of entrance of nest holes occupied by the Tarictic (the values are in percentages) during two breeding seasons Tarictic 2009 Tarictic 2010

(r) (r)

length length

Direction nest ofDirection entrance ofMidpoint Group bearing Meanof angle entrance orientation nest (n=24) holes Rayleigh’s test (z) Meanvector Rayleigh’s test (p) Meanof angle entrance orientation nest (n=35) holes Rayleigh’s test (z) Meanvector length Rayleigh’s test (p) All nest 100 100 (1-360) 113o 0.025 0.032 0.2

0.5 24o 0.70 0.20 0.2

0.5 holes (n=24) (n=35) 360o North 4o 29 6.40 0.96 <0.001 2o 34 10.64 0.94 <0.001 (316o -45o) 90o East 69o 17 3.50 0.94 <0.05 81o 23 6.72 0.92 <0.001 (46o -135o) 180o South 169o 33 7.33 0.96 <0.001 174o 23 6.59 0.91 <0.001 (136o -225o) 270o West 260o 21 4.53 0.95 <0.01 264o 20 5.75 0.91 <0.001 (226o -315o)

110

Appendices

App. 5. Measurements of food overlap between nearest breeding pairs of the Dulungan during the 2009 breeding season Distance between Fruit species consumed Fruit species Overlap (%) nearest breeding pairs Breeding pair-1 Breeding pair-2 shared (m) 11 8 16 5 42 26 3 10 5 77 29 4 6 3 60 29 6 4 3 60 31 14 8 3 27 36 3 3 3 100 44 5 9 2 29 108 11 9 6 60 134 6 6 3 50 162 5 3 0 0 166 6 16 3 27 250 5 4 2 44 260 5 3 1 25

App. 6. Measurements of food overlap between nearest breeding pairs of the Dulungan during the breeding season 2010 Distance between Fruit species consumed by Fruit species Overlap nearest breeding pairs Breeding pair-1 Breeding pair-2 shared (%) (m) 18 10 5 3 40 33 5 7 4 67 44 11 7 4 44 52 17 13 6 40 58 9 7 3 38 62 10 10 3 30 62 13 13 5 38 76 4 8 3 50 77 5 6 2 36 80 10 8 5 56 83 2 8 1 20 89 6 9 3 40 94 6 4 2 40 97 13 13 5 38

111

Appendices

115 9 10 3 32 120 7 4 1 18 127 2 6 0 0 142 10 4 3 43 144 5 7 2 33 162 6 7 6 92 163 8 7 3 40 173 4 10 2 29 178 10 8 4 44 180 5 7 2 33 189 11 3 3 43 206 5 5 3 60 224 5 7 2 33 235 7 6 1 15 265 6 5 2 36 281 5 11 2 25 327 6 11 3 35 352 4 5 0 0 406 5 10 1 13 411 8 5 2 31 421 10 8 2 22 713 6 2 0 0

App. 7. Measurements of food overlap between nearest breeding pairs of the Tarictic during the 2009 breeding season Distance between Fruit species consumed Fruit species Overlap (%) nearest breeding pairs Breeding pair-1 Breeding pair-2 Shared (m) 0.5 5 5 100 5 23 13 11 4 33 39 3 6 1 22 61 2 5 1 29 78 3 3 2 67 111 5 11 3 38 128 2 13 2 27 484 4 5 1 22 112

Appendices

App. 8. Measurements of food overlap between nearest breeding pairs of the Tarictic during the breeding season 2010 Distance between Fruit species consumed Fruit species Overlap (%) nearest breeding pairs Breeding pair-1 Breeding pair-2 shared (m) 18 7 7 4 57 69 3 7 2 40 111 7 9 4 50 393 6 5 3 55 469 4 7 2 36

App. 9. Interspecific measurements of food overlap between nearest breeding pairs of the Dulungan and Tarictic during the 2009 breeding season Distance between Fruit species consumed Fruit species Overlap (%) nearest breeding pairs Tarictic Dulungan shared (m) 36 5 9 3 43 79 11 9 4 40 174 4 6 3 60 181 2 6 1 25 327 2 5 0 0 379 5 5 0 0 379 5 5 0 0 685 4 3 1 29 1447 3 3 1 33

App. 10. Interspecific measurements of food overlap between nearest breeding pairs of the Dulungan and Tarictic during the 2010 breeding season Distance between Fruit species consumed Fruit species Overlap (%) nearest breeding pairs Tarictic Dulungan shared (m) 19 2 3 0 0 30 9 5 2 29 36 7 7 1 14 36 7 3 0 0 78 5 7 1 17 84 5 5 1 20 143 7 3 1 20

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Appendices

181 7 8 2 27 373 7 3 0 0 486 8 3 2 36 539 4 6 0 0 539 3 3 1 33 791 7 6 1 15 1057 6 6 0 0 1486 3 3 0 0

App. 11. An account of direct observation of the Tarictic hornbill during the breeding season In addition to seeds collected from Tarictic broods, food data were also collected by direct observation during two breeding seasons. Out of three broods, one could be successfully habituated for obtaining food data. A total of 52 hours was spent during five days of observation during fledging of a Tarictic brood. A total of 757 food items were delivered by the male during 39 visits. The feeding started as early as 6:36hr a.m. to as late as 18:03hr p.m. in the evening. The diet was composed of 97.5% of fruits and 2.5% of animal food (only number of food items was considered). Six fruit species were supplied during the observation period, most frequently Platea excelsa (Bakan). Some fruits, fallen down during feeding, were collected and later on identified. The highest number fed in one run was unidentified reddish blue fruits, the fruits offered during this period were mostly black, red, orange, reddish blue, and purple coloured. Usually at a time, the fruits of single species were fed or sometimes with animal food. The animal food consisted of grasshoppers, beetles, flies, lizards and unidentified insects. The male, sometimes faced difficulty in regurgitating animal food, consequently would fly back to regurgitate remaining food on nearby branches. The mean number of visits and mean number of food items per day was 9.8±3.4 (mean±SD, n=4) and 189±97.6 (mean±SD, n=4), respectively. The mean number of food items per visit was recorded as 19.4±17.0 (mean±SD, n=39). During the whole observation period, 66.7% (n=26) of feeding visits contained only fruits and 18% (n=7) contained both fruits and animal food, while during the rest of feeding visits (15%, n=6) only animal food was delivered. A detailed account on direct observation of Tarictic brood is given below.

114

Appendices

Direct observations of Tarictic hornbill breeding pairs

During two breeding seasons, three Tarictic breeding pairs were selected for direct observation on their feeding and other behaviour. Out of three broods one was observed during the incubation period, another one during the nestling period and a third brood was observed during fledging. A detailed account of these observations is as follows:

A Tarictic nest hole containing three nestlings was observed from 16-06 to 22-06-2009 in the area of Barangay Calabanog (11 40.858 N 122 08.210 E), Municipality of Pandan. The nest hole was situated 14m above ground in a Balakbakan tree. A hide was placed 25m away from the nest tree. The male visited a tree close to the focal nest tree but did not approach or deliver any food, probably due to the newly placed hide in the vicinity. The male could not be habituated even after 6 days. The male would visit the area, flying over the hide while giving alarm calls. Sometimes he was accompanied by a group of other Tarictics, uttering loud alarm calls when bunching above the hide. This failure of habituating the male was probably due to the unsuitability of the hide, however, there was no alternate place suitable for making observations, hence, the observation was stopped.

Direct observations were made of another nest hole of the Tarictic in the area of Malumpati (11o 46.142′ N, 122o 04.229′ E) from 04 to 08 April 2010. The nest hole was reported to have been occupied on March 20, 2010. The nest tree was located at an elevation of 150m asl, at a height of 8m above ground with the opening oriented to SW (192o).

The hole was not directly visible but covered by branches, adventitious roots and ferns (Plate 3.5). The observations were taken between dawn (530hr) and dusk (1800hr), using a Leitz Televid 20-60X77 spotting scope, from a hide constructed of foliated branches at a distance of about 30m from the nest hole (Plate 3.10).

On the first day, the observation started in the afternoon. But the male did not visit the nest hole, probably due to the newly constructed hide. This behaviour indicates that the bird was very vigilant, shy, and wary, not approaching the nest hole to keep it concealed.

On the second day, April 5, no activity was observed from dawn to afternoon, however at 1537hr the male bird visited the nest hole. It did not visit the hole directly; instead approached it in short flights while calling from a distant tree and hopping closer from branch to branch and finally approaching the nest hole. The male was very vigilant while scanning the environs (Plate 3.7) and then turned to the hole and began cleaning it by 115

Appendices removing and throwing down some material from the nest hole. This activity lasted until 1600hr after that the male disappeared from the area and returned after half an hour at 1630hr along with a female Tarictic (Plate 3.8), and started calling from a nearby tree. First the male approached the nest hole and started peeping into it for only 5 min. After half an hour (1705hr) the female visited the hole and started investigating by peeping inside the nest hole. Then she started cleaning and removing some material from the hole that she dropped (Plate 3.9). Her ‘session’ lasted for 15 min, after that both left the area.

On the third day, April 6, the male visited at 1500hr, uttered some repeatedly loud calls from a nearby nest tree and after 5 min left the area, and reappeared at 1543hr and visited the focal nest hole. He looked inside the hole for about 3 min, moved swiftly from branch to branch, and left the area. On the following two days of observation no activity occurred. This long period of inactivity and the female visiting the nest, raised the question whether that was a helping female or the breeding female herself. It was supposed that the latter female was not inside the hole as indicated by a long period of inactivity and no delivery of food to the nest by the male.

This enigma was to be resolved only by checking if the breeding female was inside the hole. The nest hole when climbed was discovered to contain three eggs but the hole was still open (not sealed), however, it was concealed by adventitious roots and branches (Plate 3.5).

Observations of a Tarictic brood during fledging

Observations of a Tarictic brood were made in the Kabuluan area (11o 39.820′N, 122o 07.881′E) of Barangay Calabanog from June 14-18, 2010, to gather data on feeding, behaviour, nestling activities and fledging. The nest tree was located at an elevation of 270m asl, the hole at a height of 12m above ground with the opening oriented to East (100o).

The hole with a narrow elongated opening was in a strong branch and was open/ unsealed; the female had already left the nest hole, leaving behind a male and a female nestling. A hide/blind was constructed from branches with leaves at a distance of about 20m from the hole (Plate 3.10). The observations were running from dawn (0515hr) to dusk (1815hr) to cover the whole activity period. Incidentally the observations covered the last five days of the breeding cycle, giving some insight into fledging.

116

Appendices

On June 14, during the first visit, the male started alarm calling and flew many times over the hide and was still reluctant to visit the nest hole. However, it habituated to the new structure surprisingly fast, probably due to the fact that the nest hole tree was in the agricultural land where Tarictics were used to human activities. The male revisited the area about two hours after the first visit and delivered 7 fruits of one species. During the rest of the day from 1219hr to 1741hr a total of 7 visits was made to the nest, during which time 116 fruits from 2 plant species and animal food were delivered four times. The animal food was delivered along with fruits or on separate visits. The fruits were mostly regurgitated singly but sometimes two or three fruits were regurgitated at a time, however, they were fed singly. During feeding some fruits would also drop beneath the nest hole, and later on could thus be identified. In one run the fruits of a single species were delivered, or sometimes with insects. Usually the first food item was regurgitated on a nearby branch before approaching the nest hole (Plate 3.11). Sometimes the fruits were fed to the nestlings in two runs whereby after feeding some fruits the male flew back to the branch and then approached the hole again to feed the rest. When the male would approach a nearby branch, uttering a short call, the nestlings would start begging for food by screaming.

On June 15, the first and second visit made by the male was at 0600hr and 0630hr, during both visits the male only called from nearby branches. On his approaching the nestlings responded by screaming. At 0700hr both male and female visited the nest hole but no food was provided, again at 0705hr only the female visited the nest but again without providing food. At 0710hr the male visited the hole and provided 38 fruits while the female was calling from nearby branches. From this time onward a total of 17 visits were made to the nest hole, of which four visits went food-free. The male’s feeding occurred at 1801hr, and then stopped. The fruits provided in one run ranged from 2 to 48 and 6 items of animal food were also provided. During regurgitating animal food, the male had sometimes difficulty in regurgitating one after the other, he would fly back to nearby branches to regurgitate the food and would again visit the nest hole to provide the rest of the food. At 1640hr male and female visited the nest but no food was provided. While visiting the nest the male started waggling his head and left without providing food to the nestlings.

On June 16, both male and female made their first visits to the area at 0538hr, calling from nearby trees. The second visit was made 0626hr by the female who looked into the 117

Appendices hole and put her beak into the hole as if she was offering food to the nestlings, but in fact had nothing in her bill to offer. After 10 min the male started feeding and delivered 22 fruits. The last visit was made at 1539hr during which 59 fruits were fed to the chicks, which is the highest number observed during the whole period of observation.

During 11 visits 278 fruits belonging to four species and one insect were provided to the nestlings. During one visit the male provided fruits, after taking 4 fruits the chicks refused further offerings and the male left the nest hole with fruits in his bill. On this day at 0828hr the male nestling for the first time exposed himself to the outside and scanned the environs carefully. The nestlings were observed cleaning the hole, throwing down seeds and feathers, also cleaning the front of the opening from faeces, while stretching and flapping their wings at the entrance.

On June 17, at 0544hr, nestlings started calling inside the hole. The male chick (appeared in front of the opening and) started looking outside the hole (Plate 3.12). After scanning the area he started squeezing through the hole. First head, then right wing, then right leg and then the other body parts were squeezed through the opening. The male chick fledged at 0548hr. During fledging, the parents were observing from nearby branches and on fledging, the male accompanied the fledgling. Soon after fledging, the female visited the nest at 0650hr and after looking into the hole flew back immediately. The male provided to the remaining female chick only three fruits at 0653hr. Seven visits were made by the male during which 77 fruits and 3 insects were fed. During some feeding visits, the only chick remaining did not accept the food and the male swallowed the regurgitated fruits and flew back from the nest hole, and sometimes visited the nest without feeding while withholding the food. When the chick became hungry it would scream.

On June 18, at 0515hr the female nestling started stretching and flapping her wings inside the nest hole. At 0535hr she started calling, looking out of the opening (Plate 12). At 0605hr the male visited the area and uttered calls, the female nestling responded by screaming, but no food was provided. At 0633hr the chick fledged, repeating the same behavioural sequences as the male chick had been doing. First head, then right wing, then right leg and then the other parts of the body were squeezed through the opening (Plate 3.13) in the presence of the adult male. Another Tarictic nest hole (11o 40.146′ N, 122o 08.059′ E) was located in a Toog tree at an elevation of 370m, less than 1m high from the ground. The brood had fledged on June 15, 2010.

118

cknowledgements

Acknowledgements

I would like to express my deep gratitude to my supervisor, Prof. Dr. Eberhard Curio, for his expert opinion, guidelines, and his critical views throughout my study period. I am sure it would not have been possible without his involvement to bring this dissertation into its present shape. I am truly indebted and thankful to my co-supervisor, Prof. Dr. Ralph Tollrian for his invaluable suggestions to improve my dissertation. His cooperation and kind behaviour during my study will last longer in my memory. To complete my doctoral study, I am deeply in debt to the University of Azad Jammu and Kashmir, Muzaffarabad, Pakistan, for a fully funded scholarship over the whole study period. I cannot remain without mentioning the name of Prof. Dr. Khawaja-Farooq-Ahmad, who nurtured my thinking in the right direction. I am sincerely thankful for his timely guidance, instructions, and support in pursuing my higher studies. My thanks are to Maria Theresa Ibabao and Thomas Künzel for their cooperation during my stay in the Philippines. I am obliged to all PESCP staff members, forest rangers and all local nest owners, porters and guides who have been all the time with me during field surveys. It would have been impossible to conduct field surveys without their cooperation and involvement I owe my thanks to Honorio Jamandron and Alexander Alabado for arranging field trips, Ebon Armelito, Jose Matinong, Martin Berg, and Freddie for field assistance, Jun Tacud for fruit/seed and seedling identification and Svenja Sammler for hornbill identification at species the level by DNA analysis. I extend my sincere thanks to Mudaser Iqbal for tackling my matters in Germany, especially in my absence during fieldwork. I am thankful to Mr. Tahir Mughal, Imaran Ghumman, Azhar Butt, Hafiz Ahmad, Mahmood-al-Hassan and all other colleagues at Dortmund for their nice company that compensated for my loneliness and homesickness. I extend my gratitude to my brothers Ashfaq Ahmad, Iftikhar Ahamad and Mudassar Hussain, and all those who did not let my family suffer in my absence, and accomplished the responsibility of taking care of them for such a long period. Finally yet importantly, I am highly indebted to my parents who were in dire need of my support at the old stage of their life, and whose prayers remained a source of strength throughout my life in pursuing my goal. I believe that this dissertation is an accomplishment at the cost of my family, for which I am deeply thankful for the endurance of my wife, Iffat, and the children Danish and Aisha, whom I could not take care of as efficiently as the male hornbill uses to do for his family.

119

Declaration

Erklärung

Hiermit erkläre ich, dass ich die Arbeit selbstständig verfasst und bei keiner anderen Fakultät eingereicht und dass ich keine anderen als die angegebenen Hilfsmittel verwendet habe. Es handelt sich bei der heute von mir eingereichten Dissertation um sechs in Wort und Bild völlig übereinstimmende Exemplare. Weiterhin erkläre ich, dass digitale Abbildungen nur die originalen Daten enthalten und in keinem Fall inhaltsverändernde Bildbearbeitung vorgenommen wurde.

Bochum, den 18.01.2013

______Basharat Ahmad

120

Curriculum Vitae

Curriculum Vitae

NAME: BASHARAT AHMAD PERSONAL DETAILS: Permanent Address: Correspondence Address: Gulshan Colony, ward no.13 Assistant Professor, Department of Zoology Eidgah Road Muzaffarabad University of Azad Jammu & Kashmir Azad Kashmir PAKISTAN Muzaffarabad, PAKISTAN E-Mail: [email protected]

Date of Birth: 28 April 1972 Nationality: Kashmiri (Pakistan) EDUCATION:

Duration Qualification Institution attended

2004 M.Phil Zoology AJ&K University MZD

1999 M.Sc.Zoology AJ&K University MZD

1994 B.Sc. (Zoology, Botany, Chemistry) AJ&K University MZD SERVICE/TEACHING EXPERIENCE: i) Working as Assistant Professor at the Department of Zoology, From 2008-todate University of Azad Jammu and Kashmir ii) Worked as Lecturer Zoology at the Department of Zoology, From 2004-2008 University of Azad Jammu and Kashmir iii) Worked as Research Associate in the PSF funded project No. From 2003 to 2006 AJK/UCR/BIO (333) entitled “Distribution, Population Status and Conservation of Cheer Pheasant (Catreus wallichii) in Jhelum Valley, Muzaffarabad, Azad Kashmir, Pakistan iv) Worked as Teaching Assistant at the Department of Zoology From 2001 to 2002 University of Azad Jammu & Kashmir. I had been teaching a course

of “Zoogeography” to M.Sc. final year class. ______RESEARCH EXPERIENCE: i) Working experience as Research Associate in the project entitled “Distribution and Conservation of Cheer Pheasant (Catreus wallichii) in Jhellum Valley, Azad Kashmir, Pakistan” ii) Thesis (M. Phill) Zoology: “Biology, Status and Habitat Relations of Asiatic Jackal (Canis aureus aureus) in Arable Biomes of Central Punjab”. iii) Thesis (M.Sc.) Zoology: “Status of Major Wildlife Species and their Management in the Moji Game Reserve, Leepa Valley, Muzaffarabad, Azad Kashmir”.

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Curriculum Vitae

STUDENTS SUPERVISED (M.Phil. Student) i) Biology of Himalayan Grey Langur (Semnopithecus entellus ajex Pocock, 1928) in Machiara National Park, Muzaffarabad Azad Kashmir (Pakistan) (Riaz Aziz Minhas: Session 2006-2008).

(MSc. Student) ii) Preliminary study on distribution and population of avian fauna in and around Trarkhal City, district Sudhnuti Azad Kashmir (By Rehana Bashir: Session 2005-2007). iii) Baseline study of Bird Diversity of Pir Lasorha National Park, district Kotli, Azad Jammu and Kashmir (By Nuzhat Batool: Session 2005-2007). iv) Distribution and population status of avian faua of Paniola City, district Poonch Azad Jammu and Kashmir (By Gulnaz Iltaf: Session 2005-2007). v) Distribution of Small Mammals in Bannigala Hills Islamabad (By Shazia Azam: Session 2004-2006). vi) Distribution, Population Status and Habitat Preferences of Avian Fauna at NARC, Islamabad (By Zaheen Akhtar: Session 2004-2006). vii) Distribution and Abundance of Rat and Mice Burrows in Different Agricultural Crops at NARC (By Saira Begam: Session 2002-2004). viii) Distribution, Population Status and Habitat Preferences of Avian Fauna of Rawal Lake of Islamabad (By Rehana Farooq: Session 2004-2006). ix) Distribution, Habitat utilization and Population Estimation of Common Otter (Lutra lutra) in River Neelum, District Neelum Azad Kashmir (By Muhammad Bashir Khan). x) Distribution Population Status and Habitat Utilization of Himalayan Ibex (Capra ibex sibirica) in Upper Neelum Valley District Neelum Azad Kashmir (By Usman Ali). xi) Distribution, Population Status and Habitat Preferences of Avian Fauna of Rawalakot City Azad Kashmir (By Shagufta Naz: Session 2001-2003). xii) Distribution, Status and Habitat Utilization of Alectoris Chukar in Machiara Nationl Park District Muzaffarabad Azad Kashmir (By Mir Muhamad Saleem: Session 2001-2003). RESEARCH PUBLICATIONS: 1. Khan, M.B., Ahmed, K.B., Awan, M.S., Ali, U., Minhas, R.A., and Choudary, S.A. 2012. Distribution, population status and habitat utilization of Common Otter (Lutra lutra) in Neelum Valley, Azad Jammu and Kashmir. Pakistan J. Zool. 44(1): 233-239.

2. Minhas, R.A., Ahmed, K.B., Awan, M.S., Zaman, Q., Dar N.I., and Ali, H. 2012. Distribution Patterns and Population Status of the Himalayan GreyLangur (Semnopithecus ajax) in Machiara National Park, Azad Jammu and Kashmir, Pakistan. Pakistan J. Zool., vol. 44(3): 869-877, 2012.

3. Minhas, R.A., Awan, M.S.and Ahmad, K.B. 2010. Social Organization and Reproductive Biology of Himalayan Grey Langur (Semnopithecus entellus ajex) in Machiara National Park, Azad Kashmir (Pakistan). Pakistan J. Zool., 42(2):143-156.

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Curriculum Vitae

4. Minhas, R..A., Ahmed, K.B., Awan, M.S. and Dar, N.I. 2010. Habitat Utilization and Feeding Biology of Himalayan Grey Langur (Semnopithecus entellus ajex) in Machiara National Park Azad Kashmir (Pakistan). Zool. Res. 31(2):177-188.

5. Ali, U., Ahmad, K.B.,Awa, M.S., Aashraf, S., Bashir, B. and Awan, M.N. 2007. Current Distribution and Status of Himalayan Ibex in Upper Neelum Valley, District Neelum Azad Kashmir, Pakistan. P.J.Bio. Sci. 10 (18): 3150-3153.

6. Awan, M. N., Saleem, M.M., Awan M. S. and Ahmed, K.B. 2007. Distribution, Status and Habitat Utilization of Alectris chukar in Machiara National Park, District Muzaffarabad, Azad Kashmir. J. Agri. Soc. Sci. 2(4): 230-233

7. Khan, A.S., Awan, M.S., Ahmed, K. B. and Dar, N.I. 2006. Distribution and population status of Cheer Pheasant (Catreus wallichii) in Phalla Game Reserve, District Bagh, Azad Jammu and Kashmir, Pakistan. Pak. J. Biol. Sci. 9(5): 810-815.

8. Awan, M. S., Khan, A.A., Ahmed K. B., Qureshi, M.A., Malik, M. A. and Dar. N. I. 2004. Population Dynamics of Cheer Pheasant (Catreus wallichii) in Jhelum Valley, Muzaffarabad, Azad Kashmir, Pakistan. Pak. J. Biol. Sci., 7 (5): 789-796.

9. Awan, M. S., Khan, A. A., Qureshi, M. A., Ahmed, K. B. and Murtaza, G. 2004. Habitat Utilization of Cheer Pheasant (Catreus wallichii) in Jhelum Valley, Muzaffarabad, Azad Kashmir, Pakistan. Pak. J. Applied Sci., 4 (2): 250-256.

10. Awan, M. S., Khan, A. A., Ahmed K. B., Qureshi, M. A. and Dar. N. I. 2004. First Breeding and Nidification Record of Cheer Pheasant (Catreus wallichii) in Jhelum Valley, Muzaffarabad, Azad Kashmir, Pakistan. J. Biol . Sci. 4 (3): 304-308.

11. Awan, M. S., Minhas. R. A. and Ahmed K. B. 2004. Distribution, Food and Habitat Preferences of Small Mammals in Machiara National Park, District Muzaffarabad, Azad Kashmir. Punjab Univ. J. Zool. 19: 17-31.

12. Awan, M. N., Awan, M. S., Ahmed K. B., Khan, A. A. and Dar, N. I. 2004. A Preliminary Study on Distribution of Avian Fauna of Muzaffarabad-Azad Jammu and Kashmir, Pakistan. Int. J. Agri. Biol. 6 (2): 300-302.

13. Hussain, R. and Ahmed, K. B. 2004. The Description of the Naiads of Orthetrum, Trithemis and Sympetrum (Odonata: Libellulidae) from Sindh Province). Pak. J. Bio. Sci. 7(3):419-422.

14. Hussain, R. and Ahmed, K. B. 2003 Damselfly Naiads (Odonata: Zygoptera) of Sindh- Pakistan. Int. J.Agri. Biol.5 (1): 53-56.

15. Ahmed, K. B., Awan, M. S. and Anwar, M. 1999. Status of Major Wildlife Species in the Moji Game Reserve, Leepa Valley, Azad Kashmir.Proc. Pakistan Congr. Zool. 19: 173- 182.

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