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Senckenbergiana biologica | 86 | 1 | 109­–125 | 4 figs., 2 tabs. | Frankfurt am Main, 15. vi. 2006

Population numbers and status of land birds of the Juan Fernández Archipelago, Chile (Aves: Falconiformes, Columbiformes, Strigiformes, Caprimulgiformes, Passeriformes)

Ingo Hahn, Uwe Römer & Roberto P. Schlatter

Abstract

Results of a recent land bird population survey of the Juan Fernandez Archipelago are pre- sented. To additionally gain indications for possible tendencies, two censuses with a seven year interval were carried out (19­9­4/9­5 and 2001/02). During the 111 line transect counts 249­6 bird records were made, covering the eleven resident species and the three islands (Robinson Crusoe, Alejandro Selkirk, Santa Clara). On base of this total bird numbers were calculated, including ad- ditional data of distribution and ecology, for each island, habitat type, and species. For the entire archipelago (9­380 ha) in 2001/02 a total of 15 175 land bird specimens is calculated (1.62 ind./ha). Non-endemics were more abundant than endemics (63:37%). Robinson Crusoe shows the highest overall land bird density (2.56 ind./ha), however, mainly basing on non-endemics (70%). Contra- rily Alejandro Selkirk hosts much lower individual numbers (0.65/ha), but endemics take a higher proportion on the overall land bird community (65%). Three of the endemic taxa possess very low total population sizes: Falco sparverius fernandensis, Sephanoides fernandensis, and especially Aphrastura masafuerae with only about 140 individuals. Although differences between the two study periods generally may be related to natural fluctuations, the populations of the mentioned taxa probably have suffered strong decline since human impact began in 1574. Alteration of habi- tats, introduction of predators, and immigration of competitive birds seem to be the main threats

for these endemics. Basing on theseeschweizerbartxxx sng-results, the archipelago represents not only the most important endemic bird area of Chile and in the south-east Pacific Ocean, but also the most threatened one including several endangered endemics. Conservation management should include monitoring of the bird populations, basic research of their ecology (especially reproduction), and removal of introduced (plant and animal) species. Eradication campaigns should start with goats on Alejandro Selkirk, rabbits on Santa Clara, and cats in Robinson Crusoe’s settlement. K e y w o r d s : Alejandro Selkirk, biosphere reserve, island birds, bird census, bird habitats, endangered species, national park, nature conservation, Robinson Crusoe, transect method.

Números poblacionales y estatus de las aves terrestres del Archipiélago de Juan Fernández, Chile (Aves: Falconiformes, Columbiformes, Strigiformes, Caprimulgiformes, Passeriformes)

R e s u m e n : Se dan a presentar resultados de un estudio poblacional de las aves terrestres del Archipiélago de Juan Fernández. Para adicionalmente ganar indicaciones de tendencias, dos censos han sido realizado con un intervalo de siete anos (19­9­4/9­5 y 2001/2002). 249­6 contactos de aves han sido registrado en las 111 transectos lineares, cubriendo las once especies residentes y las tres islas (Robinsón Crusoe, Alejandro Selkirk, Santa Clara). Con esa base números totales de aves han sido calculado, incluyendo datos adicionales de distribución e ecología, para cada isla, tipo de hábitat, e especie. Para el archipiélago entero (9­380 ha) en 2001/02 un total de 15 175 especimenes de aves

Dr. Ingo Hahn, Departamento de Ecología, Pontificia Univ. Católica de Chile, Casilla 114-D, Santiago, Chile. — Current address: Institute of Landscape Ecology, Robert-Koch-Strasse 26, D-48149­ Münster, Germany; [email protected] Dr. Uwe Römer, Faculty of Biology, Universität Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany; [email protected] Prof. Dr. Roberto P. Schlatter, Instituto de Zoología “Ernst F. Kilian”, Facultad de Ciencias, Universidad Austral de Chile, Ca- silla 567, Valdivia, Chile; [email protected]

© E. Schweizerbart’sche Verlagsbuchhandlung (Nägele u. Obermiller), 2006, ISSN 0037-2102 110

terrestres han sido calculado (1,62 ind./ha). Non-endémicos estaban mas abundante que endémicos (63:37%). Robinsón Crusoe tiene la densidad total mas alta de aves terrestres (2,56 ind./ha), pero mayoramente por base de non-endémicos (70%). En contraposición Alejandro Selkirk hospedas números de individuos mucho mas bajos (0,65/ha), pero endémicos toman una porción mas grande de la comunidad total de aves terrestres (65%). Tres de los taxa endémicos tienen poblaciones totales muy bajas: Falco sparverius fernandensis, Sephanoides fernandensis, y especialmente Aphrastura masafuerae con solo 140 individuos. Aunque las diferencias de los dos periodos de investigación posiblemente están en relación con fluctuaciones naturales, las poblaciones de las tres formas mencionadas probablemente han sido sufriendo disminuciones fuertes desde el inicio del impacto humano en 1574. Alteración de hábitat, introducción de predadores, e invasión de aves competitivos probablemente representan los grandes peligros para esos endémicos. Basando en esos resultados, el Archipiélago de Juan Fernández no solamente representa el área mas impor- tante para aves endémicos en Chile y en el sureste del Océano Pacifico, pero también el área mas en peligro incluyendo varias especies endémicas. Manejo de conservación debe incluir monitorio de las poblaciones des aves, estudios básicos de su ecología (especialmente reproducción), y la erradicación de especies introducidos (de plantas e animales). Programas de erradicación deben enseñar con cabras en Alejandro Selkirk, conejos en Santa Clara, y gatos en la población humana de Robinsón Crusoe.

Introduction

Although islands cover only about 2% of the terres- special conservation threats. Indeed, all endemic land bird trial surface, they host an important part of the global taxa of the archipelago are principally threatened (Glade biodiversity: for instance 14% of all mammal species 1993): the superficies is very limited, massive habitat al- (Alcover et al. 19­9­8) and more than 30% of several bird teration has been detected, and preliminary observations families (Clements 2000). Islands became known as indicate low abundances. For single species a high extinc- speciation centres and, in geographical isolation, large tion risk already has been expected (Brooke 1987, Bourne numbers of endemic species evolved (Johnson eschweizerbartxxx& sng- Stat- et al. 19­9­2, Hahn & Römer 1996, Roy et al. 19­9­9­). tersfield 19­9­0). Birds are especially well represented on However, still little is known about the populations islands, as they are favoured to reach them through their of the islands’ avifauna. One species, the Juan Fernan- ability to fly. dez Firecrown (Sephanoides fernandensis (King 1830), However, naturally most islands are of small size, of- Caprimulgiformes, Trochilidae), already has been stud- fering only very limited potential for distribution, and do ied and counted (although quite some time ago). Most not provide many retreat areas for their bird species. But land bird species only have been estimated roughly with- it was theoretically speculated that island birds generally out method, others never been in the focus of quantita- possess higher population densities than their mainland tive registration at all. But the basis for any successful pendants, mostly because species richness was detected conservation management is the knowledge of reliable to be lower (MacArthur & Wilson 19­67, MacArthur population numbers. Thus, census covering as many et al. 19­72). Practically it turned out that human impact individuals as possible of the total island population has highly severe consequences for island ecosystems: becomes necessary. For comparing and detecting spe- many of the autochthonous island populations of previ- cies of special conservation concern, generally all land ously abundant bird species strongly declined and now bird species need to be included into census programs. are threatened (Collar et al. 19­9­4, Stattersfield & Cap- This would also lead to results of basic scientific interest per 2000) or have already become extinct through this which, in turn, might be of significance for practical con- influence (Diamond 19­82, King 19­80, 19­85). About two servation action. For example it is not known, to which thirds of all recently threatened bird species live on is- extent autochthonous and allochthonous habitat types lands and amongst 217 extinct bird taxa worldwide, 200 are inhabited by endemic birds on the one hand, and by had been restricted to islands (Imboden 19­85). non-endemics on the other hand. Differences in regard In Chile about 50% of the endemic avifauna is re- to entire islands, island regions, or habitat types may be stricted to a number of small islands (especially Juan detected. On the Juan Fernandez Islands this might bring Fernandez), which cover less than 1% of the county’s insight in differentiation of the two main islands, Rob- surface (Araya et al. 19­9­5, compare also Stattersfield et inson Crusoe and Alejandro Selkirk, which show about al. 19­9­8). Thus, these islands are of overwhelming impor- the same superficies and geographical latitude, but are tance for the country’s endemic avifauna, but might face separated by a sea distance of ca. 170 km. 111

Through comparative repetition after several years, alpine vegetation is found. The islands belong to the few especially if including identical investigators, methods, places that remained untouched by man until the discov- and sample plots, it would become possible to gain in- ery by European sailors (1574): the Polynesians did not formation of population tendencies. Such information reach further than Easter Island and the Native Americans would be crucial indicator to detect critical species and stayed on the South American continent. help to manage them at an earlier state. As birds repre- Compared to others, the Juan Fernandez Archipelago sent the only native terrestrial vertebrates of the archi- is characterised by a high number and proportion of en- pelago, such census would be essential to create a more demics: Sohmer (pers. com. to Stuessy 19­9­2) states that complete conservation program. At the time preservation its number of endemic plant species per area unit is the and/or reconstruction demands of the Juan Fernandez highest of all oceanic island systems. The flora contains island ecosystem are mainly based on a floristic back- at least 127 endemic species, eleven endemic genera ground (Skottsberg 1953, Stuessy 1992, Sanders et and one endemic family (cf. Stuessy 1992, Ricci 1992, al. 19­84, Stuessy & Ono 19­9­8). With the results of our Danton et al. 19­9­9­). Most endemic species of the Juan study presented in the following it will be possible to put Fernández Archipelago show relations to southern South it on a quantitative faunistic background too. America or about 80% of the vascular plants. 10% have their origin in the West Pacific (e.g. New Zealand, Aus- tralia), 7% have immigrated from the Neotropics, and Study area and biogeographic background about 3% originate from more distant regions (Stuessy 19­9­2). The diasporas were probably primarily trans- The volcanic Juan Fernández Islands are located in ported to the islands by birds (Skottsberg 1928, 1953, the south-east Pacific Ocean off the coast of Chile, to Stuessy 19­9­2). which it politically belongs. The archipelago stretches The archipelago’s biogeographic isolation and high from 33°28'48" to 33°47'57" South and from 78°47'12" degree of nativity is also reflected by the birds’ ende- to 80°47'44" West, and consists of the islands Isla Robin- mism rate: amongst the 310 breeding bird species of son Crusoe (formerly Másatierra), Isla Alejandro Selkirk Chile (Araya et al. 19­9­5), only 15 are endemic species. (formerly Másafuera), Isla Santa Clara, and some small However, amongst the 17 breeding bird species of the rocks. The easternmost Robinson Crusoe is 587 km dis- Juan Fernández Islands, five species and three subspe- tant from the South American continent. The western- cies are endemic (eight forms). Four additional species most Alejandro Selkirk is situated further 167 km west breed outside the archipelago on Mocha or Desventura- of Robinson Crusoe. The smaller Santa Clara is only das Islands only. Thus, the Juan Fernández Archipelago

1.5 km south-west of Robinson Crusoe. The areaeschweizerbartxxx sng- of Rob- is not only of major importance to the endemic avifauna inson Crusoe is 47.11 km², of Santa Clara 2.23 km², and of Chile but also of international interest and known of Alejandro Selkirk about 44.64 km². While Santa Clara as an Endemic Bird Area (EBA) (Stattersfield et al. is only 375 m high, the Yunque Mountain on Robinson 19­9­8, Wege & Long 19­9­5), a National Park (CONAF), Crusoe reaches 9­15 m. Alejandro Selkirk is 1333 m high a World Biosphere Reserve (UNSESCO), and was even (own data 2002) and summits in the Pico del Inocentes. categorised as one of worldwide 12 Natural Areas of The Juan Fernández Archipelago, with exception of the high conservation importance (Allen 19­84). San Juan Bautista settlement, is a Chilean national park Nevertheless, the islands meanwhile have suffered se- since 19­35, and also has, because of the international vere human impact in some areas. Already along with the value, the status of a Unesco Biosphere Reserve since discoverer Juan Fernández goats and pigs were brought 19­77. More detailed geographical descriptions may be to the archipelago (see also Daly & Goriup 19­87). High taken from Skottsberg (1920–1956), Castilla (19­87), goat numbers were reported throughout the 17th century and Stuessy & Ono (19­9­8). from Robinson Crusoe, until dogs were introduced re- The archipelago is located between Polynesia and ducing the goat population: at the time when Alexander South America. It is different from all others by a unique Selkirk — model of Daniel Defoe’s roman — lived on combination of environmental factors: neither entirely be- the island from 1704 to1709­, goats were less numerous. longing to the Neotropical flora nor to the Antarctic, but Other mammal species were introduced later on; herbiv- representing a separate floristic region (Blake & Atwood ores caused the destruction of vegetation and predators 1963, Morrone 2000). Various factors are responsible for the reduction of native bird life. However, up to now the archipelago’s biogeographic isolation and high ende- the only supposed extinct bird is the possible subspecies mism rate: lack of neighbouring islands within 500 km leyboldi of the Juan Fernández Firecrown (Gould 1870). radius, long distance to the mainland, the cool Humboldt This endemic hummingbird may have vanished from Current leading northward ashore the South American Alejandro Selkirk in the early 20th century, but there are continent, and the mostly southern and western winds. some reasonable doubts on the previous existence of this Because of the considerable altitude above sea-level, also form (Johow 2003). 112

Materials and methods called efficient if two thirds of the present birds are registered (Eberhardt 19­78), we aimed to register a significantly higher To investigate the islands’ birds and their populations, from portion by choosing a small width. This methodical adaptation 19­9­2 to 2002 four field campaigns were carried out on the Juan is especially suitable for island ecosystems where birds not Fernández Archipelago. All three major islands were visited react with intensive escaping flights or warning behaviour (Co- during a total of 29­9­ days (24. xi. 19­9­2–2. ii. 19­9­3, 24. iii.– nant et al. 19­81). For mainland censuses a greater line transect 13. iv. 19­9­4, 22. x. 19­9­4–13. ii. 19­9­5, 9­. xi. 2001–11. ii. 2002). width is often preferable, as the severer observer impact de- Habitat types and their vegetation structures were studied on creases along with the distance to the bird. During different base of structure analyses and vegetation relevees (Hahn 1998, phases of bird reproduction, different activity patterns may be 2000). For distribution maps of habitat types one may refer to found, including vocalisation (Hilden 19­81). To at least mini- Hahn (in press). mise the error that is caused by different vocal activities during Visual identification of birds was straight forward, using these periods, it was tried to record birds additionally by visual Araya et al. (19­9­2, see also Jaramillo 2003) and the original contact, for which a small transect width was favourable too. species descriptions. Acoustic identification was possible after It was only in a few cases possible to determine or check learning the bird vocalisations from observation and taping transect length on base of maps, as the present material was with a DAT-Recorder (Sony, HD-S100) (e.g. Hahn & Mattes of small scale and showed few trails. However, even in cases 2000). To estimate bird populations, numerous methods have where possible, the true distance was higher than the meas- been used during the past decades (overviews in Ralph & ured one, resulting from the immeasurable incline in the map. Scott 1981, Mühlenberg 1993, Bibby et al. 2000). Our abun- Therefore distances were mostly measured directly in the field dance data should reach a high level of inter-specific compara- by using a pedometer or indirectly by taking the time. If the bility and cover a maximum area. Therefore the line transect distance was calculated by taking the time, the walking speed method was chosen (description by Emlen 1971, 1977). was tested in advance on routes of known distance and/or ad- Basing on theoretical considerations, it was postulated that ditionally checked using the pedometer values. The walking line transect counts with multiple distance zones prepare more speed was adapted to the terrain conditions (habitat structure, accurate results than those with only one zone. However, prac- topography etc.). tical experiments showed that the results were not significantly The 2001/02 data serve as basis for calculating recent bird different (Franzreb 19­81). Moreover by choosing only one population sizes of habitat types and species. Details are given distance zone the error is minimised that derives from inexact in table 1 (49­ counts). The 19­9­2–9­5 data (62 counts) led to distance estimation and by the movements of birds between the population sizes presented in the figures (Figs. 1–4) for tem- distance zones. Thus, taking the habitat structure and the nar- poral comparisons. During the 2001/02 census, transect counts row transect width into account, the registration with only one were carried out in 14 of the 16 different habitat types (tab. 2). distance zone on each side of the centre line turned out to be In the habitat types 7 and 8 no count was carried out. Habitat most suitable. A critical comparison of some line transect vari- type 7 (Santa Clara) could not be visited during the last study ants is given by Tilghman & Rusch (19­81). Haila & Järvinen period, but census data are available from 19­9­4. Habitat type 8 eschweizerbartxxx sng- (19­81) give some general methodological assumptions on is- (montane laurel forests on Alejandro Selkirk) showed a highly land focused censuses. fragmented distribution pattern and small patch sizes, which The transect width was often small (tab. 1), to register also made it kind of unsuitable for transect counts. Additional ob- transect-peripheral individuals in partly dense vegetation with servations showed that these forests do not bear much bird life high probability. Although a quantitative method is already at all, contrarily to those of Robinson Crusoe.

Results

A total of 111 line transect counts was carried out last- Island and habitat relation ing 219­5 minutes, covering an area of 2227.584 hectares. Transect counts led through all altitudes from sea-level Adding up the 2001/02 population sizes of the eleven to the highest summit. During the counts 249­6 contacts land bird species, a total of 15,175 specimens results for with birds were recorded, covering all eleven resident the entire archipelago (9­380 ha), which would mean an land bird species of the archipelago. The highest spe- average of 1.62 specimens per hectare. However, dif- cies number during a single count was four, the highest ferences in abundance are significantly high between number of contacts with bird individuals was 63, and in islands and habitat types. Robinson Crusoe by far shows only one count no birds were observed. Transect area the highest absolute (12 075) and average (2.56/ha) num- was largest in habitat type 6 with 355 ha, but not num- bers amongst the three islands. Abundances reach values bers of bird contacts (150 ind.). Most birds (160 ind.) up to 15 individuals per hectare in the settlement area. were recorded in habitat type 1 on 27 ha (tab. 1). Only open terrain with some grasslands show values 113

Fig. 1: Habitat types of the Juan Fernandez Islands and their land bird densities derived from census counts in 2001/02. For de- scription of habitats refer to table 2. Numbers 1–6 belong to Robinson Crusoe, 9­a–12 belong to Alejandro Selkirk, 7 and 8 were not investigated. lower than 1 individual per ha. Contrarily, on Alejandro and the highest population sizes are recognised for the Selkirk low absolute (289­0) and average (0.65/ha) land non-endemics Austral Thrush and the Green-backed bird numbers are found. Here populations do not reach Firecrown. Although the census data from the two study abundances of more than 1 individual per haeschweizerbartxxx in sng- any type seasons are not sufficient to detect true trends or fluc- of habitat. Basing on data from the 19­9­4 census a total tuations, they may serve as indicators for population population of 210 land birds is calculated for small Santa tendencies. The overall tendency in population decline Clara. This is still a higher average (0.9­4/ha) than for the since 19­9­4/9­5 is present in numerous species, endemics open terrain habitats of Robinson Crusoe and Alejandro and non-endemics respectively, but the most abundant Selkirk (Fig. 1). species seem to have had strongest losses. Non-endem- Another difference between the two major islands is ics lost about 32.8% and endemics about 10.6% of their detected in the proportion of endemics in the overall bird total populations over a seven year period. Four out of community. On Robinson Crusoe all six habitat types are the six endemic land birds show negative tendencies dominated by non-endemic birds. Only in the autoch- in 2001/02, but three of them had already relative low thonous laurel forests endemics become more abundant populations in 19­9­4/9­5. Thus, an overall critical situation (nearly 50% of the individuals), but in all other habitats may be identified for endemic taxa in total. they are clearly subdominant (0–25%). The average pro- Másafuera Red-backed Hawks Buteo polyosoma ex- portion of endemics on this island is 30%. Contrarily on sul (Salvin 1875) (Falconiformes, Accipitridae) were Alejandro Selkirk 65% of the land birds is represented detected 31 times during the 2001/02 line transect census by endemics. They dominate most of the island’s habitat and based on this a total population of 155 individu- types, even such ones of allochthonous vegetation. Thus, als was calculated. Their numbers were mostly similar although the island shows much lower bird numbers than throughout the whole of Alejandro Selkirk. They were Robinson Crusoe, endemics still dominate the bird com- observed patrolling and perching in all habitat types munity against non-endemics. of the island. However, due to local winds and food sources some areas were more frequented than others. One concentration point was the small Las Casas settle- Population numbers of species ment, where in February 2002 more than ten individuals (mainly immature) were present. Higher concentrations The 2001/02 data give information of population sizes were also found near the mixed petrel colony of the of all resident land bird species and enable inter-specific southern upland. Taking these into account as well as the population comparisons. The broadest habitat spectrum (not registered) specimens of the habitat types 8, 9­b and 114

Tab. 1: List of ornithological line transect counts and their registration parameters on the Juan Fernández Islands during the spring/summer season of 2001/02. Species abbreviations: Am = Aphrastura masafuerae, Af = Anairetes fernandezianus, Afs = Asio flammeus suinda, Bpe = Buteo polyosoma exsul, Cob = Cinclodes oustaleti baeckstroemii, Cld = Columba livia f. domestica, Fsf = Falco sparverius fernandensis, Pd = Passer domesticus, Sf = Sephanoides fernandensis, Ss = Sephanoides sephaniodes, Tfm = Turdus falcklandii magellanicus. Other abbreviations: Alt. = Altitude above sea [m]; Date = Date and day time ; HT = Habitat type; Name = Local name of locations/route; No. = Running number; r = range; Spp./T. = Specimens number (per species); S.No. = Specimens number (total); ta = Transect area [ha]; tl = Transect length [m]; Tn = Species number (total); tw = Transect width [m]; Ws = Walking speed [km/h]; Wt = Walking time [min].

No. Name HT Alt. Date Ws Wt tl tw ta Tn S.No. Spp./T

1 S. J. Bautista–Mirador 5 80–185 10. xi. 2001, 17:55–18:05 3 10 (500) 50 2.5 3 7 1Sf 5Ss 1Tfm

2 S. J. Bautista–Mirador 2 226–325 10. xi. 2001, 18:21–18:37 3 16 (800) 20 1.6 3 8 1Sf 5Ss 2Tfm

3 S. J. Bautista–Mirador 3 330–440 10. xi. 2001, 18:45–18:56 3 11 (550) 20 1.1 1 1 1Ss

4 S. J. Bautista–Mirador 1c 440–565 10. xi. 2001, 19­:03–19­:18 2 15 (500) 50 2.5 4 15 4Af 4Sf 5Ss 2Tfm

5 S. J. Bautista–Plazoleta 5 50–100 12. xi. 2001, 7:07–7:12 3 5 (250) 50 1.25 3 10 5Sf 3Ss 2Tfm 3Af 1Sf 5Ss 6 S. J. Bautista–Plazoleta 2 100–230 12. xi. 2001, 7:14–7:37 3 23 (1150) 20 2.3 4 19 10Tfm 7 Plazoleta–Yunque 1b 265–29­5 12. xi. 2001, 7:49­–8:09­ 3 20 (1000) 50 5 4 26 6Af 6Sf 7Ss 7Tfm

8 S. J. Bautista–Plazoleta 2 120–260 12. xi. 2001, 8:14–8:31 3 17 (850) 20 1.7 4 10 2Af 2Sf 3Ss 3Tfm

9 S. J. Bautista–Plazoleta 5 80–105 12. xi. 2001, 8:39­–8:44 3 5 (250) 50 1.25 3 11 4Sf 6Ss 1Tfm

10 S. J. Bautista–Mirador 1c 435–550 14. xi. 2001, 6:59­–7:20 2 21 (700) 50 3.5 4 16 4Af 3Sf 6Ss 3Tfm

11 Mirador–S. J. Bautista 1c 453–550 14. xi. 2001, 7:23–7:43 2 20 (667) 50 3.335 4 18 6Sf 5Ss 5Af 2Tfm

12 Mirador–S. J. Bautista 3 350–453 14. xi. 2001, 7:56–8:06 3 10 (500) 20 1 2 5 2Ss 3Tfm

13 Mirador–S. J. Bautista 2 250–350 14. xi. 2001, 8:08–8:22 3 14 (700) 20 1.4 3 7 1Af 2Ss 4Tfm

14 Mirador–S. J. Bautista 5 95–210 14. xi. 2001, 8:29­–8:39­ 3 10 (500) 50 2.5 3 6 1Sf 4Ss 1Tfm 3Sf 13Ss 1Tfm 15 San Juan Bautista 4 10–50 15. xi. 2001, 7:04–7:18 (ca. 2) 14 500 50 2.5 4 32 15Pd 16 San Juan Bautista 4 10–50 15. xi. 2001, 7:49­–8:02 (ca. 2) 13 500 50 2.5 3 37 1Sf 18Ss 18Pd

17 S. J. Bautista–Plazoleta 5 80–105 15. xi. 2001, 8:08–8:13 3 5 (250) 50 1.25 3 9 1Sf 7Ss 1Tfm

18 S. J. Bautista–Plazoleta 2 120–260 15. xi. 2001, 8:18–8:33 3 15 (750) 20 1.5 4 17 2Af 1Sf 7Ss 7Tfm eschweizerbartxxx sng- 19 Plazoleta–El Yunque 1b 260–300 15. xi. 2001, 8:37–8:47 2 10 (333) 50 1.665 4 18 6Af 3Sf 5Ss 4Tfm

20 Plazoleta–Yunque 1b 265–29­5 15. xi. 2001, 9­:42–9­:51 3 9 (450) 50 2.25 4 14 2Af 3Sf 5Ss 4Tfm

21 Plazoleta–S. J. Bautista 2 100–230 15. xi. 2001, 10:00–10:15 3 15 (750) 20 1.5 3 12 1Af 7Ss 4Tfm

22 Plazoleta–El Yunque 1b 249–295 19­. xi. 2001, 16:15–16:27 3 12 (600) 20 1.2 3 8 2Af 2Ss 4Tfm 1Sf 24Ss 24Pd 23 San Juan Bautista 4 10–50 21. xi. 2001, 7:01–7:14 (ca. 2) 13 500 50 2.5 4 50 1Tfm 1Af 1Sf 10Ss 24 S. J. Bautista–Mirador 5 90–110 21. xi. 2001, 7:35–7:40 3 5 (250) 50 1.25 4 14 2Tfm 1Sf 12Ss 17Pd 25 San Juan Bautista 4 10–50 21. xi. 2001, 7:46–7:59­ (ca. 2) 13 500 50 2.5 4 31 1Tfm 26 P. Ingles–Cerro Alto 1a 290–400 26. xi. 2001, 18:16–18:29­ 2 13 (433) 50 2.165 3 19 9­Af 4Ss 6Tfm

27 P. Ingles–Cerro Alto 2* 150–200 26. xi. 2001, 18:40–18:50 2 10 (333) 50 1.665 2 8 3Cld 5Tfm

28 P. Ingles–La Pichuoa 6 0–10 27. xi. 2001, 18:03–18:35 3 32 (1600) 100 16 2 26 24Cld 2Fsf

29 P. Ingles–Cerro Alto 6 0–200 28. xi. 2001, 11:09­–11:33 3 24 (1200) 200 24 3 48 42Cld 2Ss 4Tfm

30 P. Ingles–Cerro Alto 1a 320–410 10. xii. 2001, 14:16–14:28 1.5 12 (300) 50 1.5 [1] 11 11Af

31 P. Frances – Pied. Agu. 6 5–200 04. i. 2002, 17:15–18:45 2.5 90 (3750) 200 75 3 11 1Afs 9­Cld 1Fsf

32 La Punta–El Puente 6 80–180 11. i. 2002, 12:33–13:04 3.5 31 (1808) 200 36.16 1 2 2Fsf

33 El Puente–La Punta 6 50–170 11. i. 2002, 13:42–14:15 3.5 33 (19­25) 200 38.5 0 0 0

34 La Punta–Villagra 6 100–210 11. i. 2002, 15:10–17:55 3 165 (8250) 200 165 2 63 62Cld 1Fsf

35 S. J. Bautista–Mirador 1c 440–565 11. i. 2002, 19­:08–19­:32 2 24 (800) 50 4 4 15 3Af 3Sf 8Ss 1Tfm

36 S. J. Bautista–Mirador 3 330–440 11. i. 2002, 19­:35–19­:43 3 8 (400) 20 0.8 1 1 1Tfm

37 S. J. Bautista–Mirador 2 250–330 11. i. 2002, 19­:43–19­:53 3 10 (500) 20 1 2 12 5Ss 7Tfm

38 S. J. Bautista–Mirador 5 180–250 11. i. 2002, 19­:58–20:04 3 6 (300) 50 1.5 1 3 3Ss

39­ Las Casas–P. Grande 12 10–170 24. i. 2002, 18:35–19­:22 3 47 (2350) 50 11.75 [1] 8 8Cob

40 Avenida de las Capras 9­b/11b 89­6–1178 25. i. 2002, 18:50–19­:25 3 35 (1750) 300 52.5 [1] 2 2Tfm

41 Avenida de las Capras 11b 1088–1227 26. i. 2002, 20:03–20:21 (ca. 3) 18 900 100 9 [2] 10 5Cob 5Tfm 115

No. Name HT Alt. Date Ws Wt tl tw ta Tn S.No. Spp./T

42 Avenida de las Capras 11b 1204–1257 26. i. 2002, 19­:44–19­:58 3 14 (700) 100 7 [2] 8 6Cob 2Tfm

43 Q. Casas–Lager 9­a/12 0–1000 30. i. 2002, 9­:45–12:45 2 180 (6000) 300 180 [1] 6 6Bpe 8Am 5Bpe 3Cob 44 Lager–Pico Inocentes 10/11a 1000–1340 31. i. 2002, 12:42–13:33 2 51 (1700) 400 68 4 19 3Tfm 8Am 6Bpe 4Cob 45 Lager–Pico Inocentes 10/11a 1000–1333 31. i. 2002, 20:47–21:38 2 51 (1700) 400 68 4 23 5Tfm 8Am 6Bpe 1Cob 46 Q. Vacas–Vista Loberia 9­a/10 9­9­0–1070 01. ii. 2002, 09­:23–10:35 2 72 (2400) 400 9­6 4 20 5Tfm 47 Q. Vacas–Vista Loberia 9­a/10 1008–1100 01. ii. 2002, 12:35–13:47 2 72 (2400) 400 9­6 3 19 7Am 7Bpe 5Tfm

48 P. Inocentes westward 10/11a 1200–1333 03. ii. 2002, 14:00–14:33 2 33 (1100) 400 44 [3] 12 5Am 1Bpe 6Cob

49 Beach–Posa Q. Vaca 10/12 0–230 06. ii. 2002, 11:30–13:30 1.5 120 (3000) 50 15 [1] 16 16Cob 1–6, 1.5– Σ/r 9–12 0–1333 10. xi. 2001–6. ii. 2002 3.5 1472 59­ 89­9­ 5270 1066.09­ 11 763 see Tab. 2

11b, the total island population of the Másafuera Hawk These sources, although basing on general observation, is estimated at 250. give no indication on fluctuations and/or trends during Previous statements on the abundance imply that this earlier period. The 19­9­4/9­5 data resulted from the Másafuera Hawks were less common through most of first technical census for this endemic kestrel and led to the last century (Lönnberg 1921, Johnson 1965, Brooke a population estimate of about 100 specimens on Robin- 19­87). Bäckström (according to Lönnberg 19­21) postu- son Crusoe and about 5 on Santa Clara. These popula- lated that they were even less abundant around the turn tion numbers seem to be in agreement with the previous of the penultimate century, as prisoners were hunting abundance descriptions. However, at least the (main) them during the island’s convict time. For the 19­9­4/9­5 population on Robinson Crusoe obviously has decreased season a population of 150 Másafuera Hawks on Ale- during the seven year period. This is confirmed by ad- jandro Selkirk was estimated. Thus the population has ditional general observations on occurrence and line clearly increased during these seven years. This tendency transect census. Walking the same two routes (28 & 33, is supported by general observations as well as by indi- Tab. 1), less specimens were registered in 2001 than in vidual numbers of censuses: walking exactly the same 19­9­4/9­5. two line transect routs (43 & 46, Tab. 1), 12 contacts Feral Pigeons Columba livia f. domestica (Gmelin were recorded in 2002 compared to only 7 ineschweizerbartxxx 1 sng-9­9­4/9­5. 1789) (Columbiformes, Columbidae) were recorded 140 The Juan Fernández American Kestrel Falco times during technical census on Robinson Crusoe in sparverius fernandensis (Chapman 1915) (Falconi- 2001/02. Based on this a total island population of 1121 formes, Falconidae) was recorded 6 times during the was calculated. Feral Pigeons also inhabit Santa Clara. line transect census and based on this a population of Previously there may have been a population on Ale- 46 was calculated for Robinson Crusoe. It breeds on jandro Selkirk too (Martin 1909), but in 19­17 Bäck- Robinson Crusoe and Santa Clara. On Alejandro Selkirk ström did not find them any more (Lönnberg 19­21). On only few individuals were seen in previous time (Torres Robinson Crusoe only altitudes lower than 400 m are 1970, Bourne 19­83a, Brooke 19­87) that probably did frequently visited. More horizontal and flat grasslands not breed. Most specimens were observed in lower al- near the sea are favoured for feeding, like in the valleys titudes of the habitat types 6 (and 7 in 19­9­4). However, Puerto Frances, Puerto Ingles, and Villagra (habitat type Juan Fernández Kestrels occasionally also may be pass- 6). Most pigeons were registered in the western part of ing by other habitat types of Robinson Crusoe like the Robinson Crusoe, mainly in large flocks, whereas they upland forests. Their preferred habitat stretches from the occurred in smaller groups in the South-east. Breeding rocks and cliffs near the shoreline to the lower timber- habitats are obviously the lava walls and cliffs along line, where scarce vegetation and grasslands are charac- the seashore, where they nest in natural holes “formed teristic. Torres & Aguayo (19­71) state that kestrels were by wind and weather” (Schalow 1899, Lönnberg 19­21, seen frequently near the breeding sites of pigeons along own observation). It is problematic to reliably estimate the cliffs. The calculation on base of the few line transect the population size, as feral pigeons show high mobil- records is suitable as a rough indication only. However, ity, occur in flocks and thus possess a highly unequal taking also further observations of occurrence and abun- distribution pattern. However, the census counts covered dance into account, the total population on Robinson a large area (354.66 ha) of the pigeons’ preferred habitat Crusoe is estimated at only 50 specimens. type (6). Data may be interpreted in the sense of indica- The statements of Schalow (1899), Lönnberg (1921), tion only. For 2001/02 Robinson Crusoe’s population is Johnson (1965), Bourne (19­83b) and Brooke (19­87) estimated at about 800. show that Juan Fernández Kestrels were “common” dur- Feral Pigeons have not been mentioned in sailor re- ing these times and often were seen at lower altitudes. ports from 1681 and 1707 (Funnel 1707). Then Audouin 116

Tab. 2: Recorded and calculated land bird numbers of the Juan Fernández Islands basing on line transect counts during the spring/ summer season of 2001/02. Habitat types are attached to a nativity code: u = predominantly autochthonous; l = predominantly al- lochthonous; h = about half autochthonous and half allochthonous. Transect count area is the sum of single counts per habitat type, with parentheses [value] indicating differing area for single species (comp. tab. 1). Their numbers mean: Robinson Crusoe (4711 ha): 1 = Forest of the montane region, 2 = Scrub vegetation of the lower region, 3 = Scrub vegetation of the mountain ridges, 4 = Cultivated land and gardens of the settlement area, 5 = Cultivated forest of the basal region near the settlement, 6 = Grasslands, rocky and erosive terrain of the basal region. Santa Clara (223 ha): 7 = Grasslands, rocky and erosive terrain of the basal region. Alejandro Selkirk (4446 ha): 8 = Forest of the montane region, 9­a = Tree-fern stands of the sub-alpine region, 9­b = Vegetation complex of the sub-alpine region, 10 = Vegetation of steep rock walls and canyon sides, 11a = Fern stands of the alpine summit region, 11b = Vegetation complex of the alpine region, 12 = Grasslands, rocky and erosive terrain of the basal region. Values and symbols mean: empty cell = no record during census counts and other observations; X = no census count carried out but species was present during other observations; x = no record during census counts but during other observations (thus species is rare); value in parentheses = bird records of transect counts; value without parentheses = calculated total bird number.

Robinson Crusoe S.C. Alejandro Selkirk Habitat type 1 2 3 4 5 6 7 8 9a 9b 10 11a 11b 12 Σ Nativity code u l h l l l l u u l h u l l Altitudinal range 150– 70– 0– 350– 550– 550– 200– 1100– 1100– 220–650 100–360 915 0–100 170 0–400 375 750 1100 1100 1300 1333 1250 0–550 4, 7, 10, 2, 6, 8, 15, 1, 5, Transect count numbers 9­, 14, 28, 29­, 43, 44, 45, 39­, 11, 19­, 20, 13, 18, 3, 12, 16, 17, 31, 32, 46, 40 46, 47, 44, 40, 41, 43, (compare Tab. 1) 22, 26, 30, 21, 27, 36 23, 24, 33, 34 47 48, 49­ 45, 48 42 49 35 37 25, 38 Habitat type area [ha] 990 290 599 39­ 70 2723 223 194 445 79­2 9­9­8 67 120 1830 9­380 164, Transect count area [ha] 27.115 12.665 2.9­ 10 11.5 354.66 0 0 9­6 26.25 186 90 16 19­.25 1066.0 [186] [19­3.5] [42.25] [9­0] 9 Short-eared Owl (1) (1) 8 X 8 Feral Pigeon (3) (137) (140) 69­ x 1052 X 1121 Juan Fernández Kestrel (6) (6) x x 46 X 46 House Sparrow (74) (74) 28eschweizerbartxxx9­ sng- 289­ Juan Fernández Tit-Tyrant (52) (9­) (1) (62) 189­9­ 206 x 6 2111 Juan Fernández Firecrown (28) (5) (6) (13) (52) 1042 114 23 79­ 1258 Green-backed Firecrown (47) (34) (3) (67) (38) (2) (19­1) 1748 779­ 620 261 231 15 3654 Austral Thrush (33) (42) (4) (3) (8) (4) (5) (1) (9­) (4) (8) (121) 1228 9­62 826 12 49 31 X 23 30 55 4 23 3243 Másafuera Hawk (9­.5) (12.5) (6) (3) (31) X 23 x 67 4 x 61 155 Másafuera Cinclodes (0.5) (15) (6.5) (11) (16) (49­) 2 x 77 5 83 1521 1688 Másafuera Rayadito (7.5) (18) (10.5) (36) 35 9­7 8 140 (160) (9­3) (7) (150) (60) (150) (22.5) (1) (54.5) (27) (19­) (19­) (763) Sum 59­17 2130 1446 585 365 1152 83 30 29­6 21 106 1582 13713

(1830) detected them first on Robinson Crusoe, but did specimens on Robinson Crusoe and about 200 on Santa not make a quantitative statement. In the late 19­th cen- Clara. The habitat type (7) on Santa Clara obviously was tury Plate (according to Schalow 189­9­) saw the pigeons the archipelago’s most suitable one for Feral Pigeons in great numbers (“in grosser Menge”, translation by and all island parts up to the 375 m high summit were the authors) and in 19­17 Bäckström (according to Lön- inhabited. The higher abundance of pigeons on this small nberg 19­21) states the Feral Pigeon to be an abundant island may be related to the absence of introduced preda- breeding bird. Contrarily, Brooke (19­87) estimates the tors like cats and rats, and the lack of human hunting population size of Robinson Crusoe and Santa Clara at activity. probably only a few hundred specimens. In 19­9­4/9­5 we Short-eared Owls Asio flammeus suinda (Vieillot estimated the population on base of line transect counts 1817) (Strigiformes, Strigidae) were recorded by only and additional behavioural observations at about 1000 one specimen during the census registrations. They 117

Fig. 2: Total population numbers of land birds of the Juan Fernández Islands: all eleven resident breeding species were covered by the 19­9­4/9­5 and 2001/02 censuses, respectively. The non-endemics Turdus falcklandii magellanicus and Sephanoides sephaniodes reach the highest population sizes, both on Robinson Crusoe.

eschweizerbartxxx sng- live on Robinson Crusoe and Santa Clara. Up to this The Green-backed Firecrown Sephanoides sephani- investigations only a single specimen was observed on odes (Lesson & Garnot 1827) (Caprimulgiformes, Tro- Alejandro Selkirk (in 19­9­0, pers. comm. V. Camacho), chilidae) was recorded 19­1 times during the line transect perching on a tree-fern Dicksonia externa in the south- census, more often than any other bird species. Basing ern upland. Short-eared Owls were active from about on this number a total population of 3654 specimens 3 p.m. onwards, mainly in open habitat types (6 and 7). is calculated for 2001/02 on Robinson Crusoe. It was However, they have been observed also in trees of the documented from all six habitat types of the island, but lower timberline, where they were able to control the was most abundant in some allochthonous ones (2, 4 & grasslands. The behaviour and environmental demands 5). Although being less abundant in the autochthonous of this non-endemic form respond to observations of forest (habitat type 1), nevertheless such native vegeta- continental specimens in other parts of southern South tion hosts significant parts of its population. In lack of America (comp. Rau et al. 19­9­1, Humphrey et al. 19­70). suitable habitats, the Green-backed Firecrown is absent Previous observers did see Short-eared Owls only on from Santa Clara, but was observed on Alejandro Selkirk Santa Clara (Brooke 19­87) or in the dry western part of since 19­81 (Bourne 19­83a). It survived there in small Robinson Crusoe (Plate according to Schalow 1899, numbers (Brooke 19­87) until at least 19­9­3 (own ob- Bäckström according to Lönnberg 19­21). By observa- servation). However, it had disappeared in 19­9­5 (Hahn tions additional to the census counts, they were detected 19­9­8) and was not seen in 2002, too. The census tech- at a number of new sites in 2001/02: Puerto Francés, Pie- nique worked well for the two hummingbird species. dra Agujereada, Pangal, Puerto Ingles, and La Vaquería However, in regard to the breeding activities during the all hosted one breeding pair. It is obvious that the popu- study period and the high mobility of this species, not all lation size may only be roughly estimated, both related specimens of a certain transect may have been recorded. to behaviour/method and the few observations made. Thus the total population size of Robinson Crusoe is es- However, the total population size of Robinson Crusoe timated higher at 4500. and Santa Clara does not seem to exceed 50 specimens. The Green-backed Firecrown is not native on the ar- There is not sufficient data to give any indication on chipelago (cf. Colwell 19­89­, Roy et al. 19­9­8), but prob- population tendencies. ably reached it earlier than 1830, as Audouin (1830) 118

Fig. 3: Total population numbers of land birds of Robinson Crusoe Island: all eight breeding species were covered by the 19­9­4 and 2001/02 censuses, respectively.

reported on “trois colibris” from Robinson Crusoe. He to the Green-backed Firecrown it inhabits several habitat probably meant the two different sexes of the Juaneschweizerbartxxx sng- Fern- types (1, 2, 4 & 5), but seems to avoid allochthonous ández Firecrown and (the only poorly different sexes of) ones of monotonous or open structure (3 & 6). Further the Green-backed Firecrown. Its population develop- quantitative differences between the two hummingbird ment may be reconstructed partly, interpreting the few species are: Juan Fernández Firecrowns were recorded early and some more recent reports (Audouin 1830, data in more than three quarters of the montane forest counts from 1870 according to Reed 1874, data from 19­73 ac- (habitat type 1), always with several specimens. In al- cording to Colwell 19­89­, Brooke 1987, Stiles 19­87): lochthonous scrub vegetation (habitat type 2) they were according to these sources the species probably reached detected only in half of the transect counts, mostly with the archipelago between 1574 and 1830, but was by only one specimen. Thus, contrarily to the Green-backed no means common until 1870. In the following years Firecrown which reaches higher densities in alloch- the population increased, surpassed the one of the Juan thonous habitat types, the Juan Fernández Firecrown is Fernández Firecrown and meanwhile has reached clearly by far more abundant in the autochthonous forest habi- higher specimen numbers. Comparison of population tats. Facing the significant area of these forests, more estimates from 19­73 to 19­89­ (Brooke 1987, Stiles 1987, than 80% of the total population of this endemic species Colwell 1989, Mesa 1988, 1989) do not indicate any is located here. On base of the census data it occurs from population trends within this period. However, using the sea-level at least up to 565 m. Hahn (19­9­8) observed same method and criteria, we estimated a population size it up to 59­0 m altitude. Schiller (pers. comm. 19­9­4) of 6000 in 19­9­4. This would mean that the population and Danton (pers. comm. 2001) reported it from the had decreased to 75% of its size seven years ago. Con- mountains La Piña and El Yunque (9­15 m), respectively. tact numbers of 16 transect counts of exactly the same As blooming Eucalyptus trees were especially frequent routes show that only 107 specimens were registered in along transect routs (of the habitat types 2, 4 & 5), con- 2001/02 compared to 146 specimens in 19­9­4. tacts were over proportional. Therefore the population is The Juan Fernández Firecrown Sephanoides fern- estimated lower, at 1100 specimens for 2001/02. andensis (King 1830) (Caprimulgiformes, Trochilidae) The population development of the Juan Fernández was recorded 52 times during the line transect counts on Firecrown may be partially reconstructed. The endemic Robinson Crusoe. Based on this a total population size subspecies Sephanoides fernandensis leyboldi was de- of 1258 specimens was calculated for 2001/02. Similar scribed by Gould (1870) on base of few specimens col- 119

Fig. 4: Total population numbers of land birds of Alejandro Selkirk Island: all four regular breeding species were covered by the 19­9­4/9­5 and 2002 censuses, respectively. Sephanoides sephaniodes occurs only occasionally and was not detected on the island in 2002.

lected by helpers of Leybold. However, the taxonomic ble. Although also observer criteria and different census differentiation is marginal, and type material disappearedeschweizerbartxxx sng- techniques have to be taken into account, both these from the museum collections. If ever existed (comp. estimates for 19­88 are below ours from 19­9­4, estimat- Johow 2003), it became extinct on Alejandro Selkirk ing a total population of 1300 specimens. This would shortly after its discovery. Only the botanist Skottsberg mean that the Juan Fernández Firecrown population had saw individuals in the wild in 19­08, but in 19­17 the gone through a population depression. However, facing zoologist Bäckström (Lönnberg 19­21) was not able to the recent estimate of 1100 specimens, the population record hummingbirds from Alejandro Selkirk, although may slightly decline again. Comparing data sets of 14 he spent several weeks on the island. The Juan Fern- counts of identical transect routes, the numbers of con- ández Firecrown also may have lived on Santa Clara, tacts dropped from 54 down to 24 in 2001/02. before the vegetation was destroyed by introduced goats. The Másafuera Grey-flanked Cinclodes Cinclodes Nowadays it is restricted to Robinson Crusoe. During oustaleti baeckstroemii Lönnberg 1921 (Passeriformes, the late 19­th century it must have been common on this Furnariidae) was registered during eight transect counts island (cf. Reed 1874, Marsley according to Colwell with 49­ specimens. A population size of 1688 was calcu- 19­89­). Around the turn of the penultimate century the lated. The Másafuera Cinclodes is endemic to Alejandro Juan Fernández Firecrown was still abundant, as Murray Selkirk, although single individuals have been seen on (according to Schalow 189­9­) calls it the most abundant Robinson Crusoe too (Lönnberg 19­21). On Alejandro (“gemeinste”; translation by the authors) bird species of Selkirk it was observed in all altitude levels up to the the island. In 19­17 it was still common in the forests of Los Inocentes summit at 1333 m and may be found in the island (Lönnberg 19­21). The chronologically next all habitat types. However, preferred landscape struc- estimates are from 19­73 (Colwell 19­89­) and 19­85/86 tures are the washes and v-shaped Quebradas, which (Brooke 19­87): here an extremely low population is also carry water in the summer. This is predominantly stated. Their estimates of 200-400 (Colwell 19­89­) and the case with the Quebradas Tongo, Varadero, Inocentes, 250 specimens (Brooke 19­87) represent the lowest ever. Vacas, Casas, Sanchez, and Guaton. The rocky beaches Already in 19­88 Mesa (19­89­) and Stone et al. (19­89­) are only inhabited where freshwater is nearby, for exam- estimated the total population at about 680 and 500- ple at the end of Quebrada Inocentes. However, Másafu- 1000 specimens. Both these estimates surpass the one era Cinclodes also may be abundant in upland regions of Brooke from the summer 19­85/86 for more than dou- where no permanent waters exist, like the habitat type 120

11b. These regions are moist and often covered with (1983a), Brooke (19­88), and Hahn (19­9­8). Some of clouds. Only exceptionally specimens may be seen either the few early visitors even failed to find it (e.g. Millie in dense vegetation (habitat types 8 & 9­b) or in the dry according to Johnson 1967, Torres & Aguayo 19­71). northern grasslands where no washes are near. Transect Therefore Vaurie (19­80) thought that it was probably counts through grasslands have taken place mostly along extinct. But then Bourne (19­83a) saw four individu- such washes (Q. Casas, Q. Vacas). Thus the calculated als. Thus, until this date the Másafuera Rayadito was number for this habitat type (12) is too high, and the total always called extremely rare or could not be found at population is estimated lower at about 1500 specimens. all. In 19­86 Brooke (19­87, 19­88) was the first one trying To reconstruct the population development of the to estimate the population. Most of all his results were Másafuera Cinclodes only very few indicators are found. valuable, as he was able to map the summer distribution For the year 19­17 Bäckström (Lönnberg 19­21) states range. He estimated the population roughly at “probably that the species was common in certain regions of Ale- about 500” birds, but less than 1000. Precise estimates jandro Selkirk. In 19­86 Brooke (19­87) calls it to be com- were difficult during these times (Brooke 19­88), as no mon too. In 19­9­4/9­5 we carried out first transect counts data was available on home range size, and it was not of the Másafuera Cinclodes that resulted in an estimate possible to distinguish individuals, like today (comp. of 1500 individuals. On this data base no population Hahn & Römer 19­9­6). Meanwhile vocalisation types trends or fluctuations can be reconstructed for historical and call numbers are known (Hahn & Mattes 2000). times. Apparently the Másafuera Cinclodes was widely This helps not only to identify home ranges, but also to distributed and quite common on Alejandro Selkirk dur- apply standardised census methodology. Brooke (19­88) ing the last century. Over the seven year period no obvi- had to summarise and average specimen numbers of the ous population changes are recognised too: comparing same area, which were detected during different counts. three transect counts of identical routes (39­, 41 & 42, It is unknown if his higher estimate results from different tab. 1), no significant difference in contact numbers is census/evaluation technique or from a real population found (20:19­). decrease until 19­9­2. In the summer seasons 19­9­2/9­3 and Másafuera Rayaditos Aphrastura masafuerae (Philippi 19­9­4/9­5 a census was carried out and the population & Landbeck 1866) (Passeriformes, Furnariidae) were estimated at 150 specimens. Thus, this extremely low detected 36 times during five long transect counts. Based population further declined from 19­9­2 to 2002. on this the total population was calculated at 140 speci- The Juan Fernández Tit-Tyrant Anairetes fernan- mens. The Másafuera Rayadito is endemic to Alejandro dezianus (Philippi 1857) (Passeriformes, Tyrannidae) is Selkirk. It occurs predominantly in intact sub-alpine endemic to Robinson Crusoe and was detected during and alpine vegetation above 800 m altitude. Observaeschweizerbartxxx sng- - 17 line transect counts with 62 specimens. Based on this tions below 800 m were generally rare. However, above a population size of 2111 is calculated. An early report 800 m only areas are inhabited in which the vegetation on its habitat is given by Schalow (189­9­), who states: is not degraded or destroyed by the introduced goats. ”Der Vogel ... lebt nach Art unserer Meisen im Blattwerk Indeed, only three different habitat types are inhabited der Bäume und Sträucher.” (The bird ... lives like our (9­a, 10 & 11a, tab. 2). Sub-alpine Dicksonia tree-fern tits in the foliage of trees and scrubs; translation by the stands (habitat type 9­a) are dominant up to about 1100 authors). Bäckström (Lönnberg 19­21) found it in the m altitude where the alpine Lophosoria fern stands be- forests and especially near the lower timberline. Bourne come more abundant and then dominate up to the Los (19­83b) saw it in the shrubs of the settlement and abun- Inocentes summit. The vegetation of steep rock walls dantly in the woods of the island. Brooke (19­87) re- and canyon sides (habitat type 10) is independent from ported this bird from all habitats dominated by woods in- the altitude level, but occurs wherever high incline is cluding exotic vegetation of the settlement. We confirm found. In allochthonous vegetation of high altitudes (9­b this last description, but saw it rarely in the monotonous & 11b), Másafuera Rayaditos were only seen by way of Eucalyptus-Pinus stands near the village. We also agree exception: generally they do not occupy home ranges if with Bäckström that density was high near the lower the cover of ferns and trees is less than about 50 percent, timberline, but also found it more abundant in valleys like in degraded areas of the northern upland. Aut-eco- and Quebradas than on mountain ridges. Although single logical investigations (Hahn et al. 2004) of their habitat individuals were detected in allochthonous habitat types demands, distribution patterns, home range size, and (3, 4 & 5), the majority of individuals was registered in species range confirm a realistic dimension of the calcu- the native forests (1). Tyrants have been detected dur- lation. Indeed, on base of these additional observations ing all ten forest counts, although transects often were the total population of the Másafuera Rayadito is esti- of small size; not less than 52 of the total 62 specimens mated at 140 specimens in 2002. were registered here. Contrary to Juan Fernández Fire- Only few indication sources help to reconstruct the crowns, they make little use of the allochthonous habitat species’ population development. It was documented types (2, 3, 4, 5 & 6): only during 6 of 28 transect counts by only four observers since description by Philippi & tyrants were registered here, always few. More than four Landbeck (1866): Bäckström (Lönnberg 1921), Bourne fifth of the population was located in the montane for- 121 ests, both in 19­9­4 and 2001/02. The calculation reflects On Robinson Crusoe thrushes were reported as abun- a realistic dimension, but as transect routes rarely led dant around the end of the 19­th century (Reed 1874, through optimal habitats the estimate is set little higher Schalow 189­9­), when allochthonous vegetation already at 2500 tit-tyrants in 2001/02. was widespread. A lower Selkirk population was always Only a few indications are useful to reconstruct popu- stated during the 20th century (Lönnberg 1921, Brooke lation development since island discovery. Probably the 1987). For Robinson Crusoe our first systematic thrush tit-tyrants once possessed a much larger distribution area census led to an estimate of about 6000 individuals in on Robinson Crusoe than at present, as forest habitats 19­9­4. This means a population decline to about the half shrunk. Now the species is abundant on one fifth of the of the size in 2001/02, within seven years. This reduction island only. Allochthonous habitat types of rich veg- was obviously the result of intensive thrush hunting by etation structure (2, 3, 4 & 5) cover another fifth of the CONAF park rangers. The idea behind it is to reduce the island but host only limited tit-tyrant numbers (comp. seed dispersal of introduced plants by (presumably non- tab. 1, nos. 6, 8, 13, 18, 21 & 24). The species was al- native) Austral Thrushes. ready common in forests in the late 19­th century (Reed House Sparrows Passer domesticus (Linnaeus 1758) 1874, Schalow 189­9­). Further observations during the (Passeriformes, Passeridae) were detected during all four 20th century (Lönnberg 19­21, Bourne 1983b, Brooke line transect counts that led through the settlement area 19­87) suggest similar abundances. In 19­9­4 we carried (habitat type 4), and individuals were contacted 74 times. out first transect counts and estimated the population at This is the only area on the archipelago where these non- about 3000 tit-tyrants. This means that the population native elements occur, reaching up to 100 m above sea- size slightly decreased until 2001/02. Although maybe level. The settlement San Juan Bautista is dominated by only perennial fluctuations are causative for the recent exotic plants and, of course, generally by human activity. decline, it should be further monitored. The population House Sparrows breed in a loose colony in branches of size has not reached critical limits yet. the two Araucaria trees near the central place (la plaza). Austral Thrushes Turdus falcklandii magellanicus As all relevant transect routes led along this colonisation (King 1851) (Passeriformes, Muscicapidae) were de- centre, the calculation is too high (tab. 2). Taking the tected during 37 of the 49­ line transect counts, with 121 transect counts, their routes and additional observation individual contacts. Thrushes are widely distributed on data into account, the total population is estimated at both major islands but are absent from Santa Clara. They about 80 sparrows for 2001/02. were observed in all habitat types of dense vegetation House Sparrows reached southern South America in and in all altitudes. On Robinson Crusoe most specimens 1850 (Johnson 19­67) and Chile in 19­04. On Juan Fernán- were observed in the allochthonous shrubeschweizerbartxxx vegetation sng- dez they landed in 19­43 on board of a ship coming from (habitat type 2), but during the breeding season they also Valparaiso (Summers-Smith 19­63). Since arrival they in- strongly frequented the autochthonous montane forests. habit the settlement San Juan Bautista on Robinson Cru- On Alejandro Selkirk they were generally less abundant, soe in small numbers. There are no indications that the but preferred allochthonous vegetation of the sub-alpine population has been significantly higher than in 2001/02. region (9­b) and of steep rock walls and canyon sides The estimates of Bourne (19­83b), Brooke (19­87) and (10). At the summit thrushes were seen by occasion only, ourselves from 19­9­4 suggest similar abundances. Maybe but were more abundant on the northern plateau (up to not only environment and food resources are limiting the 1250 m). For Robinson Crusoe a population of 3108 population size, but also high predation pressure. Juan thrushes is calculated. This fits with general observations Fernández Kestrels, domestic cats and rats occur in the of distribution and abundance: the population is esti- settlement area. Even rats have been observed to prey mated at about 3000 specimens. The Selkirk population on (adult) House Sparrows (Römer 19­9­5). After 19­43 is clearly lower, maybe in relation to vegetation charac- Alejandro Selkirk had been reached by sparrows as well ters and Másafuera Hawk presence. However, transect (Bourne 19­83a) and broods were observed in 19­9­2/9­3 counts and calculations not seem to be representative, (own observation). However, in 19­9­4 the last House Spar- related to thrush hiding in the vegetation and local daily row disappeared from Alejandro Selkirk, maybe as the migrations. The population size is roughly estimated at island remains uninhabited during winter and Másafuera about 1000 individuals for Alejandro Selkirk. Hawks are abundant around the fishermen huts.

Discussion

The significant differences in species composition before the investigation, partly because both islands have and population numbers between the two major islands a number of basic features in common: geographic lati- of the Juan Fernandez archipelago were not expected tude, size dimension, geologic origin, geomorphologic 122

structure, biogeographic relation, even aspects of plant tive tendency of this small falcon might be competition life and anthropogenic history. However, analysing the and predation by Short-eared Owl, human pressure, and environmental conditions for birds more in detail, sev- potential nest predation by mature rats and cats. eral causes may be identified. The high densities of non- The Juan Fernandez Firecrown faced a variety of endemics on Robinson Crusoe are probably supported by threats during the past centuries: intensive collecting the wide distribution of allochthonous habitat types. The by humans, comprehensive habitat loss, competition by non-endemics already have co-existed for long time with immigrated Green-backed Firecrown, and predation by many of the allochthonous plant species on the main- introduced mammals. Maybe this species previously oc- land, where they may have adapted to them. For example curred on Santa Clara and Alejandro Selkirk too (comp. the Green-backed Firecrown is able to aliment from the Gould 1870, Johow 2003), and thus is highly prone to flowers of Aristotelia chilensis much more efficient than extinction. For a detailed conservation discussion of the the Juan Fernández Firecrown (cf. Barros 1952, Stone islands’ most recognised flagship species refer to Col- et al. 19­89­), and in turn encourages this allochthonous well (1989), Bourne et al. (19­9­2), and Roy et al. (19­9­9­). plant by pollination. The Austral Thrush feeds on the To our observations, the most critical factors (beneath numerous berries of Aristotelia chilensis, Ugni molinae general habitat loss) are disappearance of native hum- and Rubus ulmifolius, and endozoochorously disperses mingbird plants from the wild, plantation of small/low their seeds all over the island. Even on top of the moun- flowering plants in the settlement (even if native), and tain El Yunque young brambles have been found (R. especially the high domestic cat population in the set- Schiller pers. comm. 19­9­5). These highly successful tlement. invasive plants have not yet managed to establish signifi- The Másafuera Rayadito has faced similar threats, cant stands on Alejandro Selkirk, explaining at least the but not has to compete with newly arrived bird species lower populations of Austral Thrush and Green-backed and was never intensively collected (only 13 specimens Firecrown. in museum collections around the world: Vaurie 19­80). Besides habitat factors, the generally high population However, it has to be classified as the most threatened numbers of some non-endemic land birds and low num- bird species of the archipelago, now showing a popula- bers of most endemics may be linked to competition and tion size being as low as 140 individuals. Habitat de- predation. Continental forms are more often aggressive struction, mainly through man-made fires and introduced than island forms. Indeed, competition and aggressive goats, is valued as the most serious concern for its criti- behaviour was observed between Green-backed and Juan cal situation. During field work we detected feral cats Fernández Firecrown (Stiles 1987, Mesa 1988, 1989, Felis silvestris (Schreber 1775), f. catus, (Mammalia,

Colwell 1989, Stone et al. 1989, Brooke 1987,eschweizerbartxxx sng- Roy Felidae), Ship rats Rattus rattus (Linnaeus 1758), Nor- et al. 19­9­9­). Carlquist (19­74) states that island forms way rats Rattus norvegicus (Berkenhout 1769­), and often show reduced reproduction rates; number and size House mice Mus musculus Linnaeus 1758 (all Mam- of clutches of island forms are often smaller than that malia, Muridae) within its 1000 ha species range. These of their allies on the mainland. This island strategy may are likely to have a negative effect on adult rayaditos and have been reasonable and successful in the past, but in- broods too. Conservation management for the Masafuera vasions of alien predators probably have turned it into a Rayadito must include the total eradication of introduced disadvantage for endemics. Especially cat and rat preda- goats, cattle, cats, mice, and rats. More detailed studies tion is critical to terrestrial island birds (Atkinson 1985, of the breeding ecology are urgently needed, especially Moors 19­85), and was detected for several species of the reproduction success is evident. Juan Fernandez Islands (Brooke 1987, Cuevas & van Prime conservation aim for the whole archipelago Leersum 2001, Hahn & Römer 2002). has to be the eradication of all introduced mammal spe- Juan Fernández Firecrown, Juan Fernández Tit-Ty- cies, both habitat destroyers and predators. Eradication rant, and Másafuera Rayadito possess a range which campaigns should start as soon as possible with goats each is smaller than 15% of the archipelago area. Ac- on Alejandro Selkirk, rabbits on Santa Clara, and cats in cording to small population numbers, the status of Juan the settlement of Robinson Crusoe. On Santa Clara all Fernandez Firecrown, Juan Fernandez Kestrel, and es- introduced species may be wiped out quickly because of pecially Másafuera Rayadito is critical. The kestrel is an the island’s smaller size. Then it may be used as a natural endemic on subspecies level. Its territory sizes and spa- refuge for some endangered species. tial demands may limit population to a theoretical maxi- mum of a few hundred birds, as suggested on base of comparative data from kestrels on the mainland (comp. Figueroa & Corales 2002). However, its present popu- Acknowledgements lation size (~ 55 ind.) is clearly below such a potential, especially facing the increased open terrain and the addi- We are grateful to Chilean CONAF for island work permis- tional food sources on Robinson Crusoe and Santa Clara. sions (V. Region: 03/9­4 & 011/01), especially to M. Galvez, J. Possible reasons for the small population and the nega- Reyes, J. Mesa, G. Gonzalez, C. Diaz, and the rangers Alfonso, 123

Bernado, Danilo, Esteban, Guillermo, Manuel, Nino, Oscar, and and equipment. W. Beisenherz gave helpful comments on ear- Ramon Schiller. Thanks to the Rojas and López families on Juan lier manuscript drafts; J. Fjeldså and J. Haffer commented Ma- Fernández, and to J. Francis and H. Ochoa of NG expedition. M. safuera Rayadito ecology. The study was supported by DAAD Fernández, H. Mattes, G. Schulte and A. Vogel offered advice (19­9­4), FES (19­9­7–9­8) and AvH grants (2001–03).

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