UNIVERSITY OF COPENH AGEN FACULTY OR DEPARTMENT

Space use strategies of two Palaearctic migrants on the wintering grounds A study of winter territoriality in the Common Chiffchaff and Subalpine Warbler

Dina Abdelhafez Ali Mostafa

Supervisor: Kasper Thorup

Co-Supervisor: Torben Dabelsteen

Submitted on: 2 October, 2017

Name of department: Natural History Museum of Denmark Behavioural Ecology - Section of Ecology and Evolution - Department of Biology. University of Copenhagen

Author(s): Dina Abdelhafez Ali Mostafa

Title and subtitle: Space use strategies of two Palaearctic migrants on the wintering grounds : A study of winter territoriality in the Common Chiffchaff and Subalpine Warbler

Topic description: An investigation of the chosen space use strategies and territoriality in two migrant songbirds wintering in the Sahel.

Supervisor: Kasper Thorup – Torben Dablesteen

Submitted on: 2 October 2017

Grade:

Number of study units:

 2  3

2 Table of contents

PREFACE ...... 4

SUMMARY ...... 7

BACKGROUND ...... 9

Why study birds on their winter ground ...... 10

Sociality as an extension of space use strategies ...... 11

The winter strategies of the two species: what is known so far?...... 15 The species: ...... 15 Common Chiffchaff (Phylloscopus collybita) : ...... 15 Subalpine warbler (Sylvia cantillans): ...... 18

SPACE USE STRATEGIES IN TWO PALAEARCTIC SONGBIRD MIGRANTS IN WINTER: PATTERNS OF TERRITORIALITY, ASSOCIATION AND VOCALISATION IN THE COMMON CHIFFCHAFF AND SUBALPINE WARBLERS WINTERING IN NORTHERN SENEGAL...... 21

Abstract ...... 21

Introduction ...... 21

Materials and methods ...... 22 Study site...... 22 Radio tracking ...... 22 Playback experiments ...... 23 Statistical analyses ...... 24 Response to Playback ...... 25

Results ...... 26

Discussion ...... 31

Conclusion ...... 35

REFERENCES ...... 36

APPENDIX ...... 43

3 Preface

The idea behind this project started with my interest in the field of animal behaviour in general and communication in particular. To start with I was looking for a research topic that related to bioacoustics, which will present the opportunity to learn how to collect acoustic data and analyse it. The other behaviour that I wanted to learn about was animal migration, and ideally communication underway. Because I was very keen on carrying out fieldwork, I approached Professor Kasper Thorup at the National History Museum as his team currently studies migration in songbirds, and we started developing the idea for a thesis research. I also asked Professor Torben Dabelsteen to co- supervise, because of his expertise in animal behaviour in general and bioacoustic in particular, and he kindly agreed to. Bird song and calls during the breeding season are well studied for a myriad of species, but little is known about the occurrence and function of the former once breeding is accomplished. The original design of this study was to collect recordings of spontaneous winter song in a chosen songbird species and attempt to correlate it to a function, and to supplement that with playback experiments to investigate the birds’ reaction to conspecifics’ song. As breeding season singing is established to serve the function of attracting a mate and establishing/maintaining a territory, the hypothesis was that winter song should serve the latter purpose due to the absence of breeding during winter for migrants, and that this territory would be only used for foraging, as opposed to the breeding season territory that is also used for nesting and raising the young. In 2011, Kasper has collected some tracking data on four songbird species at the Djoudj National Park in Northern Senegal, where many migrant species that breed in Eurasia spend the northern winter season. We found conflicting reports of winter song in the Common Chiffchaff in the literature, and similarly for the closely related species Willow Warbler, and decided to focus on the former since a recent study investigated the behaviour in Willow Warblers in 2014. I performed some preliminary analyses using the tracking data for 2 of those species to detect the existing patterns of space use – territoriality or otherwise – and to find out if any flocking patterns existed for the Chiffchaffs. The results did not support either territoriality or flocking for the Chiffchaffs, but showed evidence for territoriality in Subalpine Warblers. Therefore the second species we chose as was Subalpine Warbler, as a species exhibiting territoriality in winter, its behaviour offers a clear point of comparison for the species of main interest. Due to scheduling difficulties, the field work ended up taking place during the end of the northern winter season, right during the departure of Chiffchaffs from the study site in Northern

4 Senegal. During the period of fieldwork, the numbers of Subalpine Warblers were sufficient for the purposes of the study. On site, pilot trials showed that Chiffchaffs did not sing spontaneously, nor did they respond vocally to playback of conspecifics’ song. Accordingly, the focus was shifted to documenting the behavioural responses during the playback session. The playback data was then used along with the tracking data from 2011 to construct a multi faceted picture of the two species’ use of their environment, showing home range sizes, flocking/association patterns for Chiffchaffs only – since a territorial species like Subalpine Warblers will not associate- and responses to conspecifics’ song. This report consists of two parts; the first part is an introduction where I try to present the basic concepts and current knowledge in areas relevant to the study. Concepts like migration and types of space use strategies are presented, followed by a look at the ecology of the two migrants of interest on their wintering range. I will therefore present a summary of what is currently known of the two species’ ecology on their breeding and non breeding ranges for contrast The second part of the report is the manuscript that present the investigation carried out in Senegal. First, I present the investigation of association patterns and home range sizes and their overlap for individuals of the two species using tracking data collected during January 2012 at Djoudj National Park in the north of Senegal. The second part investigates the territorial behaviour of the two species using playback experiments to quantify the presence and degree of aggression triggered by conspecifics song; these experiments were carried out at the same site during February/March 2017. The results are then compared to previous studies of the same methods that were conducted on Willow Warbler, a species that is native to Denmark and is closely related to the common Chiffchaff. Special attention is paid to the fact that the tracking data and playback experiments were conducted during different portions of the winter season, and also to the difference in locality for the comparison between the Chiffchaff and the Willow Warbler.

I would like to thank everyone who helped and contributed to the process of my learning the valuable knowledge I amassed working on this project. First, thanks to my two supervisors for the knowledge and insights they shared and for being available all the time to answer questions, correct my direction and discuss my ideas. I would also like to give special thanks to Mikkel Willemoes for the endless help with all the aspects of my project work, from teaching me all I 5 know about fieldwork to helping me with the statistical analyses and answering questions, even in the middle of the busiest time of fieldwork season. Special thanks to Thomas Mondain- Monval from the Lancaster Environment Centre at Lancaster University for his help and support on the data collection site. Thanks to Mathilde Lerche-Jørgensen for her help with R, To Lykke Pedersen for the valuable fieldwork experience, to Katherine Snell for the help with research ideas, to Manuel Nagel from the social evolution group for his help with the literature written in German, and to Tabitha Innocent and Sylvia Mathiasen from the social evolution group for all the moral support.

6 Summary

Breeding season territoriality is typical of songbirds and the territory serves for nesting, foraging and raising the young. Out of the breeding season, territorial behaviour persists in some species to different degrees during autumn and has been documented in many during winter, including migrant species. Typical territorial defence is carried out through vocalisation, which could be spontaneous to advertise the territory, or following territory invasion. This study investigates the space use strategies in two Palaearctic songbird species, the Common Chiffchaff and the Subalpine Warbler, using tracking data and playback experiments on a winter site where the two species occur in Northern Senegal. To our knowledge, no similar studies have been done on either of the two species, although some descriptive studies reported singing outside of the breeding season for both. The tracking was carried out during the northern winter of 2011, where 11 Chiffchaffs and 5 Subalpine Warblers were tracked at least twice a day for a period between 4 and 12 days, resulting in minimum of 17 and maximum of 39 relocations for each individual. The tracking data was used to construct the home range for each individual using 95 % and 50 % Minimum Convex Polygon, as well as 90 and 50 fixed Kernel Density with href smoothing factor. We also calculated two space use indexes, PHRi,j which approximates the probability of individual “i” being in the home range of individual “j”, and UDOI which represents the utilisation of overlap areas. The means of the above were compared for the two species using a two sample t-test assuming non equal variance. These analyses showed a trend towards larger home ranges and overlaps for Chiffchaffs compared to Subalpine Warblers, albeit no significant different in means was found except for the UDOI index, the difference in the latter being highly significant with P =0.0005. We also used the tracking data to investigate association patterns in Chiffchaffs by using the relocations for each pair of individuals tracked within an hour of each other to calculate the distance separating them. These distances were then compared to a random population of distances created using the same relocations to perform a bootstrap test followed by a Bonferroni correction. None of the pairwise distances were found to be different from the mean of the random distribution, nor was there a correlation between the distance between the pair and the time between tracking each of them. The Playback experiments were carried out using recordings of conspecific song for each species, which was played for minimum of 5 minutes, during which the response, both behavioural and vocal, of a focal individual was noted and recorded. Total number of 7 experiments was 69 for Chiffchaff and 106 for Subalpine Warblers. The responses were divided into a categorical group, which included the presence/absence of a given response, and a continuous measures group, which included the magnitude of responses in a given category. The percentages that approached the speaker were 23% for Chiffchaff and 80% for Subalpine Warbler. Of those that approached the speaker, Subalpine Warblers spent significantly longer time close to the speaker in particular and on site in general compared to Chiffchaffs, but no significant difference was seen between the two species in the approach distance and latency. For the rest of the categories, only Subalpine warbler showed a response, with 64% calling and 14% singing in response to playback, while in 39% of the trials where conspecifics were present – n = 28 – one of the present individuals chased the other off site. The obtained results do not show any evidence of territoriality nor flocking in Chiffchaffs, but strongly confirm the territorial behaviour in Subalpine Warblers. We believe the absence of significant difference between most of the calculated indices ranges and overlaps to be caused by the small sample size of tracked Subalpine Warblers and the presence of one outlier individual whose home range is very large.

8 Background

Seasonal changes in habitat quality are believed to have exerted selections pressure on many bird species to evolve into long distant migrants that can exploit the resource abundance at habitats thousands of kilometres apart. These species are found all over the globe and they typically undertake migration in the autumn and in the spring, traversing formidable obstacles and distances. A large number of species across all bird families breed in the temperate regions during summer, capitalising on the abundant food supplies to maximise the chances of their reproductive success. Once breeding season is over, these birds go through a number of changes in preparation for leaving the breeding range, before chances of survival decrease, and then they head to their tropical wintering ranges. Success in reproduction and survival is what constitutes fitness, and thus it is the motivation that explains most of the decisions an animal makes. Every strategy an animal employs towards achieving increased fitness comes at a caloric cost and time investment, and that cost has to be outweighed by the benefits an animal incurs for the strategy to be adaptive. Because reproduction is seasonal in birds, some strategies are beneficial during breeding season despite their high cost. Space use strategies for example can range from solitary to flocking and from the territorial to the tolerant of conspecifics and heterospecifics, and each strategy comes with its cost/ benefit balance. Holding and defending a solitary territory is a high cost strategy as it demands the investment of time and energy in patrolling and warding off intruders, and it also increases the risk of predation. It is still however a common strategy in many environments during breeding season due to its high return on investment within a particular set of conditions, as in the case of scarce and patchily distributed food supplies. It is also more beneficial when considering the importance of completing a successful breeding season, as some short lived birds live through only one, making brood defence the first priority. The same strategy however might not be feasible under different conditions, especially during the non-breeding season. For example when resources are abundant and evenly distributed, or when they are ephemeral or constantly moving, holding a territory in that case does not increase the odds of survival. Therefore, considering the environment, the bird’s life history stage and the resource being defended will aid in better understanding of the decisions and strategies being adopted in a given setting. Many Palearctic songbird species that breed in Denmark spend their non-breeding season in the Sahel region in Africa. This group of migrants has been experiencing population decline in

9 recent years and understanding the reasons behind such decline is difficult due to the lack of data on their winter ecology. In this study we look at the space use strategies of two Palaearctic migrant species that winter in Senegal, how they associate and whether or not - and to what extent - they defend a feeding territory.

Why study birds on their winter ground Migration in wild animal populations is a seasonal movement between two - or more – geographically separate habitats (Rappole, 2013). It can be distinguished from dispersal because of the difference in scale and repeatability. It is believed by some researchers to have evolved as a form of dispersal in response to competition for limiting resources including food and mates (Ricklefs, 1973). Billions of migrants of many bird species winter in the African tropics every year, many of which are passerines (Moreau, 1972), and while the breeding season ecology of many is well studied, little is known about their winter ecology in comparison. There are multiple lines of evidence that migratory behaviour is controlled by genetics in many of its aspects, causing some populations of the same species to winter on separate ranges in what is known as migratory divide (Helbig, 1991). This has significance when attempting to understand local population trends, as divergent wintering ranges and their conditions will result in different local trends on the breeding ranges. The current trends of population declines observed in some passerine songbird species are not fully understood due to the limited knowledge of the respective winter sites of each population. The available tracking technology does not allow for precise, real-time tracking of small sized birds, causing the knowledge of their life out of the breeding season to be primarily based on ring recoveries and tracking via light loggers, and in turn making the research of these species more labour intensive and the knowledge of their life histories to lag behind that of larger species. Studying the winter ecology on site is one way to elucidate the unknown aspects of migrant life histories. Several studies have shown a negative correlation between poor conditions on the non- breeding range and key aspects of migrants’ survival and reproduction, including body condition during the winter season and pre-migratory fattening, the date of departure on spring migration, survival en route and the percentage of migrants that attempt to breed upon arrival on the breeding range (Zwarts et al, 2009). In addition to its importance for conservation, studying winter ecology provides a complete picture of the dynamic interaction of a bird with the changes

10 in its environment during an annual cycle and would shed a light on how adaptations to such changes evolve. The aspect of winter ecology we are most interested in for this study is sociality; how birds associate with conspecifics and heterospecifics or the lack of such association, how a bird uses its habitat in the presence of others and how that agrees or differs from its behaviour during the breeding season. Because birds out of their breeding season are released from the requirements of breeding, we find that two main factors influence the strategy of space use and resource harvesting on the wintering range; competition and resource distribution. Both of these factors are dramatically different between the breeding and wintering ranges for the Palaearctic passerines. In the following section we will consider the space use and association strategies relevant to our model species.

Sociality as an extension of space use strategies Animal sociality in general is motivated by different benefits, causing the social strategies adopted – by a given individual under a given set of circumstances – to vary depending on the life history stage. Generally, social aggregation incurs both benefits and costs. Associating with conspecifics – and in some cases with heterospecifics – is beneficial when it dilutes the risk of predation (Treherne and Foster, 1981) and confuses predators (Milinski, 1977). In some cases it also incurs foraging advantages, for example when aggregations signal a rich food source (Krebs, 1974) and when larger groups cooperate in tackling larger prey which one individual cannot (Kruuk, 1972). Additionally, associating in a group helps some animals with thermoregulation (Trune and Slobodchikoff, 1976) and when moving in groups, either flying or swimming, members of the group can share the energetic cost of going against a current of air or water (Weihs, 1973; Partridge and Pitcher, 1979) The disadvantages of sociality include increased competition for resources (Forrester, 1991), increased risk of contracting diseases (Hoogland, 1979), increased chance of competition for mates and increased cuckoldry (Bray et al, 1975), as well as increased chances of inbreeding (Faulkes and Bennett, 2001). During the breeding season, animals, including birds, associate with conspecifics in order to find mates and reproduce, and this goal dictates other strategies like those concerned with space use and resource defence. During other stages, these strategies will differ as the goals and benefits

11 change. The first priority of a bird outside the breeding period will mainly be its survival, and its behaviour will change to achieve that end. Survival on the wintering grounds is determined by the success in finding and harvesting adequate resources, as well as escaping predation. The strategies that a bird employs to achieve both goals will vary according to the distribution of food supplies, the competition over those supplies, and presence of predators (Recher and Recher, 1969). Migrants, notably to Africa, join the resident species during a season of progressively decreasing food resources (Rappole, 1995) which results in both inter and intra-specific competition for food. If the energy spent defending a foraging territory is less than the energy gained from keeping it, territoriality would be a feasible strategy, and if the opposite is true then co existing with conspecifics/heterospecifics is a better strategy (Brown, 1964). When food supplies are patchy and far in between, keeping a territory is the suitable strategy as such a patch of resources is defined and defendable, while food supplies that are ephemeral and/ or constantly moving are not defendable (Brown, 1964) . Added to the cost of food harvesting, solitary birds are more vulnerable to predation compared to group foragers (King and Rappole, 2000).

The two Palaearctic songbird species we are concerned with in this study winter in the west part of the Sahel region in Africa. The Sahel is important to the Palearctic - Afrotropical migratory system because it is the first area that offers food to a southbound migrant after crossing the Sahara, and the last that offers it to a northbound one. Most migrants arrive in Sahel in September. Around this period the rainy season has come to an end and food supplies are abundant, but they start declining from that point onwards (Newton, 2008), however, despite appearances of decline, food supplies can still be found in some forms. As most of the dominant forms of vegetation are evergreen they continue to support insects and produce flower and fruits during the dry season. Therefore, around one quarter of the migrants in the Sahel do not move further south, including some Sylvia species that are also opportunistic frugivores (Pearson and Lack, 1992). Other species stay in the Sahel zone for the first couple of month of their migration season then move further south. Because food supplies decrease steadily during winter or occur in temporary flushes, the migrants joining that community need to be adapted to that environment in order to survive. There are several hypotheses regarding how the birds, both resident and migrant in the Sahel achieve this survival. In the case of specialists, adaptation to the local food sources and their distributions is believed to have evolved, while for generalists the mechanism is believed to be foraging flexibility by 12 using different prey type/ foraging technique and having broad niches. The niche breadth is particularly notable in the species that breed in forest habitats, which are reported to utilise a variety of habitats during winter, including open woodland, scrub, grassland and agricultural lands (Leisler, 1992). It was also found that while resident species that breed during the northern winter will stay within their territories migrants tend to be more itinerant, in pursuit of the temporary food supplies that cannot be exploited by resident species (Sinclair, 1978; Leisler, 1992) Many passerine migrants are insectivores, but are also opportunistic nectar and seed feeders. Insects are normally more abundant during the wet season, but are to be found in temporary abundance during the dry season as well due to the asynchrony in the fruit and seed production of local flora (Newton, 2008). Similarly, standing water offers hot spots of temporary insect abundance, offering critical food source for both inbound and outbound migrants (Wanink & Goudswaard, 2000). During periods of insect shortage, many passerine migrants supplement their diet by feeding on nectar and fruits. In addition to the opportunistic utilisation of alternative prey types, the dietary needs of migrants in Africa are lower in the non-breeding season than their levels in breeding season due to the decreased need to maintain body temperature through increased food intake, as well as the absence of energy demands of breeding and raising their young (Moreau, 1972). Finally, in some partial migrants, including P. collybita, some studies showed the individuals migrating further south of the range in the sub-Saharan region to be the older and of larger body size (Moreno-Opo et al, 2015) indicating that experience and knowledge of the habitat, along with better bodily condition, enable the individual to take longer migratory trips and survive in the more competitive environments. When considering the strategies adopted by migrants at different stages of their annual cycles, we find that those strategies differ between breeding and non-breeding seasons in many species, allowing them the flexibility of utilising the different habitat types. During breeding season, a myriad of birds keep a territory that is used for both nesting and raising young, as well as foraging. The size of territory used for nesting differs from that used for foraging. On their non breeding region, birds employ a number of strategies that range from solitary to flocking behaviour and from aggression to tolerance. Winter territoriality has been documented in around 75 species - most of which are new world warblers - and probably is adopted by many more unstudied species (Rappole, 1995). The strategy entails taking residence in, and defending a territory as an individual or in a flock. The period of resource defence can vary greatly 13 depending on the stability of that resource; ephemeral resources are defended short term (Armitage, 1955; Kale, 1967; Recher and Recher, 1969; Emlen, 1973), while stable resources are defended long term and even for the full winter stay (Eaton, 1953; Salewski et al, 2000). Winter site fidelity has been reported in some species between years (Kelsey, 1989) while others move from one short term territory to the next (Jones, 1998; Moreau, 1972). A territory is defended using a variety of methods, including physical displays and vocalisation (Rappole, 1988). Vocalisation is considered the cheaper alternative as it incurs no risk of injury, with short calls being cheaper to produce compared to song (Catchpole & Slater, 2008: 5 -113). Approach, chases and attacks are escalations that puts the territorial individual in increased risk of injury and are used in varying frequencies, making territorial behaviour a gradual one with varying associated cost. Another strategy is being solitary, non-territorial wanderer, where the migrants utilise seasonal resources in a given area while they are abundant, before moving further to more stable habitat patches (Jones et al, 1996). Confirming such foraging behaviour requires monitoring the migrant during the full winter season. Moreau (1952) and Morel and Bourliere (1962) have studied several species that winter in the Sahel region and adopt this strategy at least during the first period of their winter. Many of those birds move further south later in the season, where food sources are more stable (Jones, 1995; Jones et al, 1996) The third strategy is forming conspecific flocks, where individuals of the same species form flocks that last for the whole wintering season, foraging and fending off predators as one unit. This strategy is believed to be adopted when resources distribution is clumped and far in between (Taylor, 1984) as in the case of many seed and fruit eaters. Single species flocks tend to cover a large home range, sometimes shifting to new areas together (Witmer et al, 1997). the last known strategy is forming mixed species flocks, where individuals as few as one of each species associate in a multi-species flocks that last for varied lengths of time from hours to several months, foraging as a unit within a defined home range and defending it against other flocks (Rappole, 1995). Little is known about how these flocks are formed and maintained, and they are believed to serve a similar purpose to that of the single species flocks, i.e. resource defence and predation avoidance (Rappole, 2013). Few studies have demonstrated that within the same species, some individuals might adopt the strategy of solitary, itinerant non territoriality, while others would be territorial and defend a restricted home range (Rappole and Warner, 1980; Rappole et al, 1989, Rappole 1995). In addition to this variation within the same species, it is also known that some individuals will

14 adopt different strategies within the same season or the same day, depending on the distribution and abundance of food resources (Recher and Recher, 1969; Rappole, 1995)

The winter strategies of the two species: what is known so far?

The species:

Common Chiffchaff (Phylloscopus collybita): The main focus species for this study is a small (6-10 g) insectivorous passerine songbird that breeds in the boreal, temperate and Mediterranean forests and winters in the Afrotropics. The majority of the populations are migratory with few that are sedentary, making the species a partial migrant. There are multiple races and the one we are most concerned with in this study is nominate collybita, the race that breeds in Western Europe. The wintering range in Africa extends throughout the Sahel -Sudan region, from the West south of the Sahara starting at Senegal through southern Mauritania, Mali and Southern Niger. Main food source is insects of various genera, consists mostly of aphids (Hemiptera), flies (Diptera), beetles, adult and eggs of Lepidoptera and Psyllidae, and to much lesser frequency feeds on Hymeoptera and spiders. Insect prey size was found to be mostly of 2-4 mm body length when examining the items found in the faeces of migrants in western France (Bibby and Green, 1983). The species would also feed on some plant material when insects are in shortage; those include seeds and berries (summarized in Cramp and Perrins, 1992), and is also reported to be an opportunistic nectar feeder (Rodriguez and Valido, 2008)

Breeding season:

Habitat: Prefers forests of comparatively open canopy, and dense, tall undergrowth (Simms, 1985). Distribution is believed to be affected by interspecific competition, and habitat structure is more vital than vegetation when choosing a home range; the species prefers larger areas with clearings and roads, which in turn means moderately open canopy and taller, thicker undergrowth.

Sociality: During breeding season, known to be solitary and territorial, but can be found in high density (Price, 1935). Territory overlap also varies between populations Sæther, (1983) reported

15 minimal overlap of 2.6% in Gauldal, Norway, and Treuenfels, (1938) reported more dispersed population with non-contiguous territories in Damerow, Germany. As soon as they return to their breeding range, Chiffchaffs start establishing territories. Agonistic behaviour is most pronounced leading to and during pair formation and copulation periods, this includes chasing and attacking intruders (Rodrigues, 1996). In autumn, there are reports of the adults who are still in their territories attacking passage birds (Homann, 1960), the territory owner will warn the intruder with a rattle call before attacking. It is typical in autumn, however, for birds to tolerate each other with sporadic aggressive behaviour (Homann and Gwinner, 1963). Female aggression is largely in defence of young, and is directed at conspecifics and heterospecifics alike if they approach her nest (Howard, 1907-14; Homann, 1960). Other displays of aggression include wing and tail flicking, wing shivering, bill snapping and spasmodic song (Howard, 1907-14) reported more often at the end of the breeding season. These can also be signs of excitement and not necessarily a predictor of aggression (Jouard, 1934; Treuenfels, 1937). Cramp and Perrins (1992) made a distinction between highly defended nest area - radius of around 20 m - and the much larger feeding range. One study found male home ranges to be around 12 times bigger than the average nest area, and even reached 14 times bigger during the period of maximum density. These home ranges overlapped quite considerably, sometimes extending into the nest areas of other individuals. Same study reported female home ranges to be even bigger (Ferry et al, 1981). It is also established that several individuals will feed in a common areas outside of their nest territories when a temporary food source is available (summarised in Cramp and Perrins, 1992 ; Price, 1935, Gwinner, 1961). Nest territory is normally defended by the male until the young have fledged, but in some cases later than that. Females also defend the nest territory once the eggs hatch. The nest territory is typically used for courtship, copulation and building a nest, as well as foraging by the female to feed her young. No reports of flocking during the breeding season, but will tolerate other conspecifics and heterospecifics (Penn, 1936, Geissbühler, 1954) Similarly, no proof of flocking was found during moult, autumn migration (Geissbühler, 1954) nor spring migration and upon returning to natal grounds (Kowalski, 1957; Piechocki et al, 1982) the studies that have reported minor flocking after spring migration explained the behaviour by the availability of a food source Before autumn migration, reported to forage in fluid groups of both single and mixed species, where birds forage independently close to each other. This tendency to associate with 16 heterospecifics decreases during moult (Homann, 1960; Homann and Gwinner, 1963). The previous reports of breeding season association and territoriality suggest that the main function of territorial behaviour during that period is to defend the brood and not the feeding territory

Vocalisation: it has been established that male song is used for advertising territory and for mate attraction. On breeding grounds there are some reports of brief singing before choosing a territory (Geissbühler, 1954). Singing starts at arrival and lasts until July, then stops during moult between July and August, after which it resumes again in September-October (Prenn, 1936; Witherby et al, 1938). Rodrigues (1996), reported the singing intensive period to start at territory establishment and last post the female fertile period, and suggested song to function for warding off intruders as well as for communicating with the female. Song duels are reported but more common early in the breeding season (Homann, 1960) with singing rate decreasing after pair formation (Brown and Smith, 1982). . Playback of conspecific song has varied effect on territorial birds, including searching flights, diving approach and agonistic song, in other cases short song fragments with wing flicking, wing shivering or tail waving/flicking (Schubert, 1971)

Non breeding season: Habitat: In West Africa, is found in areas of Acacia nilotica and overall damp habitats, found as well in stretches of willows and Avicennia mangroves. Ring recoveries suggest winter site fidelity (Lack, 1986), which was reported in southern Spain (Herrera and Rodriguez, 1979; Finlayson, 1980), as well as Senegal (Morel and Roux, 1966) Reported to forage closer to the ground in winter (Alexandre, 1951b), by gleaning both in flight and while hovering (Prenn, 1936), our personal observations however do not confirm a tendency for foraging at a vegetation height different from that seen on breeding range, the birds foraged at heights relevant to the available tree cover.

Sociality: Individuals are reported to be solitary on wintering grounds; One study followed migrants throughout their stay in Egypt but reported no defence of territories (Simmons, 1954), similarly in Gibraltar (Finlayson, 1979a). Contrarily, some reported birds holding territories in Senegal from November to February (Morel & Roux, 1966). Some reports of aggregation exist; Herrera (1979).found the species to occur in small mixed flocks associated with other small passerines and other Phylloscopus warblers, Gaston (1970) 17 reported birds foraging in loose flocks of 5-20 birds, while others reported congregation of 30-40 birds on site with abundant prey in Cornwall (Penhallurick, 1978). Density on wintering grounds varied vastly between studies and regions. In Gibraltar, one study reported numbers of birds per km2 to vary from 9 to 224, depending on the habitat type (Anon, 1987).

Vocalisation: song is reported by multiple studies at many localities, including Kenya (Sessions, 1966) and India (Alexander, 1951), it occurs mainly between December and March. Also reported in birds wintering in Rome sang during autumn, then again from Mid-January until departure (Alexander, 1917). Similarly, birds wintering in England sang in November (Beckerlegge, 1951) and January (Hunt, 1948) Studies that followed ringed birds during autumn and the beginning of winter in Gernmany, noted singing in both adults and juveniles of both sexes, but no clear territoriality (Homann, 1960; Homann and Gwinner, 1963)

Subalpine Warbler (Sylvia cantillans): The second species investigated is a small (12 cm) old world warbler belonging to the Sylviidae family. The Western race, which is the nominate of the species, i.e. cantillans, breeds from the Iberian Peninsula in the west, through southern France to Southern Italy and Sicily in the east, and winters in Africa along the south of the Sahara; the wintering range is from Southern Mauritania in West Africa, through Senegal until The Gambia, but not recorded further to the south. The range extends through Mali, Niger, North Nigeria and Chad (Lamarche, 1981; Elgood, 1982; Newby et al, 1987). Races are reported to overlap throughout their wintering range (Morel and Roux, 1966). Breeding season in Southern Europe starts early April and ends around late June (Beven, 1967), Earliest arrivals at winter grounds in Senegal and Mali are mid to late August, and peaks in September (Moreau, 1961; Morel and Roux, 1966) Spring migration starts in February, and peaks in March- April, lasting in some years until May (Morel and Roux, 1966). Return to the natal grounds at the north of the Mediterranean from mid March – in Spain and Southern France – and reaches the northern limits of its range in the Rhone-Alpes region around mid April (Leberton, 1977).

18 Main food sources include insects, both adults and larvae from various taxa including mayflies, crickets, Hemiptera (Aphids), Lepidoptera such as moths, ants and beetles. Feeds mainly on fruits and seeds later in the summer and in the autumn when insect prey is scarce (Summarised in Cramp and Perrins, 1992). Feeds in scrub, but is also known to feed in the foliage of oaks and olive trees (Beven, 1967). Foraging behaviour on wintering grounds in Sudan was described to be by probing bill into acacia flowers, and in Senegal by gleaning insects off acacia flowers high in the tree canopy (Morel and Roux, 1966). Migrants passing through Libya were reported to feed on the ground among thistle bushes (Stanford, 1954). This variation suggests foraging behaviour to depend largely on the available type of food resource

Breeding season Habitat Preferred habitat type in both breeding and winter seasons is open scrubland. Found during breeding seasons in tree cover including holm oak Quercus ilex , and kermes oak Quercus coccifera.

Sociality: Known to be solitary and territorial during the breeding season, but high density is common. One study reported more than 28 territories per km2 in northern Portugal (Mead, 1975), while others found average density to be 91-120 pairs per km2 in the Camargue (Cody and Walter, 1976). Territories typically are used for courtship, nesting and rearing the young, although reports of feeding hundreds of meters away from the nest do exist (Trouche, 1946). Another study recorded the density at the end of the breeding season (August - September) in Spain to be between 30-50 individuals per km2 (Jordano, 1985). Agonistic behaviour is not thoroughly studied. Aggression towards conspecifics is reported on spring migration, albeit brief - chasing- and accompanied by what the author described as subsong (Simmons, 1954).

Vocalisation: Song is used for territorial defence, preceded by accelerated series of tick calls. Similar in general structure to the songs of other Sylviidae, notably common whitethroat Sylvia communis. Subsong is described and reported to be used in autumn and spring during passage aggressive displays (Simmons, 1954). The use of the term “subsong” could, however, be

19 inaccurate, as the latter usually serve no function (Dabelsteen et al, 1998), contrary to our findings (see the article section of this report) Several types of calls are described, including contact -alarm and alarm calls, tick calls, which are given singly or in series of accelerating ticks when the bird is excited or producing an alarm signal (Prodon, 1979). Reports of song duels during breeding season exist (Blondel, 1969), as well as agonistic displays. Interspecific aggression is also reported between Sylvia cantillans and Sylvia atricapilla (Cody and Walter, 1976). Singing starts upon arrival on the breeding grounds, and the intense singing period starts at the end of March/beginning of April and continues until the end of June (Witherby et al, 1938) Subsong was reported in autumn and spring (Simmons, 1954). Scattered reports of winter song exist; in Algeria and in Nigeria (Cramp and Perrins, 1992 ) Singing is commonly from cover in scrub or at lower levels in trees (Beven, 1967), although it is also known to sing in an open position or in flight. Song perch is typically at low height above ground.

Non-breeding season Habitat: On wintering grounds – in the Sahel region – found in acacia scrub, as well as gardens and smaller hedges, also in mangroves Avicennia, and in reeds Phragmites in Mali (Lamarche, 1981). Was also reported to use tamarisk Tamarix and olive Olea, for feeding while migrating through North Africa (Monk and Johnson, 1975). Reports of between-years winter site fidelity in Nigeria, where ringed birds were recaptured the following year at the same sites (Sharland, 1969), also in Senegal (Morel and Roux, 1966; Moreau, 1972)

Sociality: In winter, occurs in much lower density of only 2-3 individuals per km2 in Mauritania (Browne, 1982) but is also known to aggregate at much higher density – thousands at one site – where resources are abundant (Lamarche, 1981)

Vocalisation: No reports on winter song to our knowledge.

20 Space use strategies in two Palaearctic songbird migrants in winter: Patterns of territoriality, association and vocalisation in the Common Chiffchaff and Subalpine Warblers wintering in Northern Senegal.

Abstract

Migrant birds spend their lives on geographically separate and dramatically different habitats, on each of which they have different priorities and undergo different life history stages. Hence, the decisions governing their social and ecological behaviour at each locality are expected to be different. We investigated the space use and association strategies in the Common Chiffchaff Phylloscopus collybita and the Subalpine Warbler Sylvia cantillans, two Palaearctic migrants that winter in northern Senegal, using radio telemetry and playback experiments. Spontaneous singing was absent in Chiffchaffs during the period of observation, which ran from the end of February to the end of March 2017 and coincided with the end of their winter stay and was about a month before the departure of Subalpine Warblers. We found no evidence for flocking or association with conspecifics in P. collybita; no clear pattern of territoriality was observed either in the response to conspecifics song. Contrarily, S. cantillans showed clear and consistent territorial response to playback in the majority of the measured parameters; the species also had comparatively smaller home ranges with less degree of overlap compared to Chiffchaffs. These results show two different space use strategies, solitary non-territoriality for P. collybita and solitary territoriality for S. cantillans. It is important to note that these results represent only the end of the non-breeding season; further conclusions about the duration of these strategies require longer monitoring

Introduction More than 200 species migrate from the Palaearctic to the Afrotropics every year (Moreau, 1972), spending the larger bulk of their lives away from their breeding range. Of these species there are big numbers of small passerine songbirds, the migration of which is more enigmatic due to their short lifespan, their small sizes and the cryptic morphology and behaviour of many. The breeding season ecology of most of these species is well studied, but very little is known about their winter ecology. understanding the dynamics of habitat utilisation and the interaction with the community on the wintering range, as well as the migrant’s response to changes there and en route, are all relevant to understanding the life history of a migrant and to its conservation purposes. Passerine migrants to West Africa utilise habitats that are different from those found on their breeding range, and if the species belong to the same guild competition is expected to appear (Huston, 1994) as the number of individuals bred each year in the Palearactic is expected to be larger than the number that can be sustained by the wintering range (Rappole, 2005). Despite the expected competition between conspecifics, and between heterospecifics utilising the same food source and/or using the same foraging strategies, research has shown space use strategies to vary within some of the avian species between populations, between localities, and within season (Scordato, 2017) We studied two passerine species wintering in northern Senegal 21 to compare their space use strategies. The Common Chiffchaff (Phylloscopus collybita) and Subalpine Warbler (Sylvia cantillans) are songbirds that breed in the Palaearctic and winter in the Afrotoropics. Both species are known to be solitary and territorial during the breeding season, although the strategy is nuanced and changes in intensity during the season. In this study we investigate the space use strategies of the two species on their winter range using tracking data and playback experiments.

Materials and methods

Study site Both the tracking and playback experiments were conducted at the Djoudj national park in northern Senegal. The data collection site is an open mixed habitat of open forest and scrubland situated along a tributary of the Senegal River at the north of the park. The habitat is dominated by Mesquite Prosopis juliflora and Tamarisk Tamarix senegalensis, along with lower density of Nitraria retusa shrubs, all of which are adapted to the high soil salinity found in the region. The tracking and Playback experiments were performed at the area surrounding the Djoudj Biological Station, which is close to the villages found in the park. The area is regularly used by the inhabitants for collection of firewood and to access the river. Three areas – separated by at least 1 km2 in each direction – were cycled between for playback experiments to avoid habituation.

Radio tracking Radio telemetry was carried out during the period of 14-28 January, 2012. In order to determine home ranges and their overlap percentages, birds were tracked during 4 – 12 days each (Chiffchaff: 10 individuals, average number of days = 10, average relocations = 30; Subalpine Warbler: 5 individuals, average number of days = 9, average relocations =26) Each bird was fitted with 0.31g lightweight radio transmitter glued to the back, expected battery life of 3 weeks (Holohil systems Ltd.). Tracking was done using a handheld VHF receiver (AOR8000) and a directional 3-element Yagi antenna. Each bird was located at least twice and up to four times a day, and relocations were separated by at least one hour to avoid spatial correlation.

22 Playback experiments High quality Chiffchaff and Subalpine Warbler songs were downloaded from Xeno-canot (http://www.xeno-canto.org). The recordings were filtered in Avisoft SASLab (Avisoft Bioacoustic, Berlin, Germany) using the FIR filtre (band bass: 1 – 4 kHz) filter to remove sounds outside of the song frequency range for each species. The recordings were then normalised to 90% of maximum amplitude. 10 recordings per species were rotated between trials to avoid habituation through eavesdropping among the individuals in neighbouring areas. Playback experiments were carried out during the period between February 21st and March 19th, 2017. Trials were performed from 7 in the morning until midday and from 16:00 hrs until sunset as these were the two periods of the day during which the birds were most active to avoid the midday heat. A speaker was hung from a tree branch approximately 1 m above ground and was connected to an MP3 player by a long cable to allow for remote initiation/termination of playback, the observer was always between 10-15 m away from the speaker in plain sight, but sudden movement was avoided. The following categorical responses were noted (Approach, wing flicking, calling, singing, chase) the degree and time duration of each response: (approach distance: the closest the bird came to the speaker during the whole trial, approach latency: number of minutes before the bird came to the closest distance from the speaker, approach duration: the number of minutes the bird spent at the closest distance it came to the speaker, retreat: the number of minutes before the bird retreated from the closest distance it came to the speaker, flicking duration: the number of minutes during which the Chiffchaff showed increased wing flicking, minutes to leaving the site: the number of minutes before the bird left the experiment site altogether, call latency: the number of minutes before the bird started calling, call duration: the number of minutes before the bird stopped calling, song latency: the number of minutes before the bird started singing, song duration: the number of minutes before the bird stopped singing). The number of birds spotted in the same tree or in adjacent trees – not further than 25 m from other individuals – was also recorded. Vocal responses were recorded in the case of Subalpine Warblers but not for Chiffchaff, as the latter did not vocalise. For Chiffchaffs, trials were initially non targeted, but with the obvious decrease in their numbers the method was later changed so a focal bird was first located in and observed for at least 2 minutes before starting the playback. The bird continued to be observed during a playback period of 5 minutes, after which the playback was terminated and the bird continued to be watched for at least 2 more minutes if it was still on site. The results for both targeted and random trials were

23 pooled for the analysis after a Chi-square test showed no significant different in all pairwise comparisons of the categorical response parameters collected. For Subalpine Warblers, all playback experiments were not targeted as pilot trials showed high percentage of response – mainly approach – when the speaker was placed at random locations. Following the random selection of a speaker position, the surrounding area was observed for 2 minutes while recording to establish a baseline for control levels of any existing vocalisation. Following the initial 2 minutes, the playback was started and the recording continued for the 10 minutes duration of playback, followed by 3-5 minutes of post playback recording to establish return to baseline levels of vocalisation.

Statistical analyses Space use: Home range sizes and overlaps were performed in R Studio 3.3.1 – (R Development Core Team 2016)., using the adehabitatHR data package (Calenge, 2006). For this calculation we only included the individuals with at the total of at least 10 relocations, total of 16 birds (11 Chiffchaffs, 5 Subalpine Warblers). For actual number of relocations for each individual, see table 2 and 3 in the appendix. We calculated home range sizes using 90% and 50% bivariate normal fixed kernel densities (KD), with href reference for estimating the smoothing factor (Worton 1989; Worton1995). We also calculated home range sizes using 90% and 50% minimum convex polygon (MCP) for comparison. To measure territoriality, we calculated home range overlap of the 90% and 50% KD, measured as the proportion between overlap area and an Individual’s full home-range area, large overlaps indicate tolerance of conspecifics We also calculated two additional indces; PHRi,j, which represents the probability of an individual being in the home range of another conspecific, by using the utilisation distributions of the kernel densities (Fieberg and Kochanny 2005). The second index UDOI represents the utilisation of the overlap area, if the value of the index is > 1 then the utilisation of the overlap area is more than expected in the case of uniform space use, while a value < 1 indicates the utilisation of the overlap area to be less than the expected in the case of uniform utilisation. The means of calculated indices (KDE 90 & 50 area and overlap, PHRi,j and UDOI) for the two populations were compared using a two sample t-test assuming unequal variance and the corresponding P-values were noted.

24 Association Patterns of association were investigated by performing a bootstrap test in Excel. Pairwise association was tested by calculating the distance between each pair of birds relocated within an hour of each other and finding the average distance for each pair. The coordinates for each relocation used were resampled (1000 permutations × the number of actual paired observations) to create a distribution of random distances, the average distances calculated for each pair was then compared to the mean of the random distribution created using their unique coordinates in order to find out whether the former were significantly different from the average of their respective random distributions. A bonferroni correction was performed to correct the α values based on the number of tests performed for each pair. To determine whether the distance calculated between each pair correlates to the time that elapsed between the two relocations used in calculating that distance, we modelled the relationship between time and distance using linear regression with time as a predictor and found the correlation coefficient for each time/distance pair.

Response to Playback Because some of the experiments were targeted and others were random, the five categorical responses (presence/absence of behaviour) were initially divided into those two groups and a Chi-Square test was performed to ensure they were not different. The results were all insignificant at a P = .05. Accordingly, the random and targeted observations were pooled for analysis. The categorical response parameters representing the presence/absence of a response (approach, wing flicking (Chiffchaff), call, song, chase (of conspecifics when present)) were scored to demonstrate the percentage showing a response in each species. Because wing flicking is only found in Chiffchaffs, we decided to exclude it from the main results. We also used species as predictor in a logistic regression to model the approach probability using a general linear model in R. Of the fraction that approached the speaker, the means of the all the continuous response variables describing approach were compare for the two species using a two sample t-test assuming unequal variance, the variances were compared a priori and were found to be unequal. For the other categories we measured duration and latency, but since only one species exhibited those responses (call, song, chase), we did not use the measurements in the analysis.

25 Results Do the two species have similar home sizes and overlap? Table 1 – home range sizes in km2 and overlap percentage for the two species ± the standard deviation from the mean, and the P-value of the two tailed, two sample t-test assuming unequal variance comparing the respective means. index Phylloscopus Sylvia t-test p-value collybita cantillans 95% MCP area (Km2) 0.016±0.018 0.005±0.008 0.1 50% MCP area (Km2) 0.004±0.006 0.002±0.004 0.3 Mean 90% KDE area (Km2) 0.05±0.05 0.016±0.02 0.09 Mean 90% KDE overlap 33.3±15.3 16.4±18.5 0.1 Mean 50% KDE area (Km2) 0.014±0.15 0.004±0.006 0.09 Mean 50% KDE overlap 15.2±6 5.4±10.9 0.1 UDOI 0.13±0.07 0.02±0.02 0.0005 PHRi,j % 31.7±21 14.7±19 0.1

The two species differed in their home range sizes and the degree of overlap between individual home ranges. The mean 90% & 50% KDE area and overlap for P. collybita – Figure [1]– are larger than those of S. cantillans. – Figure [2] –. Mean 90% and 50% KDE areas were not found to be significantly different (P= 0.09 for both 90% and 50%). The comparison of Mean 90% and 50% overlap yielded values that are slightly larger than the significant value (0,05< P <.0.1 for both 90%, and 50%). The Mean 95% and 50% MCP area were calculated for both species and were not found to be significantly different (P-value = 0.1 for 95% and 0.3 for 50%) The means of UDOI were also compared found to be significantly different (P=0.0005), while the difference in the means of PHRi were not significantly different (P=0.1). Table [1] For individual home range sizes for both species, see table 3 and 4 in Appendix I.

26

Figure 1 – Chiffchaff individual home ranges and their respective overlap. Red (1), sky blue (2), aqua (5), lime green (9), magenta (10), black (14), dark green(15), white (16), yellow (19), dark blue (20), orange (21)

Figure 2- Subalpine Warblers individual territories and their respective overlap. Red (1), white (3), Aqua (4), orange (5), lime green (7)

Did chiffchaffs associate? The investigation of association patterns indicates a solitary strategy in Chiffchaffs. Bootstrap test results for the comparison of measured pairwise distances were found to be insignificant in 53 out of 55 pairs. A Benferroni correction was performed to adjust for increased probability of a

27 type 1 error with multiple tests, resulting in no significant distance for all 55 pairs. This shows no evidence of Chiffchaffs flocking with conspecifics. The investigation of correlation between the calculated pairwise distances, and the time gap separating the relocations used for measuring that distance, showed very weak correlation for all pairs (mean R2=0.06), this results does not support the assumption that the distance between each pair of tracked birds was affected by the time that elapsed between the two relocations. For full list of values see table [2] in the Appendix. Figure [3] shows the distribution of the distances between each pair tracked within an hour of each other, the majority of the pairs were separated by a distance between 125 and 175 meters, which does not indicate flocking nor association.

Figure 3- the distribution of average distances between the pairs of investigated individuals shown in meters.

Did the two species respond differently to conspecifics’ song? We expected aggressive response to be one or all of the following: approaching and attacking the speaker, as well as calling and/or singing back at the speaker. Increase in wing flicking in Chiffchaffs is also a sign of excitement/aggression in some contexts, and chasing off conspecifics when present on site during the playback.

28

Figure 4- percentage of individuals approaching the speaker, calling and singing at the speaker, and chasing conspecifics when present in both species (left : Phylloscopus collybita, right : Sylvia cantillans)

29 23% of playback trials (n= 69, 16 approached) for P. collybita resulted in the focal individual approaching the speaker, while 80 % of the S. cantillans trials (n=106, 85 approached) resulted in approach

The approach probability was modelled using species as a predictor in a logistic regression, and the probability of approach being affected by species was highly significant (Z= - 6.919, P = 4.55e-12)

20% of P. collybita trials (16 out of 69) resulted in increased wing flicking – See Figure in Appendix –. Not all the indviduals exhibiting this response did approach the speaker. This response does not apply in the case of S. cantillans as it is not a behavioural response observed in the species.

For the rest of the categorical responses measured, only S. cantillans responded vocally to playback. 64% of the trials resulted in calls (n=68, 4 of which did not approach the speaker), while 10% resulted in song (n=10, all of which approached the speaker and called).

39% of S. cantillans trials where conspecifics were present resulted in the focal individual chasing a present conspecific (n=13 out of 28, 2 of which did not call and one of which did not approach the speaker)

Figure 5-box plots representing the quantitative measures of approach to the speaker: approach distance, latency and duration, minutes to first retreat from the speaker, minutes before the birds left the site completely and group size represents the number of conspecifics observed on site during the trial. The figure represents only the subset of trials where the focal bird approached the speaker. The y axis is a scale, distance variables are in meters and time variables are in minutes. 30 Figure [5] shows the spread and median of the continuous parameters for the fraction of individuals that approached the speaker in both species.

Of that, the means of each of the continuous responses were compared for the two species with a two sample t-test assuming unequal variance. Three out of the five means were found to be signficantly different (Table 2)

Table 2 – mean values of the quantitative response parameters recorded for both species in reaction to playback of conspecific song, and the p-value of the two tailed, two sample t-test assuming unequal variance comparing the respective means.

Parameter Mean– Chiffchaff Mean– Subalpine t-test p- value Warbler Approach distance 5.9 ± 4.7 m 8.6 ±7.2m 0.07 Approach latency 3.8 ± 2.8min. 4.0±2.7 min. 0.68 Approach duration 3.03 ± 1.9 min. 4.2 ± 3.3 min. 0.05 Minutes to retreat from the speaker 1.4 ± 1.7 min. 2.8 ± 2.8 min. 0.02 Minutes to leaving the site 4.8 ± 4.2 min. 7.7 ± 4.4 min. 0.02

Overall approach distances and latency were shorter for P. collybita, while the duration of approach was longer on average for S. cantillans. A similar pattern is also seen in the number of minutes before the individual retreated from the closest distance of approach. Finally, the number of minutes before the bird left the site completely was longer on average for S. cantillans than P. collybita.

Discussion The winter strategies of the two studied species differed in space use and territoriality. Our data did not provide evidence of flocking, vocalisation nor winter territoriality in the Common Chiffchaff during the period right before their departure on spring migration; we have found however strong evidence of territoriality in Subalpine Warblers, shown primarily in their response to playback of conspecifics song and their tendency to have smaller home range sizes. During the period of the tracking, Chiffchaffs foraged over large home ranges that overlapped considerably and encompassed diverse tree cover. The utilisation of the overlap areas was significantly higher in Chiffchaffs compared to Subalpine Warblers as shown by the UDOI index. The lack of significant difference for the means of the other calculated indices could be caused by the small sample sizes (Chiffchaff n=11, Subalpine Warblers n=5). It is also worth noting that one of the tracked Subalpine Warblers had a home range that is much larger than those of the other individuals, completely encompassing the home ranges of two and overlapping with a third. This individuals would have been excluded as an outlier if the sample size was bigger. 31 Chiffchaffs foraged at different tree heights and showed no aggression towards conspecifics when present. Playback of conspecifics’ song did not elicit clear patterns of aggression, either through approach nor vocalisation, nor did it elicit immediate retreat from the playback site. The fraction of the tested individuals that approached the speaker exhibited fast and close approach, which on its own could suggest aggression, but when combined with the shorter time spent close to the speaker and fast retreat from it could mean that the first two measures simply signify excitement or investigation, followed by avoidance shown by the faster retreat, but not a complete escape as most birds stayed longer on site. It is also worth considering that the sample size of chiffchaffs that approached the speaker is small (n=16) in comparison to Subalpine Warblers (n=85)The sum of all these responses, in addition to the large home range, all point towards a non-territorial space use strategy. Contrarily, The Subalpine Warblers foraged over smaller home range size that overlapped to a lesser degree, and utilised the overlap areas at a significantly lesser frequency. Observation of foraging behaviour showed the species to consistently forage in Tamarisk shrubs, which are naturally low and less dense relative to the other trees on site. Playback of conspecifics’ song resulted in consistent approach and calling in the majority of trials, with most of the individuals tested staying on site for the whole length of the playback session. All evidence confirm that the strategy adopted by Subalpine Warblers is solitary territoriality, and that the commonest lines of defending the territory are in order: approach and scanning/calling, and to a much lesser degree singing and chasing intruders. Our findings for Chiffchaffs did not depart dramatically from the previous reports on their winter behaviour. Chiffchaffs are reported to be tolerant of conspecifics outside of the breeding period. For example, singing to ward off intruders is reported by many studies to be most intensive during the period of pair formation and copulation (Rodrigues, 1996), and territorial behaviour in general continues during incubation and brood care period but decreases greatly once it is over. The authors of the previous study suggested continued singing following pair formation to be for the purposes of territory maintenance and to contact the female during the brood care period. Once the brood has fledged, singing in general, and other territorial displays decrease dramatically and are absent in many contexts. Singing has, however, been reported outside of the pair formation and brood care period – Curry- Lindahl (1981b) reported singing in November upon arrival, Homann (1960) also reported singing during autumn- September to November – while Homann and Gwinner (1963) reported singing up to December in birds of all groups and both sexes while wintering in Germany, but reported no aggression towards conspecifics. Alexander (1951) also reported early morning 32 singing from birds wintering in Rome during autumn, after which the singing stops to commence again mid January until departure. None of these studies however quantified the intensity of singing nor reported it for the entirety of the winter season. Studies performed on Willow warblers, a close relative of the Chiffchaff, have also reported territory defence on winter range by approaching and attacking decoys during playback of conspecifics song – but no counter singing – (Sorensen, 2014) concluding Willow Warbler winter strategy to be single species group territoriality. These findings contradict with a myriad of other studies conducted on the same species. Salewski et al (2002) studied the territorial behaviour of Willow warblers wintering in the Ivory Coast and found no evidence of territoriality. The species reportedly did sing frequently upon arrival in November, and to a lesser degree during spring. They also reported the species to be itinerant and to join monospecific or mixed species flocks. The absence of a need to maintain a feeding territory in Chiffchaffs can be explained by their foraging behaviour and prey type. The species belongs to the guild of leaf gleaning insectivores, and are known to be flexible foragers that will switch to other prey type during periods of insect shortage. Chiffchaffs feed on aphids and small insects as reported by Simmons (1954), this type of prey is ephemeral as it occurs in short bursts, and cannot be defended as it occurs over large geographical areas. When the resource cannot be defended, territorial behaviour does not result in increased fitness (Brown, 1964). Prey type can also explain the lack of aggregation and flocking. Birds that forage in flocks do so when the food source is more efficiently harvested and defended in groups as in the case of seed and fruit eaters, while prey that is short lived, moving or easily harvested individually does not warrant group foraging. Regarding the absence of flocking, it is not surprising as aggregation increases competition for the already limiting food resources, and in some cases also increases the risk of predation when it signals the site of aggregation as a prey rich one. During a pre-migratory period, a migrant feeds more intensively to build up the body reserves necessary for undertaking the journey ahead. Intensive feeding reduces predator vigilance in favour of increasing feeding rates (Lindström, 1990) and although flocking diffuses the individual predation probability among the flock, in the case at hand it does not seem to balance the disadvantage incurred by increased competition and attraction of predator in the first place. Subalpine Warblers on the other hand are known to be solitary and territorial during breeding season, and sing for territorial defence. (Witherby et al, 1938). The species prefers thorny scrubland on its breeding range and is generally found in dense, low scrub (Beven, 1967). Simmons (1954) reported tolerance of conspecifics during spring, although chasing did occur in 33 conspecific flocks, accompanied by singing. Although singing can incur the cost of increasing the risk of predation, the singing observed during this study was what would be termed “soft song”. According to Dabelsteen et al (1998), soft song differs from subsong in that the latter is functionless, quieter version of full song, while soft song functions in aggressive and sexual context. Soft song is believed to have evolved to avoid detection by eavesdropping individuals in the vicinity, either conspecifics other the intended receiver or predators. Not much work has been done on the species’ winter territoriality, but it could probably be explained by its prey preference. Subalpine Warblers feed mainly on insects, but those are generally of larger size relative to the Chiffchaff prey. Observations recorded that prey consists of beetles and caterpillars (Witherby et al, 1938), moth (Armitage, 1930), crickets, spiders and stick insect, the latter of length between 1.5 -2 inches - (Beven, 1967). It is also reported to feed on Salvadora berries while wintering in West Africa (Bannerman, 1953). Our own observations noted Subalpine Warblers to be found primarily in the low shrubs of Tamarisk and Nitraria retusa, suggesting they defended a fixed food source. That agrees with the reports of the species feeding on fruits and berries, as Nitraria retusa was fruiting during the period of the study.

The disparity of strategies between the two species can also be caused by the type of habitat each utilises. Despite both species being habitat generalists, Subalpine Warblers were reported more often in dry scrubland (summarised in Cramp and Perrins, 1992), a habitat that offers lower density of invertebrate prey compared to wetlands, with individuals in scrubland having significantly higher body fat reserve, which is believed to be a strategic measure against starvation in birds inhabiting ranges with lower food supplies. Chiffchaffs were equally likely to forage in both dry scrubland and wetlands and showed no significant difference of body fat reserves between the two (Vafidis et al, 2014), although Morel and Roux (1966) reported that once passage period is over, Chiffchaffs avoided dry scrubland and mainly inhabited the open forest areas of Acacia stands, which on the study site were closer to the water. Vafidis et al (2014) found dry habitats to have around half the amount of invertebrate prey found in wetland habitats, which leads us to believe that Subalpine Warblers in that locality do not feed exclusively on insects, but supplement their diet during periods of invertebrate shortage with fruits, a resource that is defendable. Finally, it is worth noting that Subalpine Warblers depart on their spring migration about a month later than Chiffchaffs do. Chiffchaffs arrive on their breeding range in Europe between mid March and early April, while Subalpine Warblers spring migration peaks in March-April and can last until May (Morel and Roux, 1966). Prior to the commencement of playback 34 experiments in our study, captured Chiffchaffs in late February showed considerable degree of fattening, they also decreased in numbers and eventually left the site between late February and early March. Subalpine Warblers were still present in abundance and holding territories during the same period, confirming asynchronous migration timing between the two species and subsequently different dietary demands.

Conclusion Chiffchaffs showed no signs of territoriality, flocking nor defending food sources on their wintering ground in Senegal during the period directly before departure on spring migration (February – March), While Subalpine Warblers showed well defined territorial behaviour during the same period. These findings support the view that space use strategies are the result of a dynamic interaction between the species’ prey type, morphology and migration schedule among others, all of which are the result of the species’ evolutionary history and are therefore expected to diverge when comparing distantly related species.

35 References

- Alexander, C. J. 1917. Observations on birds singing in their winter quarters and on migration. British Birds xi, 98-102. - Alexander, H.G. 1951. Northern chiffchaffs and kindred Phylloscopi. Brit. Birds 44:358- 360 - Anon. 1987.Strait of Gibraltar Bird Observatory special report I. - Armitage, K. 1955. Territorial behavior in fall migrant Rufous Humingbirds. Condor 57:239– 240. - Bannerman, D. A. 1953. The Birds of the British Isles II. Oliver and Boyd. Edinburgh. - Beckerlegge, J. E. 1951.Winter song of Chiffchaff. British Birds 44 , 44-94 - Beven, G. 1967. Studies of Less Familiar Birds. 143. Subalpine Warbler. British Birds 60: 123- 129. - Blondel, J. 1969. Synécologie des passereaux résidents et migrateurs dans le Midi Méditerranéan Francais. Thèse Doct. État, C.R.D.P., Marseille. - Bray, O. E., Kennelly, J. J., and Guarino, J. L. 1975. Fertility of eggs produced on territories of vasectomised red-winged blackbirds. Wilson Bulletin 87, 187-195. - Brown, J.L. 1964. The evolution of diversity in avian territorial systems. Wilson Bulletin 76, 160-169. - Brown, R. G. B. 1963. The behaviour of the willow warbler Phylloscopus trochilus in continuous daylight. Ibis 105:63-75 - Brown, A.W and Smith, R W J 1982. Elusive Chiffchaffs. Scottish Birds 12, 87-88. - Calenge, C. (2006) The package “adehabitat” for the r software: A tool for the analysis of space and habitat use by animals. Ecological Modelling 197: 516–519. - Catchpole, C., & Slater, P. (2008). Bird Song: Biological Themes and Variations. Cambridge: Cambridge University Press. doi:10.1017/CBO9780511754791 - Cody, M. L. and Walter, H. 1976. Habitat Selection and interspecific Interactions among Mediterranean Sylviid Warblers. Oikos 27:210-238 - Cramp, S. and Perrins, C. M. 1994. The birds of the Western Palaearctic: Volume VI. Oxford: Oxford University Press. - Curry-Lindahl, K. 1981. Bird Migration in Africa I. Academic Press INC. London. - Dabelsteen, T., McGregor, P. K., Lampe, H. M., Langmore, N. E. and Holland, J. 1998. Quiet Song in Song Birds: An Overlooked Phenomenon. Bioacoustics 9, 89-105. - Eaton, S. W. 1953. Wood warblers wintering in Cuba. Wilson Bulletin 65:169– 174. 36 - Elgood, J. H. 1982. The Birds of Nigeria. British Ornithologists' Union. London - Faulkes, C. and Bennett, N. 2001. Family values: group dynamics and social control of reproduction in African mole-rats. Trends in Ecology & Evolution 16, 181-190. - Fieberg, J. and Kochanny, C. O. 2005. Quantifying home-range overlap: The importance of the utilization distribution. Journal of Wildlife Management 69, 1346–1359. - Finlayson, J. C. 1979. Movements of the Fan-tailed Warbler Cisticola juncidis at Gibraltar. Ibis 121: 487-489. - Finlayson, J. C. 1980. The recurrence in winter quarters at Gibraltar for some scrub passerines. Ringing & Migration 3: 32-34. - Forrester, G. E. 1991. Social rank, individual size and group composition as determinants of food consumption by humbug damselfish, Dascyllus aruanus. Animal behaviour 42, 701-711. - Gaston, A.J. 1970. Birds in the Central Sahara in winter. Bulletin of British Ornithologists’ Club 2 and 3:53-60, 61-66 - Geissbühler, W. (1954) Beitrag zur biologie des Zilpzalps, Phylloscopus collybita. Ornithologische Beobachter 51, 71-99. - Helbig, A. J. 1991. Inheritance of migratory direction in a bird species: a cross-breeding experiment with SE and SW-migrating blackcaps (Sylvia atricapilla). Behavioural Ecology and Sociobiology 28:9– 12. - Herrera, C M. and Rodriguez, M. 1979. Year to year site constancy among three passerines species wintering at a southern Spanish locality. Ringing & Migration 2: 160. - Herrera, C. M. 1979. Ecological Aspects of Heterospecific Flocks Formation in a Mediterranean Passerine Bird Community. Oikos 33, 85-96. - Homann, V.P. 1960. Beitrag zur Verhaltensbiologie des Weidenlaubsängers (Phylloscopus collybita). Journal für Ornithologie 101, 195-224. - Homann, V. P. and Gwinner, E. 1963. Zum Balzverhalten des Zilpzalps, Phylloscopus collybita, im Frühling und im Herbst. Journal für Ornithologie 104, 365-371 - Hoogland, J. L. 1979. Aggression, ectoprasitism and other possible costs of prairie dog (Sciuridae:Cynomys spp.) coloniality. Behaviour 69, 1-35 - Howard, H. E. 1907-14. The British Warblers. London - Hunt, O. D., 1948. Winter Chiffchaff Song. British Birds 41, 309. - Huston, M.A. 1994. Biological Diversity – the Coexistence of Species in Changing Landscapes. Cambridge: Cambridge University Press.

37 - Jones, P. 1995. Migration strategies of Palaearctic passerines in Africa: An overview. Israel Journal of Zoology 41, 393-406 - Jones, P., Vickery, J., Holt, S. and Cresswell, W. 1996. A preliminary assessment of some factors influencing the density and distribution of Palaearctic passerine migrants in the Sahel zone of West Africa. Bird Study 43: 73-84. - Jordano, P. 1985. The annual cycle of frugivorous passerines in southern Spanish Mediterranean shrublands: The wintering season and between-year variations. Ardeola 32: 69-94 - Jouard, H. 1934. Comment reconnoitre, dans la nature, nos quatre pouillots. Alauda 6, 479-502 - King, D. I., and J. H. Rappole. 2000. Mixed-species foraging flocks in montane pine forests of Middle America. Condor 102:664– 672. - Kowalski, S. 1957. Le Pouillot véloce (Phylloscopus collybita) sédentaire en Loire- Atlantique. L'Oiseau et R.F.O. 27: 385-386. - Krebs, J. R. 1974. Colonial nesting and social feeding as strategies for exploiting food resources in the great blue heron (Ardea herodias). Behaviour 51, 99 – 134. - Kruuk, H. 1972. The Spotted Hyena. Chicago, Chicago University Press. - Lack, P. C.1986. The atlas of wintering birds in Britain and Ireland. Calton. Academic Press Inc. - Lamarche, B. (1981) Liste commentée des oiseaux du Mali. Malimbus 3: 73–102. - Leberton, P. 1977. Atlas Ornithologique Rhone-Alpes. Centre ornithologique Rhône- Alpes, Université Lyon I. - Leisler, B. 1992. Habitat selection and coexistence of migrants and Afrotropical residents. Ibis 134 (suppl.1): 77-82 - Lindström, A. 1990. The role of predation risk in stopover habitat selection in migration Bramblings Fringilla montifringilla. Behavioural Ecology 1, 102 – 106. - Mead, C. J. 1975. Observations on the bird communities of three sites in north and west Iberia. Ardeola 21: 699-732. - Milinski , M. 1977. Experiments on the selection by predators against spatial oddity of their prey. Zeitschrift für Tierpsychologie 51, 36-40. - Monk, J. F. and Johnson, E. D. H. 1975. Palaearctic bird migration in the Northern Algerian Sahara, spring 1973. Ardeola 21:875-902. - Moreau, R. E. 1952. The place of Africa in the Palaearctic migration system. Journal of Animal Ecology 21:250– 271. 38 - Moreau, R. E. 1961. Problems of Mediterranean-Saharan migration. Ibis 103a: 373-427. - Moreau, R. E. 1972. The Palaearctic-African bird migration systems. Academic Press, New York. - Morel, G., and Bourlière. F 1962. Ecological relations of the sedentary and migratory avifauna in a Sahel savannah of lower Senegal [in French]. Terre et Vie 4:371– 393. - Morel, G and Roux. F. 1966. Les Migrateurs Paléarctique au Sénégal II. Passeraux et synthèse générale. Terre Vie 20: 19-72. - Moreno-Opo, R., Belamendia, P. V., Onrubia, A., Monteagudo, A. and de la Puente, J. 2015. Differential migration in the Common Chiffchaff Phylloscopus collybita: Sub- Saharan wintering grounds host more adults and females as well as birds of larger size and better physical condition. Ardeola 62, 237-253. - Newby, J. Gretteberger, J. and Watkins, J. 1987. The Birds of the Northern Aïr, Niger. Malimbus 9:4-16 - Newton, I. 2008. The migration ecology of birds. Academic Press, London. - Penhallurick, R. D. 1978. Chiffchaffs wintering at sewage works in west Cornwall. British Birds 71, 183-186. - Partridge, B. L. and Pitcher, T. 1979. Evidence against a hydrodynamic function of fish schools. Nature 279, 418-419. - Pearson, D. J. and Lack, P. C. 1992. Migration patterns and habitat use by passerine and near-passerine migrant birds in eastern Africa. Ibis 134 (suppl1): 89-8. - Piechocki, R., Stubbe, M., Uhlenhaut, K., and Sumjaa, D. 1982 . Beiträge zur Avifauna der Mongolei. Teil IV. Passeriformes. - Mitteilungen aus dem Zoologischen Museum in Berlin. 58, Suppl.: Ann. Ornithol. 6: 3-53. - Prenn, F. 1936. Beobachtungen zur Lebensweise des Weidenlaubsängers (Phylloscopus collybita Viell.).- Journal für Ornithologie. 84: 378-386. - Price, M. P. 1935. Notes on population problems and territorial habits of Chiffchaffs and Willow Warblers.British Birds 29, 158-166. - Prodon, R. 1979. Les critères auditifs des detection et de determination des Fauvettes Méditerranéennes. Le Bièvre 1: 45-52. - Rappole, J. H. 1988. Intra and intersexual competition in migratory passerine birds during the nonbreeding season. Proceedings of the International Ornithological Congress 17:2308– 2317. - Rappole, J. H. 1995. The ecology of migrant birds: A Neotropical perspective . Smithsonian Institution Press, Washington, DC. 39 - Rappole, J. H., and D. W. Warner. 1980. Ecological aspects of avian migrant behavior in Veracruz, Mexico. Pages 353– 394 in Migrant birds in the Neotropics: Ecology, behaviour, conservation, and distribution (A. Keast and E. S. Morton, eds.). Smithsonian Institution Press, Washington, DC. - Rappole, J. H., A. H. Kane, R. H. Flores, and A. R. Tipton. 1989. Seasonal variation in habitat use by great-tailed grackles in the lower Rio Grande Valley of Texas. Animal Damage Control Symposium, Ft. Collins, CO, U.S. Department of Agriculture. - Rappole, J. H. 2005. Evolution of old and new world migration systems: A response to Bell. Ardea 93:125– 131. - Rappole, J. H. 2013. The Avian Migrant: The Biology of Bird Migration. Columbia University Press - Recher, H. F., and J. T. Recher. 1969. Some aspects of the ecology of migrant shorebirds. 2. Aggression. Wilson Bulletin 81:140– 154. - Ricklefs, R. E. 1973. Ecology . Chiron Press, Newton, MA. - Rodrigues, M. 1996. Song activity in the Chiffchaff: territorial defence or mate guarding? Animal Behaviour 51, 709-716. - Rodríguez-Rodríguez, M. C. and Valido, A.2008. Opportunistic nectar feeding birds are effective pollinators of Bird-Flower from Canary Islands: Experimental evidence from Isoplexis canariensis (Scrophulariaceae). American Journal of Botany 95, 1408-1415. - Salewski , V., Bairlein, F., and Leisler, B. 2002.Different wintering strategies of two Palaearctic migrants in West Africa- a consequence of foraging strategies?. Ibis 144, 85- 93. - Scordato, E. S. C. 2017. Geographical variation in male territory defence strategies in an avian ring species. Animal Behaviour 126, 153-162. - Schubert G. 1971. .Experimentelle Untersuchungen über die artkennzeichnenden Parameter im Gesang des Zilpzalps (Phylloscopus c. collybita) (Vieillot). Behaviour 38, 289-314. - Sessions, P. H. B. 1966. Notes on the birds of Lengetia farm, Mau Narok. Journal of the East Africa Natural History Society. 26, 18-48 - Sharland, R. E. 1969. Ringing in Nigeria, 1968. Eleventh Annual report. Bulletin of the Nigerian Ornithological Society 6 : 26-29 - Simms, E. 1985. British Warblers. Collins. London - Simmons, K. L. 1954. Field notes on the behaviour of some Passerines migrating through Egypt. Ardea 42: 140-151. 40 - Sinclair, A. R. E. 1978. Factors affecting the food supply and breeding season of resident birds and movements of Palearactic migrants in a tropical African savanna. Ibis 120: 480- 497. - Sorensen, M. C. 2014. Singing in Africa: no evidence for a long supposed function of winter song in a migratory songbird. Behavioural Ecology 25, 909-915. - Stanford, J. K. 1954. A Survey of the Ornithology of Northern Libya. Ibis 96, 449-473. - Sæther, B. E. 1983. Habitat selection, foraging niches and horizontal spacing of Willow Warbler Phylloscopus torchilus and Chiffchaff Phylloscopus collybita in an area of sympatry. Ibis 125, 24-32. - Taylor, R. J. 1984. Predation. Chapman and Hall, New York. - Treherne, J.E, and Foster, W.A. 1981. Group transmission of predator avoidance in a marine insect: the Trafalgar effect. Animal Behaviour 29, 911-917. - Treuenfels, H. V. 1937. Beitrag zur Brutbiologie des Waldlaubsängers (Phylloscopus sibilatrix). Journal für Ornithologie 85, 605–623. - Trouche, L. 1946. Contribution a l'étude des oiseaux des Bouches-du-Rhône. I. Miramas. Alauda 14: 106–112 - Trune, D. R. and Slobodchikoff, C. N. 1976. Social effects of roosting on the metabolism of the pallid bat, Antrozous pallidus. Journal of mammalogy 57, 656-663. - Vafidis, J. O., Vaughan, I. P., Jones, T.H., Facey, R. J., Parry, R. and Thomas, R. J. 2014. Habitat use and body mass regulation among warblers in the Sahel region during the non- breeding season. PLoS ONE 9(11): e113665. https://doi.org/10.1371/journal.pone.0113665 - Wanink, J. H., and Goudswaard, K. 2002. The impact of Lake Victoria’s lakefly abundance on Palaearctic passerines. Ostrich 71, 194-197. - Weihs, D. 1973. Hydrodynamics of fish schooling. Nature 241, 290-291. - Witherby, H. F., Jourdain, F. C. R., Ticehurst, N. F. and Tucker, B. W. 1938. The Handbook of British Birds. Vol II. London. - Witmer, M. C., D. J. Mountjoy, and L. Elliot. 1997. Cedar Waxwing Bombycilla cedrorum . In The birds of North America (A. Poole, Ed.). Cornell Laboratory of Ornithology, Ithaca, NY. - Worton, B. J. (1989) Kernel methods for estimating the utilization distribution in home- range studies. Ecology 70: 164–168. - Worton, B. J. (1995) Using monte carlo simulation to evaluate kernel-based home range estimators. Journal of Wildlife Management 59: 794–800. 41 - Zwarts, L., Bijlsma, R. G, van der Kamp, J. and Wymenga, E. 2009. Living on the Edge: wetlands and birds in a changing Sahel. KNNV Publishing. Utrecht.

42 Appendix

Table 1 – bootstrap results for pairwise association among chiffchaffs.

# Pair Number of Mean distance Difference from Distance vs time gap paired obs. (m) bootstrap mean correlation (R2) 1 1X2 40 185 Not significant 0.0068 2 1X5 37 153 Not significant 0.005 3 1X9 21 237 Not significant 0.3506 4 1X10 20 211 Not significant 0.002 5 1X14 39 186 Not significant 0.1177 6 1X15 35 201 Not Signficant 0.0004 7 1X16 41 180 Not significant 0.0176 8 1X19 28 295 Not significant 0.0029 9 1X20 31 229 Not significant 0.0089 10 1X21 30 187 Not significant 0.1284 11 2X5 40 114 Not significant 0.0034 12 2X9 21 101 Not significant 0.0266 13 2X10 37 197 Not significant 0.0472 14 2X14 39 137 Not significant 0.0981 15 2X15 40 235 Not significant 0.0065 16 2X16 40 115 Not significant 0.1118 17 2X19 33 164 Not significant 0.0185 18 2X20 33 260 Not significant 0.0343 19 2X21 33 117 Not significant 0.0202 20 5X9 21 177 Not significant 0.16 21 5X10 33 198 Not significant 0.3595 22 5X14 40 145 Not significant 0.0458 23 5X15 42 238 Not significant 0.006 24 5X16 42 137 Not Significant 0.0166 25 5X19 33 220 Not significant 0.0007 26 5X20 32 229 Not significant 0.1053 27 5X21 34 131 Not significant 0.0092 28 9X10 18 170 Not Significant 0.6507 29 9X14 19 205 Not Significant 0.1631 43 30 9X15 19 279 Not Significant 0.0325 31 9X16 20 175 Not significant 7E-05 32 9X19 13 244 Not significant 0.0359 33 9X20 12 317 Not significant 0.0083 34 9X21 13 181 Not significant 0.0249 35 10X14 39 142 Not significant 0.0326 36 10X15 39 126 Not significant 0.1788 37 10X16 37 147 Not significant 0.0015 38 10X19 31 257 Not significant 0.081 39 10X20 34 91 Not significant 0.0177 40 10X21 33 148 Not significant 0.0554 41 14X15 39 108 Not signficant 0.0006 42 14X16 39 26 Not significant 0.1103 43 14X19 31 168 Not significant 0.0209 44 14X20 32 132 Not significant 0.0152 45 14X21 32 29 Not Significant 0.0012 46 15X16 38 126 Not Significant 0.0063 47 15X19 31 222 Not Significant 0.0042 48 15X20 30 77 Not Significant 0.0423 49 15X21 32 136 Not Significant 0.1452 50 16X19 33 158 Not Significant 0.0164 51 16X20 33 149 Not Significant 0.0646 52 16X21 32 21 Not Significant 0.0099 53 19X20 33 260 Not Significant 0.0282 54 19X21 34 169 Not significant 0.1245 55 20X21 30 150 Not Significant 0.0349

44 Table 2 – Kernel Density (KDE) home range areas and overlap percentage for tracked individuals of both species, using 90% and 50% of the relocations.

ID Species Start date End date Locations 90% KDE 90% total 50% KDE area 50% area (km2) overlap (km2) total (%) overlap (%) P01 P. collybita 16/01/2012 28/01/2012 37 0.120716 0.288848 0.037584 0.127419

P02 P. collybita 16/01/2012 28/01/2012 39 0.028414 0.338101 0.009831 0.198195

P05 P. collybita 16/01/2012 28/01/2012 36 0.117607 0.26143 0.031806 0.155853

P09 P. collybita 18/01/2012 22/01/2012 18 0.102726 0.237693 0.027648 0.174069

P10 P. collybita 18/01/2012 27/01/2012 32 0.11162 0.250905 0.03282 0.118736

P14 P. collybita 18/01/2012 27/01/2012 32 0.00237 0.6 0.000535 0.2

P15 P. collybita 18/01/2012 28/01/2012 31 0.018873 0.30019 0.003193 0.156667

P16 P. collybita 18/01/2012 28/01/2012 33 0.001495 0.546341 0.00044 0.233333

P19 P. collybita 20/01/2012 28/01/2012 27 0.016277 0.062555 0.004406 0

P20 P. collybita 20/01/2012 28/01/2012 27 0.017134 0.32327 0.003797 0.148113

P21 P. collybita 20/01/2012 28/01/2012 26 0.005254 0.455102 0.013943 0.162162

AVG: 0.049317 33% 0.013942773 15%

S03 S. cantillans 16/01/2012 28/01/2012 38 0.049306 0.059909 0.014782 0.022532

S13 S. cantillans 18/01/2012 28/01/2012 32 0.006082 0.272078 0.001332 0.25

S17 S. cantillans 18/01/2012 28/01/2012 14 0.024363 0.049607 0.00537 0

S18 S. cantillans 18/01/2012 28/01/2012 32 0.002942 0.438503 0.000624 0

S25 S. cantillans 23/01/2012 28/01/2012 17 0.000591 0 0.000153 0

AVG: 0.016657 16% 0.004452 5%

45

Table 3 – Minimum Convex Polygon home range areas for tracked individuals of both species using 95% and 50% of the relocations

ID Species Locations 95% MCP 50% MCP area area (km2) (km2) P01 P. collybita 37 0.030487 0.014828

P02 P. collybita 39 0.013151 0.004246

P05 P. collybita 36 0.061274 0.015083

P09 P. collybita 18 0.019234 0.001791

P10 P. collybita 32 0.031638 0.006447

P14 P. collybita 32 0.000739 0.000168

P15 P. collybita 31 0.007849 0.000066 P16 P. collybita 33 0.000434 0.000136 P19 P. collybita 27 0.006386 0.001555 P20 P. collybita 27 0.005122 0.000488

P21 P. collybita 26 0.000581 0.000131

AVG: 0.016081 0.004085 S03 S. cantillans 38 0.018864 0.008724 S13 S. cantillans 32 0.002891 0.000233 S17 S. cantillans 14 0.004008 0.000222 S18 S. cantillans 32 0.000817 7.75E-05 S25 S. cantillans 17 0.000173 0.00004 AVG: 0.0053504 0.001859

flick

20% PC True PC False 80%

Figure 1- percentage of Chiffchaffs exhibiting increased wing flicking in response to playback of conspecific song

46

Figure 2- Chiffchaff homeranges (KDE 90), their overlap pattern and the relocation points of all individuals.

Figure 3 – Subalpine Warbler homeranges (KDE 90), their overlap pattern and the relocation points of all individuals.

47

Figure 4- Chiffchaff homeranges (MCP 100), their overlap pattern and the relocation points of all individuals.

Figure 5- Chiffchaff homeranges (MCP 50), their overlap pattern and the relocation points of all individuals.

48

Figure 6—Subalpine Warblers homeranges (MCP 100), their overlap pattern and the relocation points of all individuals.

Figure 7-Subalpine Warblers homeranges (MCP 50), their overlap pattern and the relocation points of all individuals.

49