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Animal community structures, life histories and individual foraging behaviour are all an outcome of a trade-off between competition for resources (and thus the risk of starvation) and survival (and thus the risk of predation). The relative importance of these factors however, differs between ecosystems, and especially when comparing temperate to tropical ones, we usually find marked differences. The seasonality of tropical ecosystems is much reduced compared to temperate ones, and weather conditions are less extreme. Accordingly tropical systems are characterised by higher species diversity, and different life history traits have been found between temperate and tropical birds. However, how the different environmental factors interact, and how predation and starvation risk vary to cause these differences still remains largely unknown. We studied the feeding behaviour of several granivorous Estrildid finches in scrub savannah habitat in central Nigeria to test how they respond to varying degrees of starvation and predation risk. During field observations and aviary experiments we investigated whether there is seasonal variation in the birds’ foraging behaviour correlating with the abundance of grass seeds and tested how they respond to different group sizes and differing distances from cover (representing a difference in predation risk). Further we also carried out field observation on the natural feeding behaviour of several closely related sympartic Estrildid finches to investigate inter-specific and seasonal differences in competition and microhabitat choice to see if this could explain their coexistence. Finally we studied habitat choice, movement behaviour and breeding biology of the potentially threatened endemic Rock Firefinch (Lagonosticta sanguinodorsalis) between the wet and the dry season via radio-tracking to establish its habitat requirements and gain the first information in its life history traits and population trends. We found little seasonal variation in the species’ foraging behaviour, and parameters that varied did not do so in a consistent manner. Thus, we found little evidence for a seasonal change in the risk of starvation. However, the abundance of several bird species varied widely between seasons and species leaving during periods of food shortage might have released competition for remaining resources. Birds did not show a strong response in their feeding behaviour with respect to cover in either intake rate or timing of feeding. However, intake rate increased with group size, which we believe to be due to scramble competition rather than risk dilution. We therefore conclude that predation did not shape the foraging behaviour of tropical granivorous passerines as markedly as that of temperate ones. Rock Firefinches were found to breed between the late rainy and the early dry season. They selected inselberg habitat, where most nests were found between rocky boulders. During the dry season, when water sources in inselberg habitat had dried out, they had to fly distances of up to 700 m to the gallery forest to get water and this led to the inclusion of more scrub savannah and gallery forest within their home ranges. Daily egg survival was 0.89 ± 0.03 calculated after the Mayfield analysis and most failing nests were depredated probably mainly by lizards. We suggest that in addition to nest predation, water availability might limit breeding time and thus reproductive output of Rock Firefinches. Predation risk did not seem to be of high importance in shaping the birds’ feeding behaviour because there was no seasonal variation in the risk of starvation. We found some suggestive evidence that competition might be important and it is likely that bird populations constantly stay close to carrying capacity. In contrast to temperate regions the need to conserve water might be of higher importance in shaping the birds’ feeding behaviour. High adult survival rates might be due to reduced seasonality in the risk of starvation thereby leading to reduced predation risk on adult birds. High nest predation might also be of higher importance in shaping the life history traits of tropical passerines, but at present this suggestion remains speculative. The results fit into the general framework that there is a trade-off between starvation and predation risk, and in the absence of starvation risk for some species in tropical areas, predation risk is also relatively unimportant.

Strategic allocation decisions, in particular trade-offs between reproductive and somatic investment, are central to life history theory. The allocation of resources to body mass maintenance is beneficial for avoiding starvation, but is costly because resources are diverted away from the current reproductive effort, and mass-dependent costs are increased. Stochastic dynamic models have been developed to investigate optimal routines of mass regulation and behaviour in male birds displaying to attract a mate. What is central to these models, and to any empirical investigation of the trade-off, is the dynamic interaction of body mass regulation and display behaviour routines. Previous experimental work has focussed on each of these factors in isolation, but never in unison. This work addressed this shortfall by examining the dynamic interaction of investment in reproduction versus somatic investment in male zebra finches (Taeniopvgia guttata), a theme discussed more fully in chapter 1. Chapter 2 provides details of software and hardware that I created in order to enable body mass and display hopping activity of males to be automatically recorded. Further, it describes software and hardware that controlled the lighting and temperature of the experimental environment and finally it discusses software I created to perform post-hoc processing of the data which were generated. The lighting controller sought to mimic the variations in light intensity associated with twilight. In chapter 3, I describe an experiment which tested the effect of naturalistic light intensity control versus 'all- or-nothing' lighting on the mass regulation and display behaviour of male zebra finches. In the experiment described in chapter 4, I presented male zebra finches with four stimulus treatments which inherently varied in their potential to be courted, and I recorded diel patterns of body mass regulation and hopping activity. The stimulus cage contained either: no stimulus bird, a female bengalese finch, a male zebra finch, or a female zebra finch. There were significant effects of treatment on mean body masses and display hopping activity, with lowest mean masses and highest display activity during the female zebra finch treatment. Mass trajectories did not differ between treatments, instead the effect of treatment was manifested as a complete shifting in the y-axis of the mass curves. Hopping activity trajectories did however vary between treatments with the female zebra finch stimulus evoking a marked peak around dawn. This apparent anomaly may be attributed to either strategic compensatory foraging aimed at guarding mass trajectory, variation in the mass-dependent costs of display behaviour, a reorganisation of time and energy budgets, or some combination of these factors. This work provided the first experimental evidence of the trade-off between reproductive and somatic investment in birds. The diel patterns of display activity exhibited by many male passerines could be due to temporal variation in either male-state or in female-state (i.e. her attractiveness and/or receptivity). These effects are naturally confounded, but by desynchronising the photoperiods of the female stimulus birds from the males it was possible to disentangle the effects of the time of presentation and time-state of the female on male mass regulation and display activity. Female zebra finches were presented to the males for a discrete three hour period at dawn or midday, and in each case females were either in a dawn or a midday time-state (making four treatments in total). The time of presentation had no effect on overall display rates, but the peaks of display activity were shifted to coincide with the time when the female was present. Despite no difference in mean hopping activity, there was a significant effect of presentation time on mean mass, which I attributed to time of day differences, due to male-state, in the costs of display. Female time-state was for the first time shown to influence display activity of males. Dawn-state females were more attractive/responsive and evoked a greater display effort, but only in the context of the males' dawn, as no effects of female time-state were apparent at midday. Arbitrary symmetry has been shown to influence female choice in birds, particularly in zebra finches. We investigated the effects of arbitrary symmetrical and asymmetrical traits of females (applied as coloured leg bands) on the dynamic interaction between body mass regulation and display activity in male zebra finches (chapter 6). We found no significant effects of leg band treatment on either overall levels of body mass and display hopping, or on their diel trajectories, all of which were highly consistent between treatments. There was however a significant and consistent effect of female identity (irrespective of leg banding) on male display hopping activity. This fact, coupled with evidence from chapters 4 & 5 that the trade-off exists and can be detected by the present experimental design, points towards arbitrary symmetrical traits of female zebra finches having no effect (or a very weak effect) on male choice, unlike the situation that occurs when the sex roles are reversed.

Chapter 1 provides an introduction to the thesis by discussing the relevant literature on vocal learning in songbirds and parrots, with particular reference to calls, and setting out the aims of the following chapters. Chapter 2 concerned an investigation of the similarity in the distance calls within and between families of zebra finches, involving fostering young birds to non-related parents. Male offspring were most similar in their distance calls to their male siblings with which they were raised and the adult male which raised them, suggesting an environmental influence in the acquisition of the call. There was also an indication that the call may be, at least in part, inherited. Females were most similar to their mothers and female siblings, though not to the same extent as in males. Chapter 3 examined whether male zebra finches could exhibit vocal plasticity in adulthood, by learning new calls from other conspecifics, and whether social deprivation during a young bird's development would accentuate this tendency. Adult zebra finches could not learn new calls from other similarly raised cagemates, even if these birds were reared under conditions of extreme social deprivation and were presented with an appropriate normally-raised adult male tutor. Chapter 4 described a study which investigated whether adult male budgerigars housed in soundproof boxes, could learn new calls from a tape recording in the absence of any social stimuli. Learning from tapes was very limited with only one bird producing an accurate copy of the playback, emphasising the importance of an interactive social context in vocal learning. Chapter 5 attempted to determine exactly which social factors were most influential in determining the extent of call matching between adult male budgerigars. Certain individuals did match more closely in their contact calls; close proximity appeared to promote call convergence between cagemates. Chapter 6 examined the effect of adding an unfamiliar budgerigar to an established flock, on the group specific call. It was found that, contrary to expectation, mutual imitation by all flock mates did not occur as other studies have shown, and that 'new recruits' conformed to the shared group call. Chapter 7 concluded the findings of the five experimental chapters, and discussed their significance with reference to previous studies, including ideas for further investigation.

Bird song provides us with one of the best models with which to investigate learning, communication and the organisation of behavioural repertoires. This study describes temporal organisation and song pattern choice in the chaffinch in order to develop hypotheses for possible song control mechanisms. Influences of the song learning process and motivation on performance are tested in experiments. The role of nature and nurture in shaping females' song preferences is investigated by using operant tasks. A first quantitative assessment of temporal organisation within songs is provided in Chapter 2. Chaffinches sing with eventual variety, each song type in a male's repertoire is repeated a few times before a switch to the next type occurs. Chapter 3 tests two hypotheses for mechanisms controlling song type switching: that a maximum number of repetitions or that a maximum duration (time window) sets the upper limit. Clear evidence for a time window as an upper constraint was found in wild birds as song type bouts with many repetitions were sung at fast rates only, whereas those with few repetitions could be sung at either fast or slow rates. However, the mean number of song type repetitions depended strongly both on the subject and the song type. No evidence could be found that number of repetitions per song type were influenced by the tutor's singing style in hand-reared chaffinches (Chapter 4). Playbacks of single songs to wild males revealed the motivation dependent flexibility of the system as the birds reacted with distinct increases in bout duration (Chapter 5) but showed a different response to playbacks of songs that were the same or different from that being performed by the subject. Song was used as a positive reinforcer in an operant conditioning task with female chaffinches (Chapter 6). The influence of early exposure to song on later preferences and the relative importance of the trill and flourish sections of the song were tested this way. Females showed no preference for familiar over unfamiliar songs, but preferred songs with flourishes over those without.

The acoustic adaptation hypothesis was reviewed. This predicts that the sounds used by birds singing in a dense habitat should be of lower frequency than those in a more open habitat, and that sounds should be spaced out more in time in denser habitats to avoid degradation by reverberations. These predictions were tested by recording chaffinch (Fringilla coelebs) songs in open scrub, coniferous plantations, and a natural Scots pine forest, but the results obtained gave little support to the predictions made. Transmission of white noise and the songs of blue (F. teydea) arid Canary Islands chaffinches (F. c. tintillon) through laurel and Canarian pine forests on Tenerife revealed a sound window of less excess attenuation than expected in both habitats at frequencies of 2-3kHz. The song of the blue chaffinch appears to be better adapted for transmission through both habitats. Computer simulations of the formation of dialects by random copying of the songs possessed by neighbours predicted a strong effect of both the number of neighbours available to learn from, and the repertoire size, upon the songs' longevity and the number of birds sharing a particular song type. If the song type which was commonest amongst those sung by neighbours was learnt, larger groups of birds were found to share song types. At low copying error rates these groups approached the size of those described for the white-crowned sparrow (Zonotrichia leucophrys). A computer program which uses the dynamic programming algorithm to compare objectively shapes digitised from sonagrams was developed and tested with syllables from chaffinch songs.

Using a laboratory approach, this thesis further' investigates patterns of song learning in the zebra finch (Taeniopygia guttata). Chapter 1 provides a background to the form and function of song learning in a broad context, and introduces the zebra finch and the major role it has played in this field of research. In Chapters 2 and 3, a strong influence of early visual imprinting on song tutor choice is demonstrated. Tutors of the same colour morph as the parents were much preferred. Song heard before or after the sensitive phase was often produced, if no tutor of the parental morph was present during this period. There was no clear evidence for one parent having a greater influence in this respect than the other. Differences were found between the morph preference for mates and song tutors, and possible reasons for these are discussed. Chapter 4 revealed that the mother may influence tutor choice, probably by attentiveness to her by her offspring increasing their exposure to the song of an accompanying male. There was also a preference for a paired, rather than a single, male. In Chapter 5, song tutor choice was studied in aviaries and related to behaviour occurring in this more naturalistic environment. A preference for learning the father's song was found). Specific types of interaction did not link overall with song copying, but the amount of time that birds spent within close proximity did. General aspects of behaviour evident in the aviaries are discussed. The final chapter demonstrated that a short distance (38 cm) between tutor and tutee can be sufficient to inhibit song learning, probably because of the reduced scope for interaction.

This thesis examines the importance of visual, vocal and behavioural cues for song tutor choice in zebra finches, Taeniopygia guttata. Zebra finch males normally copy song at 35 to 65 days of age. In the wild the young become independent at about 35 days of age and form small flocks in the area of the colony where they will be exposed to a variety of song tutors. In Chapter 3 captive zebra finches are provided with the opportunity to learn from two conspecifics at 35 days of age. Female-raised males which are housed with two unrelated tutors prefer to learn from the one who is, most aggressive towards them. Normally-raised males which are housed with an unrelated tutor and one, whose song is similar to the father's tend to copy the tutor with the similar song: this relies on the young bird learning some characteristics of his father's song before independence. Chapter 4 shows that males and females can discriminate between their father's song and those of other males. Visual, vocal and behavioural cues are all important for species-specificity. Cross-fostering using Bengalese finches, Lonchura striata, as foster-parents is an important tool for studying this. Chapter 5 looks at Bengalese finch song development; Chapter 6 compares song development in cross-fostered zebra finches and Bengalese finches. Visual cues are important for tutor choice and young males of both species which are provided with a zebra finch singing Bengalese song and a Bengalese finch singing zebra finch song prefer the conspecific tutor (Chapter 7). Chapter 8 suggests that conspecific song elements are not important for zebra finches: there is no tendency to prefer a tutor with normal song over one singing Bengalese song. Cross-fostering can also, influence the timing of song learning. Males which are housed successively (Chapter 9) or simultaneously (Chapter 10) with both species tend to reproduce song which they heard before independence in addition to learning from the tutor which they heard after independence at 35 to 65 days of age: this indicates that the timing of the sensitive phase is flexible and mediated by both experience and age. There are a number of similarities between song learning and sexual imprinting which are discussed in Chapter 11. Crucial to these studies is a knowledge of the two species' behaviours. Chapter 12 compares, parental behaviour in captivity. Chapter 12 concludes with a plea for more research in the wild.

Several studies have looked at the importance of man-made water resources to wildlife in desert regions. To our knowledge, however, none have attempted to directly quantify their importance to both resident and Neotropical migratory birds. During the spring and summer from 2007-2009, we enriched man-made water developments in the Sonoran Desert on the Kofa National Wildlife Refuge, Arizona. We enriched water developments using deuteriated water and sampled the body water pools of resident and migrant birds to quantify development use. We used a simple two end-point mixing model to estimate the proportion of an individual birds body water pool that was derived from the development water. We mist netted birds at distances ranging from 2 to 1000 m from the development to assess the distance an individual would travel to use these permanent water sources. We analyzed samples from 1,431 birds and found that resident species (253 out of 394 individuals sampled) such as Gambel's Quail (Callipepla gambelii), White-winged Doves (Zenaida asiatica), Mourning Doves (Zenaida macroura), and House Finches (Carpodacus mexicanus) made extensive use of the water developments. Water developments contributed as much as 90% of the water found in the body water pools of some species (e.g. White-winged Doves, Mourning Doves and House Finches). Other species such as Northern Mockingbirds (Mimus polyglottos), Gila Woodpeckers (Melanerpes uropygialis), and Phainopeplas (Phainopepla nitens) made limited use (29 out of 91 individuals sampled) of these developments during the summer months. In contrast, very few Neotropical migrants (9 out of 364 individuals sampled) used these developments during their northward migration in the spring. For small, resident species, such as Verdin (Auriparus flaviceps), Black-tailed Gnatcatcher (Polioptila melanura), Lucy's Warbler (Vermivora luciae), and Black-throated Sparrow (Amphispiza bilineata), these permanent water sources appear to be of limited importance to their daily water balance.

In this four-part study, I use selection analyses to examine the evolutionary significance of morphological, behavioral, and life history variation in a population of Darwin's Medium Ground Finches (Geospiza fortis). The first section describes the natural selection on adult body size in G. fortis that occurred following the extremely wet conditions present during the El Nino event of 1983. High adult mortality was correlated with directional selection for small body size. This contrasts with the strong directional selection for large size observed following droughts, and implies that selection on body size in these birds may fluctuate regularly. In the second part, I focus on the heritability of and selection on clutch size in these birds. Quantitative genetic analyses indicate that, in contrast to all other species so far, there is no evidence for heritable variation in clutch size among females. Selection analyses suggest this may be due to a history of sustained directional selection favouring large clutches in this population. In part three, I use a pedigree analysis to estimate levels of inbreeding in the G. fortis population. Levels of inbreeding are comparable to those observed in other passerine species. Degree of pair-relatedness did not have any effect on the reproductive success of individuals and simulation analysis indicate that mate choice in these birds occurs at randomly with respect to relatedness. Kin avoidance does not appear to be an important determinant of levels of inbreeding in this population. Finally, in the last section, I examine the patterns and causes of changes in the frequency of different male song types. Over a six-year period the song type that was most common became significantly rarer while the other three less common song types all increased in frequency. This pattern of frequency-dependent change occurred because males with uncommon songs survived better and produced more offspring. Thus, song type variation appears to be adaptive in this population and biological and cultural evolution are more closely coupled processes in these birds than in other species.

Abstract: Masters thesis. Breeding redpolls in Inuvik and Krekovick Landing, NWT were observed during the summers of 1977 and 1978.