The object of this study was to determine the normal thermoregulatory patterns of zebra finches (Poephilia guttat) in as near a normal physiological and behavioral state as possible. Surface body temperature and level of activity were the two primary channels of information. Radiobioelemetry allowed the reduction of external disturbance during long periods of continuous recording.

Over the past twenty years there has been an exponential increase in the investigation of maternal effects. Understanding the adaptive function of maternal allocation strategies is integral to interpreting the evolutionary outcomes of sexual selection. Thus, model animal systems that facilitate experimental manipulation and controlled investigation of the physiological and behavioural mechanisms underlying maternal effects are important to evolutionary biologists. The zebra finch (Taeniopygia guttata) has been used as a model to investigate avian life-history, signalling behaviour, neurophysiology, mate choice, and more recently, maternal effects. However, a potentially influential and rarely addressed problem with this species is the process of domestication. Within this thesis we aimed to both test current predominant maternal allocation hypotheses, but for the first time in both domesticated and wild zebra finches. Chapter 2 develops on earlier work using domesticated zebra finches that has demonstrated differential allocation of maternally derived yolk androgens and antioxidants in eggs dependent on paternal attractiveness. This chapter specifically tests the ratio of these two yolk resources within individual eggs and shows that the balance of androgens to antioxidants varies by offspring sex and paternal attractiveness. Specifically, we found that mothers allocated a smaller androgen to antioxidant ratio to daughters when paired to green ringed (unattractive) males compared to red ringed (attractive) males. This pattern was reversed for sons, where mothers allocated a larger ratio of androgen to antioxidant when paired to red ringed (attractive) compared to green ringed (unattractive) males. We also show that brood sex ratio depended on both female condition and male attractiveness. It is concluded that investigating female allocation of individual resources within egg yolks may lead to incorrect assumptions on offspring fitness consequences, and that individual female state is an important consideration when predicting a resource allocation strategy. Throughout this thesis colour bands are used as a method to manipulate male attractiveness. In chapter 3 the influence of these bands was further tested to elucidate whether they affect male behaviour or quality. Wild birds were used for this chapter as preferences for bands based on colour have only once been demonstrated in wild birds and it was felt this should also be replicated. We confirmed a female preference for males based on colour bands worn in mate choice trials, with red bands preferred over green. Interestingly, we also found that colour of bands worn by males for an extended period in the single sex aviary influenced both their song rate and condition. Males that had worn red bands sang more in mate choice trials than both green banded or un-banded males. In addition red banded males were found to be in significantly better physical condition. These data suggest that earlier experiments in which it has been assumed that colour bands do not manipulate any form of intrinsic male quality should be re-evaluated. The final two data chapters, 4 and 5, return to investigating maternal allocation in response to male attractiveness, but for the first time in wild birds. Chapter 4 presents an experiment that was conducted on a wild, nest box breeding population of birds. Maternal resources allocation was investigated in both an experimental manipulation of male attractiveness, and also by correlating resource allocation with paternal phenotypic traits. A limited sample size meant few conclusions could be drawn from the experimental study, but significant positive correlations were found between both egg size and yolk testosterone (T) concentration and male phenotypic traits. This suggested that wild zebra finches may follow a positive investment strategy but requires further investigation. In chapter 5 experiments were repeated on wild birds that had been brought into captivity, to allow both an improved sample size and further control of influential environmental features. Again, female allocation strategies are tested using colour bands to manipulate male attractiveness, to allow direct comparisons with work on domesticated zebra finches. We found that females laid significantly heavier eggs for attractive compared to unattractive males, supporting the positive investment hypothesis. In addition we found an interaction between offspring size and paternal attractiveness treatment, with daughters of red banded (attractive) males being smaller than sons. This experiment is the first to demonstrate the influence of colour bands on maternal allocation in wild zebra finches and also provides further support for the positive investment hypothesis in this species. The final chapter discusses how overall patterns of female allocation were shown to be similar among wild and domesticated populations. It is concluded that demonstrated variations between populations and/or contexts reported in these studies cannot be explained by inherent differences between wild and domesticated individuals. Thus, the zebra finch remains a robust and reliable model for testing the evolution of avian maternal allocation strategies.

I am interested in discovering the role of field potential oscillations in producing synchrony within the song system of the male zebra finch brain. An important function attributed to neural synchrony is sensorimotor integration. In the production of birdsong, sensorimotor integration is crucial, as auditory feedback is necessary for the maintenance of the song. A cortical-thalamic-cortical feedback loop is thought to play a role in the integration of auditory and motor information for the purpose of producing song. Synchronous activity has been observed between at least two nuclei in this feedback loop, MMAN and HVC. Since low frequency field potential oscillations have been shown to play a role in the synchronization of nuclei within the brain of other model animals, I hypothesized that this may be the case in the zebra finch song system. In order to investigate whether oscillatory activity is a mechanism behind the synchronous activity observed between HVC and MMAN, I performed dual extracellular recordings of neural activity within the zebra finch song system. Results suggest that oscillations are likely not involved in the synchrony observed in these nuclei. Future study may reveal that the structure of the feedback loop is necessary, and possibly even sufficient, for the synchronous activity in the zebra finch song system.

The Australian Zebra Finch (Taeniopygia guttata) is an important animal model for vertebrate development and behavior. New research initiatives in the fields of epigenetics rely heavily on injecting hormones and environmental toxins directly into the eggs of different bird species such as zebra finches and other passerine songbirds to replicate the effects maternal condition on offspring. However, the widely used method of egg-injections does not accurately replicate physiological conditions, as the injected substances remain concentrated at the injection site for extended periods and do not diffuse into the developing tissues. Therefore, we propose an alternative method to injection protocols that takes advantage of the porous nature of eggs. Corticosterone (CORT), a major vertebrate stress hormone, dissolved in ethyl alcohol was applied to the surface of zebra finch eggs daily. The effect of this treatment on decreasing hatching success shows that topical hormonal treatments are a viable alternative to egg injection.

Sequences of stereotyped actions are central to the everyday lives of humans and animals, from the kingfisher's dive to the performance of a piano concerto. Lashley asked how neural circuits managed this feat nearly 6 decades ago, and to this day it remains a fundamental question in neuroscience. Toward answering this question, vocal performance in the songbird was used as a model to study the performance of learned, stereotyped motor sequences. The first component of this work considers the song motor cortical zone HVC in the zebra finch, an area that sends precise timing signals to both the descending motor pathway, responsible for stereotyped vocal performance in the adult, and the basal ganglia, which is responsible for both motor variability and song learning. Despite intense interest in HVC, previous research has exclusively focused on describing the activity of small numbers of neurons recorded serially as the bird sings. To better understand HVC network dynamics, both single units and local field potentials were sampled across multiple electrodes simultaneously in awake behaving zebra finches. The local field potential and spiking data reveal a stereotyped spatio-temporal pattern of inhibition operating on a 30 ms time-scale that coordinates the neural sequences in principal cells underlying song. The second component addresses the resilience of the song circuit through cutting the motor cortical zone HVC in half along one axis. Despite this large-scale perturbation, the finch quickly recovers and sings a near-perfect song within a single day. These first two studies suggest that HVC is functionally organized to robustly generate neural dynamics that enable vocal performance. The final component concerns a statistical study of the complex, flexible songs of the domesticated canary. This study revealed that canary song is characterized by specific long-range correlations up to 7 seconds long-a time-scale more typical of human music than animal vocalizations. Thus, the neural sequences underlying birdsong must be capable of generating more structure and complexity than previously thought.

<p>The development of the avian embryo is dependent of heat provisioning from the parents. To increase the heat transfer to a cooled egg the Zebra finch females develop a brood patch. Mild cooling generally constricts the blood vessels but the Arterio-venous anastomoses (AVA) in the brood patch in birds dilate. This is called cold-induced vasodilation CIVD. The Zebra finches were anesthetized with isoflurane and the brood patch was stimulated with a cooling probe set at 20-21 °C. Differences in the vascular changes to cooling in broody and non- broody birds were studied by comparing males and broody females. The brood patch skin was cooled, but no cold-induced vasodilation (CIVD) was documented for the males or the broody females. Isoflurane anesthesia depresses the sympathetic nervous system activity and the results support that the mechanism for CIVD in the brood patch of Zebra finches depends on a neural pathway, but does not exclude a local non-neural mechanism.</p>

<p>During the breeding season Zebra finch, Taeniopygia guttata, females develops a brood patch on the ventral surface which facilitates heat exchange between the incubating bird and the egg. The brood patch has to be sensitive to changes in temperature, so that the eggs can be kept at an optimal temperature for embryo development. If the egg temperature drops it has to be re-warmed. Mild cooling of the brood patch has been shown to cause cold induced vasodilation, but the responsible mechanism for this is not known. In this study we investigated if known thermoreceptors, TRPV3 and TRPV4, could be involved in the alteration of blood flow. To activate TRPV3 and TRPV4 two agonists, carvacrol and 4α-PDD respectively, were applied on the brood patch. Changes in skin temperature and vascularity were then examined. The results obtained did not reveal any changes in the vascularity. Temperature changes in the skin that could be caused by an alteration in blood flow did not significantly change either. Still, a role of these channels in the brood patch cannot be excluded.</p>

During the breeding season Zebra finch, Taeniopygia guttata, females develops a brood patch on the ventral surface which facilitates heat exchange between the incubating bird and the egg. The brood patch has to be sensitive to changes in temperature, so that the eggs can be kept at an optimal temperature for embryo development. If the egg temperature drops it has to be re-warmed. Mild cooling of the brood patch has been shown to cause cold induced vasodilation, but the responsible mechanism for this is not known. In this study we investigated if known thermoreceptors, TRPV3 and TRPV4, could be involved in the alteration of blood flow. To activate TRPV3 and TRPV4 two agonists, carvacrol and 4α-PDD respectively, were applied on the brood patch. Changes in skin temperature and vascularity were then examined. The results obtained did not reveal any changes in the vascularity. Temperature changes in the skin that could be caused by an alteration in blood flow did not significantly change either. Still, a role of these channels in the brood patch cannot be excluded.

It is well established in mammals that chronic, long-term elevations in sex steroids are associated with improvements in spatial cognition. It is less clear the extent to which short to medium term elevations in sex steroids improve spatial cognition and change hippocampal morphology, particularly in birds. The avian hippocampus expresses both androgen receptors (AR) and oestrogen receptor alpha (ERα) and high levels of the enzyme aromatase that converts testosterone to oestrogen. I began by comparing spatial cognition, hippocampal sex steroid receptor and aromatase expression between males and females. There were no differences in spatial or visual cognition or in hippocampal sex steroid receptor expression between the sexes, although hippocampal aromatase mRNA expression was higher in males. I then addressed the effects of acute and medium-term sex steroid treatment on spatial cognition and hippocampal aromatase and sex steroid receptor expression. A single treatment of testosterone 30 minutes or four hours prior to cognitive testing improved spatial performance. Additionally, when testosterone and oestrogen were given daily for five days spatial cognition in both sexes was improved. The testosterone-induced improvement was blocked when testosterone was administered in conjunction with the aromatase inhibitor fadrozole but not when administered with saline. These findings suggest that spatial cognition is improved by an oestrogenic effect. Thirty minutes following acute testosterone treatment, plasma testosterone levels, hippocampal AR and ERα mRNA expression all increased. Five days of oestrogen treatment increased plasma oestrogen levels, hippocampal ERα mRNA and Nmethyl- D-aspartate (NMDA) receptor levels in males and females; all were positively correlated with enhanced spatial cognition on day five of treatment. Finally, I determined which genes were differentially expressed as a result of five days of oestrogen treatment. Nineteen genes, identified as being involved in learning and memory were differentially expressed in the hippocampus, eleven of which were up-regulated and eight were down-regulated. Taken together these results demonstrate that oestrogen can improve spatial cognition in birds. It is plausible that oestrogen acts to improve spatial memory in the hippocampus through upregulation of genes that control neurotransmitter release, reuptake and receptor levels.

In the zebra finch (Taeniopygia guttata), song and its social context play an important role in female mate selection. The song of the zebra finch is unique in that it can only be produced by males, which makes the species ideal for analyzing the components of male song that influence female song preference and mate selection. There are three consistent features of zebra finch song that affect female mate preference: 1) the amount of time a male sings, 2) the size and complexity of his song repertoire, and 3) the structural conformation to species or population norms (reviewed in Nowicki et al. 2002). During courtship, male zebra finches often express ‘static-visual’ and ‘dynamic-visual’ elements in sync with song (Morris 1954), which would suggest that such behaviors also play a role in influencing female mate preference. However, with courtship comes the competition between males for the attention of potential mates. These agonistic interactions between males act settle disputes over access to mates, and as such, are also likely to influence female mate selection. As follows, we predict that, at the initial onset of courtship, there would be a higher prevalence of male-to-female courting interactions and singing behavior in comparison to male-to-male agonistic tendencies if female mate selection is fundamentally determined by song preference. However if female mate selection is more complicated than simple song preference, we would expect to initially observe a higher number of agonistic interactions between males as they compete for dominance. This hypothesis was tested by recording and analyzing the behavioral interactions between male and female zebra finches in the context of song complexity. We found that different males scored higher for song complexity than those for expression of courtship behaviors, which indicates that different elements of male courtship display likely influence female mate preference. Our data comparing male-to-male interactions and male-to-female interactions within the first 30 minutes after introduction was statistically insignificant, suggesting that female mate selection is more complicated than simple song preference. This preliminary research can be used as a basis for future studies using quantitative movement tracking analysis, which would further strengthen these initial observations. By increasing our understanding of the influence the male song has on female mate selection, we can better expound upon the nature and function of the favored traits that male songbirds possess and the benefits that females and their progeny might gain from choosing a male with these particular attributes.