Australian Zebra Finch Research Articles

Crowded House (Don't Dream It's Over), and: Remembering Our Birds

Crowded House (Don't Dream It's Over), and: Remembering Our Birds Safia Jama (bio) Crowded House (Don't Dream It's Over) Nonsensical beauty. All the plateshe broke on accident rememberhappier days. Honey, it's overbut let's still dream of the early days. That first Christmas in Ireland.That was something. Tinsel walls,hors d'oeuvres I would somedaymake at parties our friends would come to miss. Reminiscentof 1966. My parents' dream kitchen.Pots and pans float and fade. Moreplates explode. One, you broke on purpose, and I now whisper intothe drummer's ear: "Cameras arerolling. Smile." Near the end,Darrell filmed in our living room. Still together, still hanging on,though oatmeal stood hardeningon the stove. Future rocks we'dthrow at one another. 1986 was a good year, maybe the lastgood year for some time. Nowthe lead singer is vacuumingand soon the bassist will play [End Page 137] an organ solo wearing his matadorjacket. Mix and match like thrift storesand flea markets and you and me.Crowded House has not forgotten a single detail, poring over photoalbums. A candelabra lights a corner.I watched this video every night for days—then weeks, until, at last, I walked across greengrass did greet me. Remembering Our Birds I watch sunrise on square windowsthat remind me of those reflective aviator glassespeople sometimes wear— I bought a pair that first spring you visited me,and I wore them without irony,just as I used to wear everything. I left my wardrobe at our old apartmentyou kept like a museum, not moving a singlepillow for a year. Your main design contribution, two Australian zebra finches, purchased that April,our first big rumble. I left, and you replaced my absencewith caged birds. When I returned in the fall, I learned to accept our new pets, the vestige of my leaving, the symbolof our ongoing troubles. When we fought, the birds fought. When we loved, the birds preened and on the afternoonI packed to go to my mother's, you picked a newly [End Page 138] hatched chick off the kitchen floor and placed itin the palm of my hand. You have to keep it warm or it will die!My heart had fled the coup, I didn't care,only I didn't want that warmth to leave,and we named the chick Baby. I went to my mother's for a week, and Baby grew bigger,and the parents raised Baby until she became full grownand belligerent. I had no idea what it meant to save a lifethat would eventually turn around and attack,but then again, I'm not a parent. This morning, I watched the sun rise across the windowswhere I have been nesting here these nine days. Olive, the finch that I chose from the pet store, died last year.You said when you looked into her eyes, she looked backand called in tears when Olive was ill. You took that $15bird to the vet and spent $400. She didn't make it,but I was glad you tried, and so were you. That's when you found Emily, the small white birdmeant to replace Olive. Pip never took to Emily, though,so you kept her in a studio apartment nearby and you told meshe enjoys her solitude and spends her timecontemplating poetry. Last Thanksgiving, our second year apart,you were out all night, and when you came home,Emily had drowned herself in the fish tank,her white feathers bobbing among the Amazon weeds,Sir Claude, your prized fish, looking on perplexed. I said it was a very literary death, and felt disturbed and sorryand fascinated. We were out walking in the snow and youwere trying hard to be kind. [End Page 139] I felt something new,something akin to the frozen snow—the winter sun burning the bare treestouched a pain I needed to feel, to knowthat I am still here and alive. Those first birds, the vestiges of our...

Experimentally reduced feather microbial loads improve reproductive performance in captive Zebra Finches

AbstractWe performed a laboratory experiment on caged, domesticated Australian Zebra Finches (Taeniopygia guttata castanotis) to assess the effects of antimicrobial treatment applied to birds’ plumage on the feather microbial loads of breeding pairs and their associated reproductive performance. Treatments included an experimental group that experienced frequent misting with a broad-spectrum antimicrobial, as well as 2 control groups. Microbial loads (colony forming units [CFUs]) sampled from the belly feathers of breeders were higher posthatching than prehatching, and experimental pairs had lower loads (one-half to one-third the CFU counts) than controls at all sampled breeding-cycle stages. Clutch size and hatching success did not differ among treatments, but experimental pairs fledged nearly 50% more offspring (mean = 3.5 per clutch) than controls (mean = 2.3 per clutch) due to experiencing much lower nestling mortality. Offspring development rate, as assessed by one metric, varied among treatments: beak color score sampled midway in the development of adult phenotype revealed that offspring of experimental pairs had more rapid development. Findings imply that experimentally reduced density of feather microbial loads on breeders decreased reproductive costs in the posthatch phase, resulting in increased offspring survival and condition. At the time offspring fledged, uropygial gland volume tended to be greater among breeders that had experienced antimicrobial application throughout the breeding cycle. These results are consistent with a growing literature showing that the feather microbiome contributes significantly to the evolution of avian life histories and behavior and indicate that Zebra Finches are a useful laboratory model for investigating in vivo effects of the feather microbiome on avian hosts.

Relative Water Economy Is a Useful Index of Aridity Tolerance for Australian Poephiline Finches

We evaluate if the iconic Australian Zebra Finch (Taeniopygia guttata) has a unique physiology or if its metabolic, thermal and hygric physiology are similar to other Australian poephiline finches, by comparing it with three other species, the arid-habitat Painted Finch (Emblema pictum) and the mesic-habitat Double-barred (Taeniopygia bichenovii) and Red-browed (Neochmia temporalis) Finches. All physiological variables responded to ambient temperature as expected. There were no species differences for any of the standard physiological variables, consistent with the hypotheses that birds are pre-adapted to arid habitats, the recent development of Australian deserts has limited opportunity for physiological adaptation, and all four species share similar behavioural and ecological traits. Nevertheless, the ambient temperature where metabolic water production equals evaporative water loss (point of relative water economy) was highest for the Zebra (19.1 °C), lower for Double-barred (16.4 °C) and Painted (15.2 °C) and lowest for Red-Browed (4.1 °C) Finches, corresponding with their general patterns of habitat aridity. The point of relative water economy may be a sensitive index for assessing a species’ tolerance of aridity because it integrates individual physiological variables. We conclude that the Zebra Finch is not a physiological outlier amongst Australian finches, but is at the end of a continuum of aridity tolerance for the four study species.

A test for meiotic drive in hybrids between Australian and Timor zebra finches.

Meiotic drivers have been proposed as a potent evolutionary force underlying genetic and phenotypic variation, genome structure, and also speciation. Due to their strong selective advantage, they are expected to rapidly spread through a population despite potentially detrimental effects on organismal fitness. Once fixed, autosomal drivers are cryptic within populations and only become visible in between‐population crosses lacking the driver or corresponding suppressor. However, the assumed ubiquity of meiotic drivers has rarely been assessed in crosses between populations or species. Here we test for meiotic drive in hybrid embryos and offspring of Timor and Australian zebra finches—subspecies that have evolved in isolation for about two million years—using 38,541 informative transmissions of 56 markers linked to either centromeres or distal chromosome ends. We did not find evidence for meiotic driver loci on specific chromosomes. However, we observed a weak overall transmission bias toward Timor alleles at centromeres in females (transmission probability of Australian alleles of 47%, nominal p = 6 × 10–5). While this is in line with the centromere drive theory, it goes against the expectation that the subspecies with the larger effective population size (i.e., the Australian zebra finch) should have evolved the more potent meiotic drivers. We thus caution against interpreting our finding as definite evidence for centromeric drive. Yet, weak centromeric meiotic drivers may be more common than generally anticipated and we encourage further studies that are designed to detect also small effect meiotic drivers.

Water restriction influences intra-pair vocal behavior and the acoustic structure of vocalisations in the opportunistically breeding zebra finch (Taeniopygia guttata)

Seasonally-breeding species experience significant and predictable shifts in vocal behaviour; however, it is unclear to what extent this is true for species that breed opportunistically. The Australian zebra finch is an opportunistically breeding species, which means individuals must time breeding bouts based on many environmental factors. Here we tested the effect of experimental water restriction, which suppresses reproductive readiness in zebra finches, on vocal behaviour of males and females. More specifically, we quantified the effect of water restriction on three parameters of vocal behaviour in pair-bonded zebra finches: vocal activity, patterns of vocal exchanges, and the acoustic structure of vocalisations (calls and male song). We found that water restriction caused a decrease in vocal output (both song and call rate). Additionally, water restriction affected the composition of male songs. However, there was no effect of water restriction on the patterns of calling exchanges for monogamous partners (temporal coordination and turn taking). Finally, water restriction had vocalisation- and sex-specific effects on the acoustic structure of song syllables and calls. Because the direction of these effects were vocalisation- and sex- specific, there may be different mechanisms underlying the effects of water restriction on acoustic structure depending on context. These results contribute to the growing body of research highlighting the rich communicative potential of bird calls. Our current results raise the hypothesis that zebra finches may use changes in vocal behaviour and/or the structure of vocalisations of their conspecifics when making breeding decisions.

Susceptibility and Antibody Response of the Laboratory Model Zebra Finch (Taeniopygia guttata) to West Nile Virus.

Since the introduction of West Nile virus (WNV) into North America in 1999 a number of passerine bird species have been found to play a role in the amplification of the virus. Arbovirus surveillance, observational studies and experimental studies have implicated passerine birds (songbirds, e.g., crows, American robins, house sparrows, and house finches) as significant reservoirs of WNV in North America, yet we lack a tractable passerine animal model for controlled studies of the virus. The zebra finch (Taeniopygia guttata) serves as a model system across a diversity of fields, and here we develop the zebra finch a songbird model for WNV. Like many natural hosts of WNV, we found that zebra finches developed sufficient viremia to serve as a competent host, yet in general resisted mortality from infection. In the Australian zebra finch (AZF) T. g. castanotis, we detected WNV in the majority of sampled tissues by 4 days post injection (dpi). However, WNV was not detected in tissues of sacrificed birds at 14 dpi, shortly after the development of detectable anti-WNV antibodies in the majority of birds indicating successful viral clearance. We compared susceptibility between the two zebra finch subspecies AZF and Timor zebra finch (TZF) T. g. guttata. Compared to AZF, WNV RNA was detected in a larger proportion of challenged TZF and molecular detection of virus in the serum of TZF was significantly higher than in AZF. Given the observed moderate host competence and disease susceptibility, we suggest that zebra finches are appropriate as models for the study of WNV and although underutilized in this respect, may be ideal models for the study of the many diseases carried and transmitted by songbirds.

Fitness consequences of polymorphic inversions in the zebra finch genome

BackgroundInversion polymorphisms constitute an evolutionary puzzle: they should increase embryo mortality in heterokaryotypic individuals but still they are widespread in some taxa. Some insect species have evolved mechanisms to reduce the cost of embryo mortality but humans have not. In birds, a detailed analysis is missing although intraspecific inversion polymorphisms are regarded as common. In Australian zebra finches (Taeniopygia guttata), two polymorphic inversions are known cytogenetically and we set out to detect these two and potentially additional inversions using genomic tools and study their effects on embryo mortality and other fitness-related and morphological traits.ResultsUsing whole-genome SNP data, we screened 948 wild zebra finches for polymorphic inversions and describe four large (12–63 Mb) intraspecific inversion polymorphisms with allele frequencies close to 50 %. Using additional data from 5229 birds and 9764 eggs from wild and three captive zebra finch populations, we show that only the largest inversions increase embryo mortality in heterokaryotypic males, with surprisingly small effect sizes. We test for a heterozygote advantage on other fitness components but find no evidence for heterosis for any of the inversions. Yet, we find strong additive effects on several morphological traits.ConclusionsThe mechanism that has carried the derived inversion haplotypes to such high allele frequencies remains elusive. It appears that selection has effectively minimized the costs associated with inversions in zebra finches. The highly skewed distribution of recombination events towards the chromosome ends in zebra finches and other estrildid species may function to minimize crossovers in the inverted regions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-1056-3) contains supplementary material, which is available to authorized users.

Waltzing Taeniopygia: integration of courtship song and dance in the domesticated Australian zebra finch

Multimodal signalling can improve or maximize information exchange. A challenge is to show that two independent signals, such as vocalizations and visual displays, are deliberately coordinated. Male zebra finches, Taeniopygia guttata, signal visually and acoustically during courtship, performing a stereotyped dance while singing. The male approaches the female hopping in a zig-zag pattern, turning his body axis, and wiping his beak repeatedly on or above the perch. The only previous quantitative study of song and dance choreography in zebra finches revealed that the distribution of all movements during song was not strongly patterned across birds but very similar in fathers and sons. This raises the possibility that particular movements may follow a choreography. Here we report that three operationally defined dance movements, ‘beak wipe’ (BA), ‘turn-around’ (TA) and ‘hop’, occurred with different frequencies and speed during singing than during silence. BW, TA and hops clustered significantly at the start and end of song bouts and were arranged in a nonrandom fashion. In addition, BW, but not TA, were performed faster during song than nonsong. Finally, hops coincided significantly more often than expected by chance with particular notes. Together, these results suggest that male zebra finches integrate their song and dance during courtship. This may help females to identify courting males in a noisy environment and evaluate the intensity and quality of the courtship performance. Our results underscore that the choreography of movement gestures with learned vocalizations, such as hand gestures accompanying speech, is a further parallel between human and avian signalling. They invite future investigations into the underlying neural mechanisms and consequences for mate choice.

High major histocompatibility complex class I polymorphism despite bottlenecks in wild and domesticated populations of the zebra finch (Taeniopygia guttata).

BackgroundTwo subspecies of zebra finch, Taeniopygia guttata castanotis and T. g. guttata are native to Australia and the Lesser Sunda Islands, respectively. The Australian subspecies has been domesticated and is now an important model system for research. Both the Lesser Sundan subspecies and domesticated Australian zebra finches have undergone population bottlenecks in their history, and previous analyses using neutral markers have reported reduced neutral genetic diversity in these populations. Here we characterize patterns of variation in the third exon of the highly variable major histocompatibility complex (MHC) class I α chain. As a benchmark for neutral divergence, we also report the first mitochondrial NADH dehydrogenase 2 (ND2) sequences in this important model system.ResultsDespite natural and human-mediated population bottlenecks, we find that high MHC class I polymorphism persists across all populations. As expected, we find higher levels of nucleotide diversity in the MHC locus relative to neutral loci, and strong evidence of positive selection acting on important residues forming the peptide-binding region (PBR). Clear population differentiation of MHC allele frequencies is also evident, and this may be due to adaptation to new habitats and associated pathogens and/or genetic drift. Whereas the MHC Class I locus shows broad haplotype sharing across populations, ND2 is the first locus surveyed to date to show reciprocal monophyly of the two subspecies.ConclusionsDespite genetic bottlenecks and genetic drift, all surveyed zebra finch populations have maintained high MHC Class I diversity. The diversity at the MHC Class I locus in the Lesser Sundan subspecies contrasts sharply with the lack of diversity in previously examined neutral loci, and may thus be a result of selection acting to maintain polymorphism. Given uncertainty in historical population demography, however, it is difficult to rule out neutral processes in maintaining the observed diversity. The surveyed populations also differ in MHC Class I allele frequencies, and future studies are needed to assess whether these changes result in functional immune differences.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0546-3) contains supplementary material, which is available to authorized users.

Manipulating the perceived opportunity to cheat: an experimental test of the active roles of male and female zebra finches in mate guarding behavior

Birds are commonly sexually promiscuous, which can lead to conflict between the sexes and the evolution of paternity assurance strategies, such as mate guarding. Adaptive explanations for mate guarding have tended to focus on fitness consequences for males, but mate guarding and participation in being guarded is also likely adaptive for females in certain contexts. To better understand the adaptive explanations for mate guarding as well as the observed variation in paternity patterns, it is necessary to explore the relative costs and benefits of guarding (and being guarded) from both the male and female perspective. To investigate these costs and benefits, we conducted an experiment with the Australian zebra finch (Teniopygia guttata) in which we independently varied the perceived opportunity for each member of a captive breeding pair to engage in extra-pair copulation (EPC) solicitation behavior; as an individual’s EPC opportunity increased, the partner’s EPC opportunity remained constant. Our results indicate that, for males, mate guarding intensity increases when their female’s EPC opportunity increases but decreases when their own (i.e., male) EPC opportunity increases. We did not find evidence of flexible female guarding behavior, but we found that females do not evade their partners more as female EPC opportunity increases.

Potential roles for GNIH and GNRH-II in reproductive axis regulation of an opportunistically breeding songbird

The ability to breed at any time of year enables opportunistically breeding species to respond to good conditions whenever they occur. We investigate the neuroendocrine basis for this relatively unusual reproductive pattern in the avian world. One proposed mechanism for year-round breeding ability is tonic activation of gonadotropin-releasing hormone-I (GnRH-I) production that is flexibly modified by gonadotropin-inhibitory hormone (GnIH) production during unfavorable conditions. GnIH could inhibit GnRH secretion from the hypothalamus and/or inhibit GnRH action on the anterior pituitary gland. We studied neuroendocrine patterns in wild Australian zebra finches ( Taeniopygia guttata) sampled during a breeding period in Southern Australia, a non-breeding period in central Australia, and in juvenile males in the latter location. We asked whether patterns in immunoreactivity of three neuropeptides important for reproductive axis regulation, GnRH-I, GnRH-II and GnIH, during periods of breeding and non-breeding reflect this flexibility. We found that the numbers and sizes of immunoreactive (-ir) GnRH-I cells did not vary between breeding stages and ages. Contrary to our predictions, irGnIH cell number and size, as well as the synthesis of GnIH mRNA were similar in breeding and non-breeding conditions. However, breeding males had more and larger irGnRH-II cells in the midbrain compared to non-breeding males. Hence, while changes in irGnIH cells are not associated with fluctuations in gonadotropin secretion or gonad volume, the regulation of irGnRH-II cells might represent a previously-unidentified mechanism by which reproductive flexibility can be achieved; namely via behavioral neurotransmitter actions of GnRH-II rather than through the typical sensory-CNS integration-GnRH-I route.

Distribution and sexually dimorphic expression of steroid receptor coactivator-1 (SRC-1) in the zebra finch brain

Coactivator proteins, such as steroid receptor coactivator-1 (SRC-1) greatly enhance gene expression by amplifying steroid-induced transcription regulated by receptors such as estrogen receptor. These proteins may also play a role in the development of sex differences in central nervous system as well the maintenance of the sexually dimorphic behaviors in adulthood. One well-studied sexually dimorphic behavior is singing in songbirds such as the Australian zebra finch ( Taeniopygia guttata). Song learning and production is controlled by the song control system, a collection of sexually dimorphic nuclei found in the avian telencephalon. While the actions of steroid hormones on song nuclei development has been under debate, steroids, such as testosterone, influence singing behavior in adulthood. We hypothesize that the differential expression of coactivators in male and female brains aid in organizing the song nuclei during development and function in adulthood to aid in activating the song control nuclei to induce singing behavior. The distribution of SRC-1-immunoreactive neurons was localized in the brains of male and female zebra finches on the day of hatch (P1) and in adults. In adults SRC-1 immunoreactive cells are found in the four main song control nuclei as well as other steroid sensitive brain regions. We found that SRC-1 is sexually dimorphic in the adult zebra finch telencephalon, suggesting that coactivators may play a role in the maintenance of sexually dimorphic behaviors including singing.

Hatching asynchrony and growth trade-offs within domesticated and wild zebra finch, Taeniopygia guttata, broods

The Australian zebra finch, Taeniopygia guttata, is a widely used model organism, yet few studies have compared domesticated and wild birds with the aim of examining its relevance as an evolutionary model species. Domestic and wild broods hatch over approximately 4 and 2 days, respectively, which is important given that nestlings can fledge after as little as 12 days, although 16–18 days is common. We aimed to evaluate the extent to which the greater hatching asynchrony in domestic stock may effect reproductive success through greater variance in size hierarchies, variance in within-brood growth rates, and partial brood mortality. Therefore, by simultaneously controlling brood sizes and experimentally manipulating hatching intervals in both domesticated and wild birds, we investigated the consequences of hatching intervals for fledging success and nestling growth patterns, as well as trade-offs. Fledging success was similarly high in domestic and wild broods of either hatching pattern. Nonetheless, between-brood analyses revealed that domestic nestlings had significantly higher masses, larger skeletal characters, and longer wings than their wild counterparts, although wild nestlings had comparable wing lengths at the pre-fledging stage. Moreover, within-brood analyses revealed only negligible differences between domestic and wild nestlings, and larger effects of hatching order and hatching pattern. Therefore, despite significant differences in the hatching intervals, and the ultimate size achieved by nestlings, the domestication process does not appear to have significantly altered nestling growth trade-offs. The present study provides reassuring evidence that studies involving domesticated zebra finches, or other domesticated model organisms, may provide reasonable adaptive explanations in behavioural and evolutionary ecology.

The selective estrogen receptor-alpha coactivator, RPL7, and sexual differentiation of the songbird brain

The brain and behavior of the Australian zebra finch (Taeniopygia guttata) are sexually dimorphic. Only males sing courtship songs and the regions of the brain involved in the learning and production of song are significantly larger in males than females. Therefore the zebra finch serves as an excellent model for studying the mechanisms that influence brain sexual differentiation, and the majority of past research on this system has focused on the actions of steroid hormones in the development of these sex differences. Coregulators, such as coactivators and corepressors, are proteins and RNA activators that work by enhancing or depressing the transcriptional activity of the nuclear steroid receptor with which they associate, and thereby modulating the development of sex-specific brain morphologies and behaviors. The actions of these proteins may help elucidate the hormonal mechanisms that underlie song nuclei development. Research described in this review focus on the role of estrogen receptor coactivators in the avian brain; more specifically we will focus on the role of RPL7 (ribosomal protein L7; also known as L7/SPA) on sexual differentiation of the zebra finch song system. Collectively, these studies provide information about the role of steroid receptor coactivators on development of the zebra finch song system as well as on sexual differentiation of brain.

Short‐ and long‐term consequences of early developmental conditions: a case study on wild and domesticated zebra finches

Divergent selection pressures among populations can result not only in significant differentiation in morphology, physiology and behaviour, but also in how these traits are related to each other, thereby driving the processes of local adaptation and speciation. In the Australian zebra finch, we investigated whether domesticated stock, bred in captivity over tens of generations, differ in their response to a life-history manipulation, compared to birds taken directly from the wild. In a 'common aviary' experiment, we thereto experimentally manipulated the environmental conditions experienced by nestlings early in life by means of a brood size manipulation, and subsequently assessed its short- and long-term consequences on growth, ornamentation, immune function and reproduction. As expected, we found that early environmental conditions had a marked effect on both short- and long-term morphological and life-history traits in all birds. However, although there were pronounced differences between wild and domesticated birds with respect to the absolute expression of many of these traits, which are indicative of the different selection pressures wild and domesticated birds were exposed to in the recent past, manipulated rearing conditions affected morphology and ornamentation of wild and domesticated finches in a very similar way. This suggests that despite significant differentiation between wild and domesticated birds, selection has not altered the relationships among traits. Thus, life-history strategies and investment trade-offs may be relatively stable and not easily altered by selection. This is a reassuring finding in the light of the widespread use of domesticated birds in studies of life-history evolution and sexual selection, and suggests that adaptive explanations may be legitimate when referring to captive bird studies.

Neuroscience of birdsong

Neuroscience of birdsong

Opportunism at work: habitat predictability affects reproductive readiness in free‐living zebra finches

SummaryOpportunistic breeding (i.e. breeding whenever favourable conditions occur, regardless of interval or periodicity) is a strategy often adopted by animals breeding in habitats where food resources important for offspring survival are unpredictable.One putative adaptation for this breeding strategy is the maintenance of a partially activated reproductive system year‐round. Breeding readiness is assumed to be the default state and reproduction is therefore suppressed only when environmental conditions become inhibitory.We tested this assumption in an opportunistic archetype, the Australian zebra finchTaeniopygia guttata, by comparing reproductive activation and suppression in free‐living zebra finches in two climatically different habitats: (1) an unpredictable habitat of arid central Australia, where breeding is closely tied to aperiodic rainfall and can occur during any month of the year, and (2) a more predictably seasonal habitat in southern Australia, where breeding occurs during approximately the same months each year. We quantified reproductive activation by measuring gonad size and circulating gonadotrophin concentration during the breeding and nonbreeding seasons in the predictable habitat and within a nonbreeding period during drought in the unpredictable habitat.We found reproductive readiness changed consistently between the breeding and nonbreeding state in the predictable habitat, but more nonbreeding birds in the unpredictable habitat maintained an activated reproductive system even though they had poorer body condition. We found no evidence for suppression of reproductive activity by stress hormones (i.e. elevated glucocorticoids). Furthermore, birds were able to activate the reproductive axis quickly when removed from inhibitory field conditions and responded equally well to various stimulatory cues.

Geographic and Temporal Variation of the Male Zebra Finch Distance Call

AbstractTemporal and geographic variation of acoustic signals can provide insights into dispersal patterns, population history and speciation. Vocalizations that are transmitted from one generation to the next are of particular value in this respect because they can reveal patterns of gene flow, effectively behaving as population markers. The male zebra finchTaeniopygia guttatadistance call is one such vocalization; sons learn their father's distance call in the first 40 d of life and it is individually stereotyped thereafter. We investigated geographic variation in the zebra finch by comparing the structure of distance calls recorded from 61 males from six populations across the continent‐wide range of the Australian subspeciesT. g. castanotis. Intra‐population variation was high, in many cases greater than the variation among all males recorded, possibly because of population interchange. However, three of six call variables measured, including the newly discovered modulated element, varied geographically although the pattern of distance call variation did not agree with that of geographic proximity of populations. The proportion of calls with a modulated element increased dramatically over 7 yr in central Australia but there was no change over a similar period of time in south‐eastern Australia where no calls contained the element. The findings suggest that interchange among widely separated populations may be commonplace in Australian zebra finches, with the possible exception of those from south‐eastern Australia.

Behavioral and adrenocortical responses to mate separation and reunion in the zebra finch

The adaptive value of social affiliation has been well established. It is unclear, however, what endogenous mechanisms may mediate affiliative behavior. The Australian zebra finch ( Taeniopygia guttata) breeds colonially and adults maintain lifelong pair bonds that may be disrupted in the wild due to high mortality rates. Many of its natural, social behaviors are maintained in laboratory conditions, making this species well suited for studying the mechanisms of affiliation. This study examines the behavioral and neuroendocrine responses to pair mate separation and reunion in zebra finches. We measured plasma corticosterone (CORT) and behavioral changes following separation from a pair bonded mate, and again upon reintroducing the mate or an opposite-sex cagemate. Plasma CORT concentrations were: (1) elevated during pair mate separation, even in the presence of other same-sex individuals, and (2) reduced to baseline upon reunion with the pair mate but not upon re-pairing with a new opposite-sex partner. These findings show that zebra finches exhibit hormonal responses to separation and reunion specifically with a bonded pair mate and not with other familiar conspecifics. In addition, alterations in behavior during separation and reunion are consistent with monogamous pair bond maintenance. This study presents evidence for adrenocortical involvement in avian pair bonding, and for hypothalamic–pituitary–adrenal activation in response to an ecologically relevant social stressor.

Effects of Band Color on Survivorship, Body Condition and Reproductive Effort of Free-Living Australian Zebra Finches

Effects of Band Color on Survivorship, Body Condition and Reproductive Effort of Free-Living Australian Zebra Finches