Survivorship, dispersal and sex ratios of Zebra Finches Taeniopygia guttata in southeast Australia

Membership of three permanent breeding colonies of Zebra Finches Taeniopygia guttata studied in farmland changed continually due to arrival and departure of birds from distant colonies. Sixty-six percent of adults stayed for less than 1 month, and many that stayed longer disappeared for extended periods. Over 78% of adults captured were hatched in other colonies and only 23% made a breeding attempt in their natal colony. There was no sex-biased natal dispersal or philopatry, but there were sex differences in the timing of dispersal. Sex ratios at the end of parental care were variable and may depend on food resources. Adult ratios were slightly male-biased. Annual losses of adults ranged from 72 to 82% across colonies, but mortalities and dispersal were heavily confounded by high adult mobility. The oldest bird was more than 5 years old. A total of 67% of young were lost between fledging and nutritional independence at 35 days of age, and only 20% of fledglings survived to day 80, the age of first breeding. Artificial supplies of seed at baited walk-in traps prolonged the stay of dispersing adults from other colonies, enhanced the survivorship of young hatched in the colony and possibly affected the secondary sex ratio. In this southeast part of their Australia-wide distribution, Zebra Finch populations appear to be highly mobile over a very large home range with extensive free interchange of members among a number of permanent breeding colonies. High mobility may be adaptive for exploiting patches of seed and water in a highly erratic environment.     

Triploid ZZZ Zebra Finches Taeniopygia guttata exhibit abnormal sperm heads and poor reproductive performance

Here we report the first discovery of two viable triploid male Zebra Finches Taeniopygia guttata. We compared the morphology of their sperm with that of normal diploid Zebra Finches and examined eggs resulting from a triploid male and diploid female pairing to investigate whether triploid Zebra Finches can reproduce. The majority (78%) of the triploids' spermatozoa had malformed sperm heads, which were 60% larger, and all examined eggs (n = 42) were infertile. Our results tentatively suggest that triploid ZZZ Zebra Finches cannot reproduce, and thus represent a rare evolutionary dead‐end.     

Personality and body condition have additive effects on motivation to feed in Zebra Finches Taeniopygia guttata

Several hypotheses have been proposed to account for the adaptive evolution of personality, defined as inter‐individual differences in behaviour that are consistent over time and across situations. For instance, the ‘pace‐of‐life syndrome’ hypothesis suggests that personality evolved as a behavioural correlate of life‐history trajectories that vary within populations. Thus, proactivity, corresponding to higher exploratory tendencies or higher boldness levels, has been linked to higher productivity or mortality rates. However, the extent to which proactivity is associated with a higher motivation to forage remains poorly understood. Moreover, although personality and its effects on foraging behaviour are usually considered to be independent of any motivational or nutritional state, few studies so far have challenged this. Here we show that personality traits, both individually or combined using a principal component analysis, and body condition have additive effects on latency to feed following food deprivation in the Zebra Finch Taeniopygia guttata, with personality accounting for 41% and body condition for about 20% of the total variation in latency to feed. In accordance with the pace‐of‐life syndrome hypothesis, latency to feed was negatively related to the degree of proactivity and positively related to body condition. Thus, proactive individuals and individuals in poorer condition were quicker to start feeding after a period of food deprivation. The absence of a significant interaction between personality and body condition further suggests that the effect of personality was independent of body condition. We discuss the relevance of our results in relation to the different factors influencing foraging in birds. Moreover, we place our results within a life‐history framework by emphasizing the correlated evolution of life‐history traits and personality.     

Do Female Zebra Finches,Taeniopygia guttata,Choose Their Mates Based on Their ‘Personality’?

A major challenge in behavioural and evolutionary ecology is to understand the evolution and maintenance of consistent behavioural differences among individuals within populations, often referred to as animal ‘personalities’. Here, we present evidence suggesting that sexual selection may act on such personality differences in zebra finches (Taeniopygia guttata), as females seem to choose males on the basis of their exploratory behaviour per se, while taking into account their own personality. After observing a pair of males, whose apparent levels of exploration were experimentally manipulated, females that exhibited low‐exploratory tendencies showed no preference during mate choice for males that had appeared to be either ‘exploratory’ or ‘unexploratory’. In contrast, intermediate and highly exploratory females preferred apparently exploratory males over apparently unexploratory ones. Our results suggest that behavioural or genetic compatibility for personality traits might be important for mate choice, at least for exploratory individuals.     

Intra‐specific variance in sperm morphometry: a comparison between wild and domesticated Zebra Finches Taeniopygia guttata

The Zebra Finch Taeniopygia guttata is a model bird species for the experimental study of behavioural and evolutionary concepts in captivity and especially sexual selection. The validity of sexual selection studies of domesticated birds is of long‐standing concern as little is known about the influence of domestication on sexually selected traits. Most domesticated Zebra Finch populations are maintained under a strict breeding regime to avoid potential inbreeding. However, these breeding regimes may interfere with the processes of sexual selection and influence the evolution of sexually selected traits because they may limit or prohibit active mate choice. Here, we investigated the potential impact of a monogamous breeding scheme in a domesticated population in which active mate choice is largely inhibited, on the evolution of sperm morphometry as a sexually selected trait. We compared sperm morphometric traits (total sperm length and length of sperm head, midpiece and flagellum), and the variance thereof, between a domesticated and two wild Zebra Finch populations. Although we found significant differences between the three populations for certain sperm traits (head length, midpiece length), which may be of importance in postcopulatory sexual selection, overall, variance in sperm morphometry did not differ between the domesticated and the wild Zebra Finch populations. Our results validate the use of domesticated Zebra Finches for further studies of postcopulatory sexual selection and sperm competition.     

The Strength of Species Recognition in Captive Female Zebra Finches (Taeniopygia guttata): A Comparison Across Estrildid Heterospecifics

Conspecific recognition is essential for sexually reproducing species. Captive zebra finches ( Taeniopygia guttata ) are a model system in which the behavioural, ontogenetic and neurobiological bases of own-species (conspecific) recognition have been studied in detail. To assess the potential role of phylogeographic effects on species recognition, we examined the spatial preferences of unmated captive-bred female zebra finches between unfamiliar captive males of conspecific and estrildid heterospecific male stimuli. In accordance with prior studies using domesticated Bengalese finches ( Lonchura striata vars. domestica ), we found significant spatial and behavioural preference for conspecific males by female zebra finches, irrespective of heterospecific male phylogeographic origin mating status, or individual behaviour. This result has ramifications for the interpretation of social and mate preferences in this model species as it implies a consistency of species discrimination by captive female zebra finches.     

Fine structural basis of the cutaneous water barrier in nestling Zebra Finches Poephila guttata

Transepidermal water loss was studied in nestlings, fledglings and adults of the xerophylic Zebra Finch Poephila guttata. Nestlings lose little water (2–4 ppm/0–5 cm²/h) through the skin as compared to adults (60–70 ppm/0–5 cm²/h). Light and electron microscopic examination of the skin sections of both age classes revealed an abundance of lipids in the form of vacuoles and large multigranular bodies in the epidermis of nestlings, but few such lipid bodies in the epidermis of adults. Some of the disc-like contents of granular bodies appear to be extruded into the intercellular spaces. Based on earlier studies with mammals and reptiles, it is concluded that epidermal lipids are the basis of the integumentary permeability barrier in nestlings.     

The use of muscle protein for egg production in the Zebra Finch Taeniopygia guttata

Pectoral muscle can be an important source of protein for birds. During egg formation Zebra Finches Taeniopygia guttata are able to compensate for nutritional inadequacies in their diet by utilization of the protein in their flight muscles. This analysis of flight muscle sarcoplasm supported earlier observations of protein depletion during egg production. However, SDS gel electrophoresis of the sarcoplasm produced no evidence to support a previous suggestion of the existence of a high molecular weight storage protein, and it is thought that the original observation may have arisen as an artefact of experimental methodology. During laying, protein removal from the sarcoplasm occurred over a range of different proteins and was not confined to any one specific protein band. Additionally, the protein band most reduced over the course of laying did not contain elevated levels of the amino acids most limiting to egg production. These results indicate that during laying, flight muscle sarcoplasm contributes towards the nutrient requirements of egg production from general protein reserves, rather than from a specific storage protein containing elevated levels of limiting amino acids.     

Discovery of the First Germline-Restricted Gene by Subtractive Transcriptomic Analysis in the Zebra Finch,Taeniopygia guttata

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The importance of green seed in the nitrogen nutrition of the Zebra Finch Taeniopygia guttata

Abstract Australian grass-finches are widely reported to consume large quantities of green seed when it becomes available, and the opportunistic breeding of wild Zebra Finches in the arid zone has been correlated with the occurrence of rain. In this study, green and ripe seeds were harvested from seven pasture and weed grasses grown in experimental plots and, along with three cereal flours and whole-egg powder, were analysed for the amino-acid composition of their protein. The relative levels of ten amino acids essential in the diets of growing birds were compared between samples using a cluster analysis dendrogram generated from Raabe's Similarity Index. The protein of all green seeds clustered with whole egg, and away from all but one of the ripe seeds and seed products. Green and ripe seed profiles were found to be significantly different by a two-sample multivariate test of significance (Hotelling's T²). Histidine, lysine, phenylalanine and threonine were the amino acids most different. Of these four amino acids, lysine and threonine (along with methionine) were potentially limiting in ripe seeds when compared with whole-egg protein. In green seeds, lysine was only marginally limiting, threonine was no longer limiting, but methionine was still limiting when compared with whole-egg protein. These results indicate that the benefit of green vs ripe seed in the diet of breeding Zebra Finches is partly a higher level of the limiting essential amino acid, lysine, and partly a higher intake and throughput of soft green seed and consequent greater extraction of limiting essential amino acids.     

Genetic correlation between resting metabolic rate and exploratory behaviour in deer mice (Peromyscus maniculatus)

According to the 'pace-of-life' syndrome hypothesis, differences in resting metabolic rate (RMR) should be genetically associated with exploratory behaviour. A large number of studies reported significant heritability for both RMR and exploratory behaviour, but the genetic correlation between the two has yet to be documented. We used a quantitative genetic approach to decompose the phenotypic (co)variance of several metabolic and behavioural measures into components of additive genetic, common environment and permanent environment variance in captive deer mice. We found significant additive genetic variance for two mass-independent metabolic measures (RMR and the average metabolic rate throughout the respirometry run) and two behavioural measures (time spent in centre and distance moved in a novel environment). We also detected positive additive genetic correlation between mass-independent RMR and distance moved (r(A) = 0.78 ± 0.23). Our results suggest that RMR and exploratory behaviour are functionally integrated traits in deer mice, providing empirical support for one of the connections within the pace-of-life syndrome hypothesis.     

Temporal variation in constitutive and inducible heat shock proteins in the Zebra Finch Taeniopygia guttata

Cellular stressors initiate the heat shock response mediated by heat shock proteins (HSPs). There are two main types of HSPs, constitutive (always expressed) and inducible (upon stress), but as many in vivo studies fail to distinguish between them and because temporal expression patterns often differ among various types of HSPs, it is unclear when to measure HSPs. In this study, 26 (13 per treatment) adult female Zebra Finches Taeniopygia guttata were heat‐stressed (39 °C) or placed in a control brooder (room temperature) for 3 h and were bled 1 week prior to and at 1, 2, 4, 6 and 20 h post‐treatment. Treatment had no effect on levels of either constitutive HSP70 or inducible HSP90, but both HSPs decreased with time relative to baseline, suggesting a possible effect of handling stress and/or circadian variation.     

The measurement of resting metabolic rate in preschool children

Objective: This study examined the repeatability of measuring resting metabolic rate (RMR) in preschool children and the effect of different calculation protocols. Research Methods and Procedures: Eleven children (4 females and 7 males) participated in the project. They were recruited through advertisements in local schools and community centers. Resting metabolic rate was measured on 3 occasions over a 2‐week period, each after an overnight fast and each lasting ～20 to 25 minutes. Results were compared using repeated‐measures ANOVA to check for repeatability, and a number of methods of calculating RMR were assessed. Results: Repeatability of RMR measurements was good (coefficient of variation of replicates, 6.8%), with no significant difference between days of measurement. The lowest RMR measurement was obtained when the first 10 minutes were excluded and periods during which large activity was observed were excluded. This measurement was, on average, 4% lower than averaging the measurements after the first 5 minutes, including body movements. Discussion: This study suggests that RMR can be measured in preschool children and that the best method for calculating RMR in these subjects is to exclude periods when large body movements occur and the first 10 minutes of the measurement period. Only a single measurement of RMR is needed to obtain a reliable estimate.     

Egg development time in the Zebra Finch Taeniopygia guttata varies with laying order and clutch size

As female birds are able to lay no more than a single egg each day, in those species producing larger clutches the first laid eggs may get a developmental head‐start over later eggs in the clutch. All other things being equal, the differential pattern of development across the clutch may contribute to hatching asynchrony and subsequent inequity in the competition between brood mates, and ultimately increase variance in the quality and fitness of first‐ and last‐laid offspring. It has been suggested that females might allocate resources differently across the laying sequence to moderate the developmental rate and hatching time of different embryos. We tested this theory in the Zebra Finch Taeniopygia guttata, a common model species for investigating maternal effects in birds. We removed 758 eggs from 160 nests shortly after they were laid and used artificial incubators to control for parental effects and monitor hatching times. Eggs from larger clutches consistently hatched sooner than those from average‐sized clutches, demonstrating that the intrinsic properties of an egg can alter the developmental time of embryos. There were also differences in the development time of eggs across the laying sequence, but these patterns were weaker, inconsistent and unrelated to sequential investment across the laying sequence in a straightforward way. This study indicates that maternal resource allocation to eggs across the laying sequence and across clutch sizes can influence development times and play a potentially important role in determining the competitive dynamics of broods.     

Nucleotide Variation, Linkage Disequilibrium and Founder-Facilitated Speciation in Wild Populations of the Zebra Finch (Taeniopygia guttata)

The zebra finch has long been an important model system for the study of vocal learning, vocal production, and behavior. With the imminent sequencing of its genome, the zebra finch is now poised to become a model system for population genetics. Using a panel of 30 noncoding loci, we characterized patterns of polymorphism and divergence among wild zebra finch populations. Continental Australian populations displayed little population structure, exceptionally high levels of nucleotide diversity (π = 0.010), a rapid decay of linkage disequilibrium (LD), and a high population recombination rate (ρ ≈ 0.05), all of which suggest an open and fluid genomic background that could facilitate adaptive variation. By contrast, substantial divergence between the Australian and Lesser Sunda Island populations (K_ST = 0.193), reduced genetic diversity (π = 0.002), and higher levels of LD in the island population suggest a strong but relatively recent founder event, which may have contributed to speciation between these populations as envisioned under founder-effect speciation models. Consistent with this hypothesis, we find that under a simple quantitative genetic model both drift and selection could have contributed to the observed divergence in six quantitative traits. In both Australian and Lesser Sundas populations, diversity in Z-linked loci was significantly lower than in autosomal loci. Our analysis provides a quantitative framework for studying the role of selection and drift in shaping patterns of molecular evolution in the zebra finch genome.     

Features of the Retinotopic Representation in the Visual Wulst of a Laterally Eyed Bird,the Zebra Finch (Taeniopygia guttata)

The visual wulst of the zebra finch comprises at least two retinotopic maps of the contralateral eye. As yet, it is not known how much of the visual field is represented in the wulst neuronal maps, how the organization of the maps is related to the retinal architecture, and how information from the ipsilateral eye is involved in the activation of the wulst. Here, we have used autofluorescent flavoprotein imaging and classical anatomical methods to investigate such characteristics of the most posterior map of the multiple retinotopic representations. We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye. Horizontally, the visual field representation extended from -5° beyond the beak tip up to +125° laterally. Vertically, a small strip from -10° below to about +25° above the horizon activated the visual wulst. Although retinal ganglion cells had a much higher density around the fovea and along a strip extending from the fovea towards the beak tip, these areas were not overrepresented in the wulst map. The wulst area activated from the foveal region of the ipsilateral eye, overlapped substantially with the middle of the three contralaterally activated regions in the visual wulst, and partially with the other two. Visual wulst activity evoked by stimulation of the frontal visual field was stronger with contralateral than with binocular stimulation. This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye. The lack of a foveal overrepresentation suggests that identification of objects may not be the primary task of the zebra finch visual wulst. Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.     

Effect of calorie restriction on resting metabolic rate and spontaneous physical activity

Objective: It is unclear if resting metabolic rate (RMR) and spontaneous physical activity (SPA) decrease in weight‐reduced non‐obese participants. Additionally, it is unknown if changes in SPA, measured in a respiratory chamber, reflect changes in free‐living physical activity level (PAL). Research Methods and Procedures: Participants (N = 48) were randomized into 4 groups for 6 months: calorie restriction (CR, 25% restriction), CR plus structured exercise (CR+EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), low‐calorie diet (LCD, 890 kcal/d supplement diet until 15% weight loss, then weight maintenance), and control (weight maintenance). Measurements were collected at baseline, Month 3, and Month 6. Body composition and RMR were measured by DXA and indirect calorimetry, respectively. Two measures of SPA were collected in a respiratory chamber (percent of time active and kcal/d). Free‐living PAL (PAL = total daily energy expenditure by doubly labeled water/RMR) was also measured. Regression equations at baseline were used to adjust RMR for fat‐free mass and SPA (kcal/d) for body weight. Results: Adjusted RMR decreased at Month 3 in the CR group and at Month 6 in the CR+EX and LCD groups. Neither measure of SPA decreased significantly in any group. PAL decreased at Month 3 in the CR and LCD groups, but not in the CR+EX group, who engaged in structured exercise. Changes in SPA in the chamber and free‐living PAL were not related. Discussion: Body weight is defended in non‐obese participants during modest caloric restriction, evidenced by metabolic adaptation of RMR and reduced energy expenditure through physical activity.