Finch Populations Research Articles

Basal metabolic rate can evolve independently of morphological and behavioural traits

Quantitative genetic analyses of basal metabolic rate (BMR) can inform us about the evolvability of the trait by providing estimates of heritability, and also of genetic correlations with other traits that may constrain the ability of BMR to respond to selection. Here, we studied a captive population of zebra finches (Taeniopygia guttata) in which selection lines for male courtship rate have been established. We measure BMR in these lines to see whether selection on male sexual activity would change BMR as a potentially correlated trait. We find that the genetic correlation between courtship rate and BMR is practically zero, indicating that the two traits can evolve independently of each other. Interestingly, we find that the heritability of BMR in our population (h(2)=0.45) is markedly higher than was previously reported for a captive zebra finch population from Norway. A comparison of the two studies shows that additive genetic variance in BMR has been largely depleted in the Norwegian population, especially the genetic variance in BMR that is independent of body mass. In our population, the slope of BMR increase with body mass differs not only between the sexes but also between the six selection lines, which we tentatively attribute to genetic drift and/or founder effects being strong in small populations. Our study therefore highlights two things. First, the evolvability of BMR may be less constrained by genetic correlations and lack of independent genetic variation than previously described. Second, genetic drift in small populations can rapidly lead to different evolvabilities across populations.

Impacts of trichomonosis epidemics on Greenfinch Chloris chloris and Chaffinch Fringilla coelebs populations in Finland

Population consequences of parasites in wild birds are rarely documented. One exception is the decline of British finch populations due to an epidemic caused by the protozoan parasite Trichomonas gallinae. Finch trichomonosis has recently spread from the UK to northern Europe, but its consequences for local finch populations have not been studied. We assessed the extent to which the trichomonosis epidemic affected the Finnish population sizes of European Greenfinch Chloris chloris, Common Chaffinch Fringilla coelebs and a control species, Great Tit Parus major, and the body condition of Greenfinches. The disease was first documented in Finland in 2008 and epidemics were observed mainly in southwestern Finland. Greenfinches showed a significant decline of 47% in breeding numbers and 65% in wintering numbers in southern Finland during 2006–2010. Breeding Chaffinch numbers showed a slight decline (4%) during the same study period that was significant only in central Finland. Great Tit did not show a significant change in breeding numbers. During the initial disease epidemic the body condition of all demographic groups of Greenfinches decreased equally, which suggests that the disease was not selective in respect of age or sex. There were no encounters of Finnish‐ringed Greenfinches or Chaffinches in the UK, which could indicate that the parasite has not necessarily been transferred directly from the UK, but perhaps by migrants from Sweden and Germany.

House Finch Populations Differ in Early Inflammatory Signaling and Pathogen Tolerance at the Peak ofMycoplasma gallisepticumInfection

Host individuals and populations often vary in their responses to infection, with direct consequences for pathogen spread and evolution. While considerable work has focused on the mechanisms underlying differences in resistance-the ability to kill pathogens-we know little about the mechanisms underlying tolerance-the ability to minimize fitness losses per unit pathogen. Here, we examine patterns and mechanisms of tolerance between two populations of house finches (Haemorhous [formerly Carpodacus] mexicanus) with different histories with the bacterial pathogen Mycoplasma gallisepticum (MG). After infection in a common environment, we assessed two metrics of pathology, mass loss and eye lesion severity, as proxies for fitness. We calculated tolerance using two methods, one based on pathology and pathogen load at the peak of infection (point tolerance) and the other based on the integrals of these metrics over time (range tolerance). Alabama birds, which have a significantly longer history of exposure to MG, showed more pronounced point tolerance than Arizona birds, while range tolerance did not differ between populations. Alabama birds also displayed lower inflammatory cytokine signaling and lower fever early in infection. These results suggest that differences in inflammatory processes, which can significantly damage host tissues, may contribute to variation in tolerance among house finch individuals and populations. Such variation can affect pathogen spread and evolution in ways not predictable by resistance alone and sheds light on the costs and benefits of inflammation in wild animals.

Population Status of the Endangered Laysan Finch

Abstract The Laysan Finch (Telespiza cantans) is an endangered Hawaiian honeycreeper that occurs on only a few small islands in the northwestern Hawaiian Island Archipelago. Twenty-two years of recent population estimates (1991–2012) from Laysan Island were analyzed to ascertain the current status of this endangered species; the entire 44 years of census data available were then used to identify long-term population trends. Laysan Finch population estimates have exhibited extreme fluctuations that can be attributed at least in part to spring rainfall patterns. The average population size has remained at ∼10,000 individuals. The Poisson regression analysis conducted for the last 22 years indicates a slightly deceasing annual population trend. However, when all 44 years of data were included in a comprehensive trend analysis, a stable population trend was documented. These results highlight the importance of long-term data sets when monitoring small closed populations - a situation commonly encountered with...

Does hatching failure breed infidelity?

In socially monogamous species, the reasons for female infidelity are still controversial. It has been suggested that females could seek extra-pair copulations as an insurance against hatching failure caused by male infertility or incompatibility. In species where couples breed repeatedly, females could use previous hatching success as a cue to assess their partner’s infertility (or incompatibility). Hence, it has been predicted that females should increase their infidelity after experiencing hatching failures, but to our knowledge this hypothesis has never been tested experimentally. We manipulated hatching success of pairs in a captive population of zebra finches (Taeniopygia guttata), a species that forms lifelong pair bonds, and measured female willingness to engage in extra-pair copulation. By experimentally cross-fostering fertile and infertile eggs, couples either experienced 100% or about 35% hatching success in each of three consecutive clutches. Contrary to our prediction, females that experienced repeated hatching failure did not increase their responsiveness toward extra-pair males relative to those females with 100% hatching success. Moreover, there was no difference in female calling rate for the partner after male removal and no occurrence of divorce when the opportunity was given. These findings seem to contradict the common view that reproductive failure weakens the pair bond. Furthermore, a critical review of the literature suggests that there is no convincing evidence supporting this hypothesis in other species either. We therefore highlight that this fundamental area of behavioral ecology research is still much in need of specific experimental work that controls for confounding factors. Key words: divorce, extra-pair mating, fertility insurance, hatching failure, pair bond, zebra finch [Behav Ecol]

Bill Redness Is Positively Associated with Reproduction and Survival in Male and Female Zebra Finches

Sexual traits can serve as honest indicators of phenotypic quality when they are costly. Brightly coloured yellow to red traits, which are pigmented by carotenoids, are relatively common in birds, and feature in sexual selection. Carotenoids have been linked to immune and antioxidant function, and the trade-off between ornamentation and these physiological functions provides a potential mechanism rendering carotenoid based signals costly. Mutual ornamentation is also common in birds and can be maintained by mutual mate choice for this ornament or by a correlated response in one sex to selection on the other sex. When selection pressures differ between the sexes this can cause intralocus sexual conflict. Sexually antagonistic selection pressures have been demonstrated for few sexual traits, and for carotenoid-dependent traits there is a single example: bill redness was found to be positively associated with survival and reproductive output in male zebra finches, but negatively so in females. We retested these associations in our captive zebra finch population without two possible limitations of this earlier study. Contrary to the earlier findings, we found no evidence for sexually antagonistic selection. In both sexes, individuals with redder bills showed higher survival. This association disappeared among the females with the reddest bills. Furthermore, females with redder bills achieved higher reproductive output. We conclude that bill redness of male and female zebra finches honestly signals phenotypic quality, and discuss the possible causes of the differences between our results and earlier findings.

Provisioning habitat with custom‐designed nest‐boxes increases reproductive success in an endangered finch

AbstractManipulating resource availability to assess the strength and effects of resource limitation on an animal population is relatively straightforward, and thus, common in the scientific literature. Resource quality, however, is rarely manipulated, as this requiresa prioriknowledge of a relationship between some measurable variation in the resource and individual preference and/or fitness. Recent research on nest‐site selection was used to inform the design of custom‐built nest‐boxes for an endangered hollow‐nester, the Gouldian finch (Erythrura gouldiae). By provisioning breeding populations with these ‘high quality’ artificial nest sites over 3 years, we experimentally investigated the strength and effects of nest‐site limitation in this species. Breeding pairs using nest‐boxes initiated nesting earlier, produced larger clutches and fledged more offspring per season than those in natural hollows. Total and mean reproductive output also increased in nest‐box provisioned sites over the duration of the study. All of these effects were predominantly driven by pairs initiating clutches earlier, potentially because of the reduced intra‐ and interspecific competition for nest sites at optimal breeding times. Our findings suggest that reproduction in wild Gouldian finch populations may be limited by the availability of high quality nest sites in the landscape, and that nest‐boxes could be used as a tool for enhancing reproduction in recovering populations. Furthermore, we conclude that resource quality is equally, if not more important than quantity when supplementing resource‐limited habitats.

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

The Zebra FinchTaeniopygia guttatais 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.

Singing activity stimulates partner reproductive investment rather than increasing paternity success in zebra finches

Song is used as a signal in sexual selection in a wide range of taxa. In birds, males of many species continue to sing after pair formation. It has been suggested that a high song output after pair formation might serve to attract extra-pair females and to minimise their own partner’s interest in extra-pair copulations. A non-exclusive alternative function that has received only scant attention is that the amount of song might stimulate the own female’s investment into eggs in a quantitative way. We address these hypotheses in a captive population of zebra finches, Taeniopygia guttata, by relating male undirected song output (i.e. non-courtship song) to male egg siring success and female reproductive investment in two different set-ups. When allowed to breed in aviaries, males with the highest song output were no more attractive than others to females in an analysis of 4,294 extra-pair courtships involving 164 different males, and they also did not sire more offspring (both trends were against the expectation). When breeding in cages with two different partners subsequently, females produced larger eggs with more orange yolks when paired to a male with a high song output. These findings suggest that singing activity in paired zebra finch males might primarily function to stimulate the partner and not to attract extra-pair females.

Male song structure predicts reproductive success in a wild zebra finch population

The zebra finch is the model species for the study of the evolution of birdsong, female song preferences, song learning and the neural processes underlying song learning and production. Despite this, almost all work to date in these fields has focused on domesticated zebra finches in captivity and remarkably little is known about song preferences, or the reproductive success of males with different songs, in wild populations. In this study we tested, for the first time in a wild zebra finch population, whether a male’s song structure predicts his reproductive success. We recorded male songs in a nestbox population. Males from this wild population sang longer songs, with a higher peak frequency, than domesticated males. The number of each male’s offspring that survived until day 12 posthatching (a proxy for fledging success) was used as a measure of reproductive success. Nestlings were partially cross-fostered, allowing us to disentangle the indirect effects of male genetic quality or maternal effects from those of direct benefits such as parental care. Male song structure predicted the number of genetic offspring surviving, as well as hatching success, but not the number or size of eggs in a clutch. Song structure did not predict the number of unrelated foster-offspring that survived. These results provide the first evidence that differences in male song can predict differences in reproductive success in the zebra finch, and suggest that differences in genetic quality are responsible, rather than differences in parental care or maternal investment in the eggs.

QTL LINKAGE MAPPING OF ZEBRA FINCH BEAK COLOR SHOWS AN OLIGOGENIC CONTROL OF A SEXUALLY SELECTED TRAIT

Mate choice based on sexual ornaments can impose strong selection, which raises the question of how genetic variation in ornaments is maintained. One mechanism that has been proposed is genic capture. If ornament expression is influenced by general condition and condition is under polygenic control, selection will be inefficient in removing genetic variation. Here we analyze whether the genetic architecture of beak color in a population of zebra finches supports this hypothesis. Zebra finch beak color is commonly assumed to be under strong selection by mate choice, although some of the evidence is ambiguous. We show that beak redness has a heritability of 34% in our population and that it is strongly genetically correlated between the sexes, suggesting that it is largely controlled by the same genes in males and females. We mapped variation in beak redness based on 1404 single-nucleotide polymorphism (SNP) markers genotyped in a large pedigree. We find evidence for linkage on four chromosomes (Tgu1, Tgu5, Tgu13, Tgu21), which together explain a large part of the additive genetic variance. Our finding of genomic regions with major additive effects is not consistent with directional selection and genic capture, but rather suggests a role of antagonistic pleiotropy in maintaining genetic variation.

Pathogenicity and immunogenicity of three Mycoplasma gallisepticum isolates in house finches ( Carpodacus mexicanus)

Mycoplasma gallisepticum (MG) has become a common cause of conjunctivitis in free-living house finches ( Carpodacus mexicanus) since its emergence in the early 1990s. To date, temporal and spatial genotypic variation in MG has been documented, but phenotypic variation in pathogenicity and immunogenicity has not been examined. House finches were inoculated with MG isolates Virginia (VA)1994, California (CA)2006, or North Carolina (NC)2006, which were cultured from free-living house finches with conjunctivitis in 1994, 2006, and 2006, respectively. Infection with NC2006 resulted in the most severe eye lesions, highest pathogen loads, and highest levels of pathogen-specific lachrymal and serum antibodies. Infection with CA2006 caused the least severe eye lesions, lowest pathogen load, and lowest levels of antibodies. A small number of birds in each group developed protracted, severe disease in spite of robust antibody responses, suggesting that immunopathology may contribute to the lesions. Immunoblot analyses indicated that isolates are antigenically similar; thus, there may be partial cross-protection if a house finch encounters two or more strains of MG throughout the course of its lifetime. This study provides evidence that MG strains or strain variants circulating in house finch populations vary in their ability to cause disease, induce antibody responses, and persist in the host.

Patterns of connectivity in Citril Finches Serinus citrinella: sympatric wintering of allopatric breeding birds?

Capsule Individuals ringed at different localities, where previous analyses detected local genetic and morphological differentiation, overlapped in wintering areas. Aims To analyse winter site fidelity and connectivity in Citril Finches, a species with locally differentiated allopatric breeding populations, but which forms into pairs at the end of the wintering period, when these populations could be sympatric. Methods Analysis based on 238 recoveries obtained from 12 648 birds ringed at alpine localities and 2368 birds ringed at lower-elevation wintering areas in Central Catalonia. Results Citril Finches showed marked winter site fidelity. Birds ringed at different sub-alpine mountain ranges tended to winter in different river basins, but we found some overlap between these sub-populations. Birds from different localities within the same mountain range partly overlapped in wintering areas. Conclusion We found that many Citril Finch sub-populations cohabit during the winter pair formation period, which prompts the question of how Citril Finch populations can maintain local differentiation despite the ample opportunities for gene flow.

A CENTURY OF GENETIC CHANGE AND METAPOPULATION DYNAMICS IN THE GALÁPAGOS WARBLER FINCHES (CERTHIDEA)

Populations that are connected by immigrants play an important role in evolutionary and conservation biology, yet we have little direct evidence of how such metapopulations change genetically over evolutionary time. We compared historic (1894-1906) to modern (1988-2006) genetic variation in 11 populations of warbler finches at 14 microsatellite loci. Although several lines of evidence suggest that Darwin's finches may be in decline, we found that the genetic diversity of warbler finches has not generally declined, and broad-scale patterns of variation remained similar over time. Contrary to expectations, inferred population sizes have generally increased over time (6-8%) as have immigration rates (8-16%), which may reflect a recent increase in the frequency and intensity of El Niño events. Individual island populations showed significant declines (18-19%) and also substantial gains (18-20%) in allelic richness over time. Changes in genetic diversity were correlated with changes in immigration rates, but did not correspond to population size or human disturbance. These results reflect the expected stabilizing properties of whole metapopulations over time. However, the dramatic and unpredictable changes observed in individual populations during this short time interval suggests that care should be taken when monitoring individual population fragments with snapshots of genetic variation.

Rapid evolution of disease resistance is accompanied by functional changes in gene expression in a wild bird

Wild organisms are under increasing pressure to adapt rapidly to environmental changes. Predicting the impact of these changes on natural populations requires an understanding of the speed with which adaptive phenotypes can arise and spread, as well as of the underlying mechanisms. However, our understanding of these parameters is poor in natural populations. Here we use experimental and molecular approaches to investigate the recent emergence of resistance in eastern populations of North American house finches (Carpodacus mexicanus) to Mycoplasma galliseptum (MG), a severe conjunctivitis-causing bacterium. Two weeks following an experimental infection that took place in 2007, finches from eastern US populations with a 12-y history of exposure to MG harbored 33% lower MG loads in their conjunctivae than finches from western US populations with no prior exposure to MG. Using a cDNA microarray, we show that this phenotypic difference in resistance was associated with differences in splenic gene expression, with finches from the exposed populations up-regulating immune genes postinfection and those from the unexposed populations generally down-regulating them. The expression response of western US birds to experimental infection in 2007 was more similar to that of the eastern US birds studied in 2000, 7 y earlier in the epizootic, than to that of eastern birds in 2007. These results support the hypothesis that resistance has evolved by natural selection in the exposed populations over the 12 y of the epizootic. We hypothesize that host resistance arose and spread from standing genetic variation in the eastern US and highlight that natural selection can lead to rapid phenotypic evolution in populations when acting on such variation.

Using an Electronic Monitoring System to Link Offspring Provisioning and Foraging Behavior of a Wild Passerine

ABSTRACT. Although the costs of parental care are at the foundations of optimal-parental-investment theory, our understanding of the nature of the underlying costs is limited by the difficulty of measuring variation in foraging effort. We simultaneously measured parental provisioning and foraging behavior in a free-living population of Zebra Finches (Taeniopygia guttata) using an electronic monitoring system. We fitted 145 adults with a passive transponder tag and remotely recorded their visits to nest boxes and feeders continuously over a 2-month period. After validating the accuracy of this monitoring system, we studied how provisioning and foraging activities varied through time (day and breeding cycle) and influenced the benefits (food received by the offspring) and costs (interclutch interval) of parental care. The provisioning rates of wild Zebra Finches were surprisingly low, with an average of only one visit per hour throughout the day. This was significantly lower than those reported for this mod...

Correlates of male fitness in captive zebra finches - a comparison of methods to disentangle genetic and environmental effects

BackgoundIt is a common observation in evolutionary studies that larger, more ornamented or earlier breeding individuals have higher fitness, but that body size, ornamentation or breeding time does not change despite of sometimes substantial heritability for these traits. A possible explanation for this is that these traits do not causally affect fitness, but rather happen to be indirectly correlated with fitness via unmeasured non-heritable aspects of condition (e.g. undernourished offspring grow small and have low fitness as adults due to poor health). Whether this explanation applies to a specific case can be examined by decomposing the covariance between trait and fitness into its genetic and environmental components using pedigree-based animal models. We here examine different methods of doing this for a captive zebra finch population where male fitness was measured in communal aviaries in relation to three phenotypic traits (tarsus length, beak colour and song rate).ResultsOur case study illustrates how methods that regress fitness over breeding values for phenotypic traits yield biased estimates as well as anti-conservative standard errors. Hence, it is necessary to estimate the genetic and environmental covariances between trait and fitness directly from a bivariate model. This method, however, is very demanding in terms of sample sizes. In our study parameter estimates of selection gradients for tarsus were consistent with the hypothesis of environmentally induced bias (βA = 0.035 ± 0.25 (SE), βE = 0.57 ± 0.28 (SE)), yet this differences between genetic and environmental selection gradients falls short of statistical significance.ConclusionsTo examine the generality of the idea that phenotypic selection gradients for certain traits (like size) are consistently upwardly biased by environmental covariance a meta-analysis across study systems will be needed.

Mycoplasmal Conjunctivitis in House Finches (Carpodacus Mexicanus) is More Severe in Left Eyes than Right

One of the most well-studied avian diseases is the annual outbreak of Mycoplasma gallisepticum (MG) infections in house finches (Carpodacus mexicanus) in North America. This is a bacterial disease that causes conjunctivitis in one or both eyes of the host. While studying this disease in a New York finch population, researchers observed that there was a tendency for the conjunctivitis to be more prominent in the left eye of infected birds, although the small sample size of that study made it difficult to draw conclusions regarding this unusual observation. Here, this idea is tested further using a larger data set from a 4-year trapping study of house finches in Atlanta, Georgia, USA, a location with a high prevalence of MG infections. The severity of conjunctivitis in each eye of infected birds was scored on a 0–3 scale, and these data were statistically examined to identify possible side-biases in severity. Out of 254 house finches with conjunctivitis, the eye scores of all left eyes were significantly higher than right eye scores. There was no evidence for differential effects of conjunctivitis in left-bias or right-biased infections, and the left-biased pattern was similar in both sexes and in adult and young birds. These results confirm the anecdotal observation from the New York population and suggest that this is a universal phenomenon in the house finch–MG system. The significance of the finding is unknown, although the possibility exists that house finches display a degree of ‘handedness’ that causes their left sides to be exposed more frequently to potential fomites (i.e. bird feeders).

Interference from long-tailed finches constrains reproduction in the endangered Gouldian finch

1. Interspecific interference competition for nest-sites among cavity-nesting birds can have important effects on reproductive fitness and the distribution of competing species. 2. We observed interference at nest-sites in free-living populations of the endangered Gouldian finch (Erythrura gouldiae) and sympatric long-tailed finch (Poephila acuticauda), and also experimentally tested the relative strength and effect of interference at nest-sites in captive populations. 3. Levels of competitive interference at nest-sites in the wild were high for Gouldian, but not long-tailed finches, and interference frequency was inversely related to Gouldian finch reproductive success. High levels of interference conferred reduced fledging success but did not affect offspring condition. 4. Captive experiments corroborated the field data, also demonstrating fitness costs of interspecific competition, and that long-tailed finches dominated resources under standardized conditions. 5. Such asymmetrical competition dynamics are likely to constrain reproduction in Gouldian finch populations, potentially affecting recruitment and hindering the recovery of remaining populations of this endangered species.

Disentangling Ancient Interactions: A New Extinct Passerine Provides Insights on Character Displacement among Extinct and Extant Island Finches

BackgroundEvolutionary studies of insular biotas are based mainly on extant taxa, although such biotas represent artificial subsets of original faunas because of human-caused extinctions of indigenous species augmented by introduced exotic taxa. This makes it difficult to obtain a full understanding of the history of ecological interactions between extant sympatric species. Morphological bill variation of Fringilla coelebs and F. teydea (common and blue chaffinches) has been previously studied in the North Atlantic Macaronesian archipelagos. Character displacement between both species has been argued to explain bill sizes in sympatry. However, this explanation is incomplete, as similar patterns of bill size have been recorded in F. coelebs populations from islands with and without F. teydea.Methodology/Principal FindingsThe discovery of a new extinct species in Tenerife (Canary Islands), here named Carduelis aurelioi n. sp. (slender-billed greenfinch), provides the opportunity to study ancient ecological interactions among Macaronesian finches. To help understand the evolutionary histories of forest granivores in space and time, we have performed a multidisciplinary study combining: (1) morphological analyses and radiocarbon dating (11,460±60 yr BP) of the new taxon and, (2) molecular divergence among the extant finch species and populations in order to infer colonization times (1.99 and 1.09 My for F. teydea and F. coelebs respectively).Conclusion/Significance C. aurelioi, F. coelebs and F. teydea co-habited in Tenerife for at least one million years. The unique anatomical trends of the new species, namely chaffinch-like beak and modified hind and forelimbs, reveal that there was a process of divergence of resource competition traits among the three sympatric finches. The results of our study, combined with the presence of more extinct greenfinches in other Macaronesian islands with significant variation in their beak sizes, suggests that the character displacement has influenced patterns of divergence in bill size and shape on other Macaronesian islands as well.