46 results found
Matsushima W, Brink K, Schroeder J, et al., 2019, Mature sperm small-RNA profile in the sparrow: implications for transgenerational effects of age on fitness., Environ Epigenet, Vol: 5
Mammalian sperm RNA has recently received a lot of interest due to its involvement in epigenetic germline inheritance. Studies of epigenetic germline inheritance have shown that environmental exposures can induce effects in the offspring without altering the DNA sequence of germ cells. Most mechanistic studies were conducted in laboratory rodents and C.elegans while observational studies confirm the phenotypic phenomenon in wild populations of humans and other species including birds. Prominently, paternal age in house sparrows affects offspring fitness, yet the mechanism is unknown. This study provides a first reference of house sparrow sperm small RNA as an attempt to uncover their role in the transmission of the effects of paternal age on the offspring. In this small-scale pilot, we found no statistically significant differences between miRNA and tRNA fragments in aged and prime sparrow sperm. These results indicate a role of other epigenetic information carriers, such as distinct RNA classes, RNA modifications, DNA methylation and retained histones, and a clear necessity of future studies in wild populations.
Matsushima W, Brink K, Schroeder J, et al., 2019, Mature sperm small RNA profile in the sparrow: implications for transgenerational effects of age on fitness
Mammalian sperm RNA has recently received a lot of interest due to its involvement in epigenetic germline inheritance. Studies of epigenetic germline inheritance have shown that environmental exposures can induce effects in the offspring without altering the DNA sequence of germ cells. Most mechanistic studies were conducted in laboratory rodents and C. elegans while observational studies confirm the phenotypic phenomenon in wild populations of humans and other species including birds. Prominently, paternal age in house sparrows affects offspring fitness, yet the mechanism is unknown. This study provides a first reference of house sparrow sperm small RNA as an attempt to uncover their role in the transmission of the effects of paternal age on the offspring. In this small scale pilot, we found no statistically significant differences between miRNA and tRNA fragments in aged and prime sparrow sperm. These results indicate a role of other epigenetic information carriers, such as distinct RNA classes, RNA modifications, DNA methylation and retained histones, and a clear necessity of future studies in wild populations.
Schroeder J, Redfern C, Boothbu C, 2018, An evaluation of canes as management technique to reduce predation by gulls on ground nesting seabirds, Ibis, ISSN: 0019-1019
The best documented method to decrease predation of breeding seabirds by gulls are culling regimes; however, studies on the effectiveness of this method show ambiguous results. Here we tested an alternative method, using bamboo canes erected in four breeding sites of Arctic Tern Sterna paradisaea as a gull‐deterrent. Although we found fewer predation attempts in the caned areas than in the control areas, canes did not reduce the probability of predation success per attempt. This pilot study documents that the use of canes as a conservation strategy to reduce gull predation is promising, economic and simple, and is thus probably a versatile tool for conservation managers.
Sanchez-Tojar A, Nakagawa S, Sanchez-Fortun M, et al., 2018, Meta-analysis challenges a textbook example of status signalling and demonstrates publication bias, eLife, Vol: 7, ISSN: 2050-084X
The status signalling hypothesis aims to explain within-species variation inornamentation by suggesting that some ornaments signal dominance status. Here, we usemultilevel meta-analytic models to challenge the textbook example of this hypothesis, the black bibof male house sparrows (Passer domesticus). We conducted a systematic review, and obtainedprimary data from published and unpublished studies to test whether dominance rank is positivelyassociated with bib size across studies. Contrary to previous studies, the overall effect size (i.e.meta-analytic mean) was small and uncertain. Furthermore, we found several biases in the literaturethat further question the support available for the status signalling hypothesis. We discuss severalexplanations including pleiotropic, population- and context-dependent effects. Our findings call forreconsidering this established textbook example in evolutionary and behavioural ecology, andshould stimulate renewed interest in understanding within-species variation in ornamental traits.
Edwards HA, Schroeder J, Dugdale HL, 2018, Gender differences in authorships are not associated with publication bias in an evolutionary journal, PLoS ONE, Vol: 13, ISSN: 1932-6203
The loss of talented women from senior academic positions has partly resulted from a lower number of published papers and the accompanying reduced visibility of female compared to male scientists. The reasons for these gender-differences in authorship is unclear. One potential reason is a bias in the editorial and review process of scientific journals. We investigated whether patterns of authorship and editorial outcome were biased according to gender and geographic location in the Journal of Evolutionary Biology. Such potential bias may contribute to inequality in the field. We found patterns of gender differences in authorship, but this was unrelated to the editorial decision of whether to publish the manuscript. Female first-authors (the lead role) were six times less likely to be named as the corresponding author than male first-authors, and female first-authors were more likely to be displaced as corresponding authors by female co-authors than were male first-authors. We found an under-representation of female first- and last-authors compared to baseline populations of members of the European Society for Evolutionary Biology (which publishes the Journal of Evolutionary Biology) and of Evolutionary Biology faculty at the world top-10 universities for the Life Sciences. Also, manuscripts from Asia were five times more likely to be rejected on the final decision, independent of gender. Overall our results suggest that the peer review processes we investigated at the Journal of Evolutionary Biology are predominately gender-neutral, but not neutral to geographic location. Editorial gender-bias is thus unlikely to be a contributing factor to differences in authorship in this journal.
Girndt A, Chng CWT, Burke T, et al., 2018, Male age is associated with extra-pair paternity, but not with extra-pair mating behaviour, Publisher: Cold Spring Harbor Laboratory
<jats:p>Extra-pair paternity is the result of copulation between a female and a male other than her social partner. In socially monogamous birds, old males are most likely to sire extra-pair offspring. The male manipulation and female choice hypotheses predict that age-specific male mating behaviour could explain this old-over-young male advantage. These hypotheses have been difficult to test because copulations and the individuals involved are hard to observe. Here, we studied the mating behaviour and pairing contexts of captive house sparrows, Passer domesticus. Our set-up mimicked the complex social environment experienced by wild house sparrows. We found that middle-aged males, that would be considered old in natural populations, gained most extra-pair paternity. However, both female solicitation behaviour and subsequent extra-pair matings were unrelated to male age. Further, copulations were more likely when solicited by females than those initiated by males (i.e. unsolicited copulations), and unsolicited within-pair copulations were more common than unsolicited extra-pair copulations. To conclude, our results did not support either hypotheses regarding age-specific male mating behaviour. Instead, female choice, independent of male age, governed copulation success, especially in an extra-pair context and post-copulatory mechanisms might determine why older males sire more extra-pair offspring.</jats:p>
Girndt A, Change WT, Burke T, et al., 2018, Male age is associated with extra-pair paternity, but not with extra-pair mating behaviour, Scientific Reports, Vol: 8, ISSN: 2045-2322
Extra-pair paternity is the result of copulation between a female and a male other than her social partner. In socially monogamous birds, old males are most likely to sire extra-pair offspring. The male manipulation and female choice hypotheses predict that age-specific male mating behaviour could explain this old-over-young male advantage. These hypotheses have been difficult to test because copulations and the individuals involved are hard to observe. Here, we studied the mating behaviour and pairing contexts of captive house sparrows, Passer domesticus. Our set-up mimicked the complex social environment experienced by wild house sparrows. We found that middle-aged males, which would be considered old in natural populations, gained most extra-pair paternity. However, both, female solicitation behaviour and subsequent extra-pair matings were not associated with male age. Further, copulations were more likely when solicited by females than when initiated by males (i.e. unsolicited copulations). Male initiated within-pair copulations were more common than male initiated extra-pair copulations. To conclude, our results did not support either hypothesis regarding age-specific male mating behaviour. Instead, female choice, independent of male age, governed copulation success, especially in an extra-pair context. Post-copulatory mechanisms might determine why older males sire more extra-pair offspring.
Sanchez-Tojar A, Schroeder J, Farine DR, 2018, A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty, JOURNAL OF ANIMAL ECOLOGY, Vol: 87, Pages: 594-608, ISSN: 0021-8790
Winney IS, Schroeder J, Nakagawa S, et al., 2018, Heritability and social brood effects on personality in juvenile and adult life-history stages in a wild passerine, JOURNAL OF EVOLUTIONARY BIOLOGY, Vol: 31, Pages: 75-87, ISSN: 1010-061X
Baugh AT, Senft RA, Firke M, et al., 2017, Risk-averse personalities have a systemically potentiated neuroendocrine stress axis: A multilevel experiment in Parus major, Hormones and Behavior, Vol: 93, Pages: 99-108, ISSN: 0018-506X
Hormonal pleiotropy-the simultaneous influence of a single hormone on multiple traits-has been hypothesized as an important mechanism underlying personality, and circulating glucocorticoids are central to this idea. A major gap in our understanding is the neural basis for this link. Here we examine the stability and structure of behavioral, endocrine and neuroendocrine traits in a population of songbirds (Parus major). Upon identifying stable and covarying behavioral and endocrine traits, we test the hypothesis that risk-averse personalities exhibit a neuroendocrine stress axis that is systemically potentiated-characterized by stronger glucocorticoid reactivity and weaker negative feedback. We show high among-individual variation and covariation (i.e. personality) in risk-taking behaviors and demonstrate that four aspects of glucocorticoid physiology (baseline, stress response, negative feedback strength and adrenal sensitivity) are also repeatable and covary. Further, we establish that high expression of mineralocorticoid and low expression of glucocorticoid receptor in the brain are linked with systemically elevated plasma glucocorticoid levels and more risk-averse personalities. Our findings support the hypothesis that steroid hormones can exert pleiotropic effects that organize behavioral phenotypes and provide novel evidence that neuroendocrine factors robustly explain a large fraction of endocrine and personality variation.
Girndt A, Cockburn G, Sánchez-Tójar A, et al., 2017, Method matters: experimental evidence for shorter avian sperm in faecal compared to abdominal massage samples, PLOS One, Vol: 12, ISSN: 1932-6203
Birds are model organisms in sperm biology. Previous work in zebra finches, suggested that sperm sampled from males' faeces and ejaculates do not differ in size. Here, we tested this assumption in a captive population of house sparrows, Passer domesticus. We compared sperm length in samples from three collection techniques: female dummy, faecal and abdominal massage samples. We found that sperm were significantly shorter in faecal than abdominal massage samples, which was explained by shorter heads and midpieces, but not flagella. This result might indicate that faecal sampled sperm could be less mature than sperm collected by abdominal massage. The female dummy method resulted in an insufficient number of experimental ejaculates because most males ignored it. In light of these results, we recommend using abdominal massage as a preferred method for avian sperm sampling. Where avian sperm cannot be collected by abdominal massage alone, we advise controlling for sperm sampling protocol statistically.
Schroeder J, Masero JA, Abad-Gomez JM, et al., 2017, Wetland salinity induces sex-dependent carry-over effects on the individual performance of a long-distance migrant, Scientific Reports, Vol: 7, ISSN: 2045-2322
Salinization is having a major impact on wetlands and its biota worldwide. Specifically, many migratory animals that rely on wetlands are increasingly exposed to elevated salinity on their nonbreeding grounds. Experimental evidence suggests that physiological challenges associated with increasing salinity may disrupt self-maintenance processes in these species. Nonetheless, the potential role of salinity as a driver of ecological carry-over effects remains unstudied. Here, we investigated the extent to which the use of saline wetlands during winter – inferred from feather stable isotope values – induces residual effects that carry over and influence physiological traits relevant to fitness in black-tailed godwits Limosa limosa limosa on their northward migration. Overwintering males and females were segregated by wetland salinity in West Africa, with females mostly occupying freshwater wetlands. The use of these wetlands along a gradient of salinities was associated with differences in immune responsiveness to phytohaemagglutinin and sized-corrected body mass in godwits staging in southern Europe during northward migration – 3,000 km from the nonbreeding grounds – but in males only. These findings provide a window onto the processes by which wetland salinity can induce carry-over effects and can help predict how migratory species should respond to future climate-induced increases in salinity.
Parau LG, Kingma SA, Weigl SE, et al., 2017, Dynamics in numbers of group-roosting individuals in relation to pair-sleeping occurrence and onset of egg-laying in European Bee-eaters Merops apiaster, Journal of Ornithology, Vol: 158, Pages: 1119-1122, ISSN: 0021-8375
Sleeping in the nest at the beginning of the breeding season is common for birds nesting in cavities. Here, we report evidence that European Bee-eaters Merops apiaster sleep in pairs in the nesting burrow. In 3.2% of the nest checks, we found two individuals sleeping together. This behaviour ceased once hatching started. A decrease in the number of birds at a communal roost coincided with the incidences of pair-sleeping and initiation of egg-laying. Thus, checking the burrows of European Bee-eaters at the beginning of the breeding season increases the chance of observing pair-sleeping.
Hsu Y-H, Simons MJP, Schroeder J, et al., 2017, Age-dependent trajectories differ between within-pair and extra-pair paternity success, Journal of Evolutionary Biology, Vol: 30, Pages: 951-959, ISSN: 1010-061X
Reproductive success is associated with age in many taxa, increasing in early life followed by reproductive senescence. In socially monogamous but genetically polygamous species, this generates the interesting possibility of differential trajectories of within-pair and extra-pair siring success with age in males. We investigate these relationships simultaneously using within-individual analyses with 13 years of data from an insular house sparrow (Passer domesticus) population. As expected, we found that both within- and extra-pair paternity success increased with age, followed by a senescence-like decline. However, the age trajectories of within- and extra-pair paternity successes differed significantly, with the extra-pair paternity success increasing faster, although not significantly, in early life, and showing a delayed decline by 1.5 years on average later in life compared to within-pair paternity success. These different trajectories indicate that the two alternative mating tactics should have age-dependent pay-offs. Males may partition their reproductive effort between within- and extra-pair matings depending on their current age to reap the maximal combined benefit from both strategies. The interplay between these mating strategies and age-specific mortality may explain the variation in rates of extra-pair paternity observed within and between species.
Sanchez-Tojar A, Winney I, Girndt A, et al., 2016, Winter territory prospecting is associated with life-history stage but not activity in a passerine, Journal of Avian Biology, Vol: 48, Pages: 407-416, ISSN: 1600-048X
Finding a high quality territory is essential for many animals to reproduce successfully. Despite its importance for fitness, we know little about the process of territory prospecting in wild birds, and whether individual traits and behaviours, such as personality, co-vary with territory prospecting. Here, we use long-term data from a wild, insular house sparrow Passer domesticus population to test three hypotheses about territory fidelity and prospecting: 1) house sparrows show high territory fidelity between years and also during winter. 2) Individuals will prospect for a breeding territory during their first winter whereas older, more experienced individuals will keep a territory from previous years and will, therefore, show no or reduced winter territory prospecting. 3) More active behavioural types will prospect more than less active behavioural types. We use data from four winters from automatically, daily recorded nest-box visits of 188 birds of known age. The number of nest-boxes that each individual visited within each winter was used as a proxy of winter territory prospecting. We show that house sparrows visit multiple nest-boxes during their first winter, whereas older individuals keep territories year-round and, potentially because of this, indeed show reduced winter territory prospecting. Activity was not associated with the number of nest-boxes visited. Further research is needed to investigate whether time of territory and mate acquisition differs among individuals and the possible effect on lifetime fitness.
Schroeder J, Yu-Hsun, Winney I, et al., 2016, Predictably philandering females prompt poor paternal provisioning, American Naturalist, Vol: 188, Pages: 219-230, ISSN: 1537-5323
One predicted cost of female infidelity in socially monogamous species is that cuckolded males should provide less parental care. This relationship is robust across species, but evidence is ambiguous within species. We do not know whether individual males reduce their care when paired with cheating females compared with when paired with faithful females (within-male adjustment) or, alternatively, if the males that pair with cheating females are the same males that provide less parental care in general (between-male effect). Our exceptionally extensive long-term data set of repeated observations of a wild passerine allows us to disentangle paternal care adjustment within males—within pairs and between males—while accounting for environmental variables. We found a within-male adjustment of paternal provisioning, but not incubation effort, relative to the cuckoldry in their nest. This effect was mainly driven by females differing consistently in their fidelity. There was no evidence that this within-male adjustment also took place across broods with the same female, and we found no between-male effect. Interestingly, males that gained more extrapair paternity provided less care. Data from a cross-foster experiment suggested that males did not use kin recognition to assess paternity. Our results provide insight into the role of individual variation in parental care and mating systems.
Schroeder J, Dugdale HL, Ghaniya B, et al., 2016, A multiplex set for microsatellite typing and sexing of the European bee-eater (Merops apiaster), European Journal of Wildlife Research, Vol: 62, Pages: 501-509, ISSN: 1612-4642
Microsatellite loci are widely used in ecological and evolutionary studies to assess inbreeding, genetic parentage and population structure. Such loci are often optimised in multiplexes to allow for economical and efficient use. Here, we tested 11 microsatellite loci designed for use in European bee-eaters (Merops apiaster), along with 31 loci isolated in other species, for their utility in European bee-eaters sampled on Susak Island, Croatia. Of these 42 loci, 20 were polymorphic in 38 individuals. These polymorphic loci were further assessed in a sub-set of 23 adults, excluding close relatives, and exhibited between three and 13 alleles each. All loci were autosomal, as indicated by the presence of heterozygotes in both males and females. One of the polymorphic loci exhibited low heterozygosity, three loci deviated from Hardy-Weinberg equilibrium and three pairs of loci displayed linkage disequilibrium. The remaining selected eight cross-species loci and seven loci isolated in European bee-eaters were combined with two sex-typing markers and optimised in five multiplexes. A combination of 15 autosomal loci of varying degrees of polymorphism makes this multiplex set particularly suitable for both parentage and spatial genetic analyses. This multiplex set therefore provides a useful toolkit for studying kin selection and population genetics in the cooperatively breeding European bee-eater and, potentially, in other closely related species.
Schroeder J, Parau, Stubbe D, et al., 2016, Rose-ringed parakeet Psittacula krameri populations and numbers in Europe: a complete overview, Open Ornithology Journal, Vol: 9, ISSN: 1874-4532
Purpose:Alien species are considered one of the major causes contributing to the current loss of biodiversity. Over the past few decades, a large and increasing number of alien species have become invasive in many parts of the world. Their impacts range from competition for resources with native species to damage of urban infrastructure. In Europe, over a thousand alien species are now established, of which 74 are birds. Among 12 established alien parrot species in Europe,Introduction:The Rose-ringed Parakeet (RRP) Psittacula krameri (Scopoli, 1769) is the most abundant and widespread. Since the 1960's, RRPshave established more than 100 wild populations in several European countries. For Western Europe, long-term demographic data indicate the species has grown considerably in number, although some populations have failed to persist.Data:Is scarce and dispersed for countries in Central, Eastern and Northern Europe. Therefore, here we present detailed demographic data of RRP for 90 populations in 10 European countries. Furthermore, we present information on the status of the species in another 27 European countries, for which previously no data were published.Conclusion:Our synthesis reveals a positive demographic trend across the continent, although locally, some populations appear to have reached carrying capacity.
Simons MJ, Winney I, Nakagawa S, et al., 2015, Limited catching bias in a wild population of birds with near-complete census information., Ecology and Evolution, Vol: 5, Pages: 3500-3506, ISSN: 2045-7758
Animal research often relies on catching wild animals; however, individuals may have different trappability, and this can generate bias. We studied bias in mist netting, the main method for catching wild birds. The unusually high resighting rate in our study population-house sparrows (Passer domesticus) on Lundy Island (England)-allowed us to obtain accurate estimates of the population size. This unique situation enabled us to test for catching bias in mist netting using deviations from the expected Poisson distribution. There was no evidence that a fraction of the birds in the population consistently remained uncaught. However, we detected a different bias: More birds than expected were captured only once within a year. This bias probably resulted from a mixture of fieldworkers sometimes ignoring rapid recaptures and birds becoming net shy after their first capture. We had sufficient statistical power with the available data to detect a substantial uncaught fraction. Therefore, our data are probably unbiased toward catching specific individuals from our population. Our analyses demonstrate that intensively monitored natural insular populations, in which population size can be estimated precisely, provide the potential to address important unanswered questions without concerns about a fraction of the population remaining uncaught. Our approach can help researchers to test for catching bias in closely monitored wild populations for which reliable estimates of population size and dispersal are available.
Nakagawa S, Schroeder J, Burke T, 2015, Sugar-free extrapair mating: a comment on Arct et al., BEHAVIORAL ECOLOGY, Vol: 26, Pages: 971-972, ISSN: 1045-2249
Winney I, Nakagawa S, Hsu Y-H, et al., 2015, Troubleshooting the potential pitfalls of cross-fostering, METHODS IN ECOLOGY AND EVOLUTION, Vol: 6, Pages: 584-592, ISSN: 2041-210X
Hsu Y-H, Schroeder J, Winney I, et al., 2015, Are extra-pair males different from cuckolded males? A case study and a meta-analytic examination, MOLECULAR ECOLOGY, Vol: 24, Pages: 1558-1571, ISSN: 0962-1083
Schroeder J, Nakagawa S, Rees M, et al., 2015, Reduced fitness in progeny from old parents in a natural population., Proceedings of the National Academy of Sciences of the United States of America, Vol: 112, Pages: 4021-4025, ISSN: 1091-6490
A nongenetic, transgenerational effect of parental age on offspring fitness has been described in many taxa in the laboratory. Such a transgenerational fitness effect will have important influences on population dynamics, population age structure, and the evolution of aging and lifespan. However, effects of parental age on offspring lifetime fitness have never been demonstrated in a natural population. We show that parental age has sex-specific negative effects on lifetime fitness, using data from a pedigreed insular population of wild house sparrows. Birds whose parents were older produced fewer recruits annually than birds with younger parents, and the reduced number of recruits translated into a lifetime fitness difference. Using a long-term cross-fostering experiment, we demonstrate that this parental age effect is unlikely to be the result of changes in the environment but that it potentially is epigenetically inherited. Our study reveals the hidden consequences of late-life reproduction that persist into the next generation.
Karlsson M, Schroeder J, Nakagawa S, et al., 2015, House sparrow Passer domesticus survival is not associated with MHC-I diversity, but possibly with specific MHC-I alleles, JOURNAL OF AVIAN BIOLOGY, Vol: 46, Pages: 167-174, ISSN: 0908-8857
Hsu Y-H, Schroeder J, Winney I, et al., 2014, COSTLY INFIDELITY: LOW LIFETIME FITNESS OF EXTRA-PAIR OFFSPRING IN A PASSERINE BIRD, EVOLUTION, Vol: 68, Pages: 2873-2884, ISSN: 0014-3820
Westneat DF, Bokony V, Burke T, et al., 2014, Multiple aspects of plasticity in clutch size vary among populations of a globally distributed songbird, JOURNAL OF ANIMAL ECOLOGY, Vol: 83, Pages: 876-887, ISSN: 0021-8790
Schroeder J, Dugdale HL, Radersma R, et al., 2013, Fewer invited talks by women in evolutionary biology symposia, Journal of Evolutionary Biology, Vol: 26, Pages: 2063-2069, ISSN: 1420-9101
Lower visibility of female scientists, compared to male scientists, is a potential reason for the under-representation of women among senior academic ranks. Visibility in the scientific community stems partly from presenting research as an invited speaker at organized meetings. We analysed the sex ratio of presenters at the European Society for Evolutionary Biology (ESEB) Congress 2011, where all abstract submissions were accepted for presentation. Women were under-represented among invited speakers at symposia (15% women) compared to all presenters (46%), regular oral presenters (41%) and plenary speakers (25%). At the ESEB congresses in 2001-2011, 9-23% of invited speakers were women. This under-representation of women is partly attributable to a larger proportion of women, than men, declining invitations: in 2011, 50% of women declined an invitation to speak compared to 26% of men. We expect invited speakers to be scientists from top ranked institutions or authors of recent papers in high-impact journals. Considering all invited speakers (including declined invitations), 23% were women. This was lower than the baseline sex ratios of early-mid career stage scientists, but was similar to senior scientists and authors that have published in high-impact journals. High-quality science by women therefore has low exposure at international meetings, which will constrain Evolutionary Biology from reaching its full potential. We wish to highlight the wider implications of turning down invitations to speak, and encourage conference organizers to implement steps to increase acceptance rates of invited talks.
Schroeder J, Cleasby I, Dugdale HL, et al., 2013, Social and genetic benefits of parental investment suggest sex differences in selection pressures, JOURNAL OF AVIAN BIOLOGY, Vol: 44, Pages: 133-140, ISSN: 0908-8857
Edwards HA, Winney IS, Schroeder J, et al., 2013, Do rapid assays predict repeatability in labile (behavioural) traits? A reply to Biro, ANIMAL BEHAVIOUR, Vol: 85, Pages: E1-E3, ISSN: 0003-3472
Schroeder J, Nakagawa S, Cleasby IR, et al., 2012, Passerine birds breeding under chronic noise experience reduced fitness, PLOS One, Vol: 7, ISSN: 1932-6203
BACKGROUND: Fitness in birds has been shown to be negatively associated with anthropogenic noise, but the underlying mechanisms remain obscure. It is however crucial to understand the mechanisms of how urban noise impinges on fitness to obtain a better understanding of the role of chronic noise in urban ecology. Here, we examine three hypotheses on how noise might reduce reproductive output in passerine birds: (H1) by impairing mate choice, (H2) by reducing territory quality and (H3) by impeding chick development. METHODOLOGY/PRINCIPAL FINDINGS: We used long-term data from an island population of house sparrows, Passer domesticus, in which we can precisely estimate fitness. We found that nests in an area affected by the noise from large generators produced fewer young, of lower body mass, and fewer recruits, even when we corrected statistically for parental genetic quality using a cross-fostering set-up, supporting H3. Also, individual females provided their young with food less often when they bred in the noisy area compared to breeding attempts by the same females elsewhere. Furthermore, we show that females reacted flexibly to increased noise levels by adjusting their provisioning rate in the short term, which suggests that noise may be a causal factor that reduces reproductive output. We rejected H1 and H2 because nestbox occupancy, parental body mass, age and reproductive investment did not differ significantly between noisy and quiet areas. CONCLUSIONS/SIGNIFICANCE: OUR RESULTS SUGGEST A PREVIOUSLY UNDESCRIBED MECHANISM TO EXPLAIN HOW ENVIRONMENTAL NOISE CAN REDUCE FITNESS IN PASSERINE BIRDS: by acoustically masking parent-offspring communication. More importantly, using a cross-fostering set-up, our results demonstrate that birds breeding in a noisy environment experience significant fitness costs. Chronic noise is omnipresent around human habitation and may produces similar fitness consequences in a wide range of urban bird species.
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