Julia Schroeder

Passerine birds breeding under chronic noise experience reduced fitness

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.

Fewer invited talks by women in evolutionary biology symposia

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.

Repeatable timing of northward departure, arrival and breeding in Black-tailed Godwits Limosa l. limosa, but no domino effects

When early breeding is advantageous, migrants underway to the breeding areas may be time stressed. The timing of sequential events such as migration and breeding is expected to be correlated because of a “domino effect”, and would be of particular biological importance if timings are repeatable within individuals between years. We studied a colour-marked population of Black-tailed Godwits Limosa l. limosa both on staging areas in Portugal and on breeding areas in The Netherlands. For each individual, we measured the timing of the staging period, the arrival date on the breeding area and the egg laying date. We measured average egg volume as a measure of reproductive investment. The date of departure from the staging areas, the arrival date on the breeding areas, and the egg laying date were repeatable among years in individual Black-tailed Godwits. The arrival dates of paired males and females and the average annual male and female arrival dates were correlated. The dates of departure from Portugal, arrival in The Netherlands, and egg laying were not correlated. Earlier clutches had larger eggs than late clutches. If the length of the individually available pre-laying period is accounted for, early arriving birds spent more time on the breeding grounds before laying than late arriving birds. The repeatability of the itineraries and the correlation between arrival timing of males and females are consistent with observations in other migrants. Despite evidence for early breeding being advantageous, we found no evidence of a “domino effect”.ZusammenfassungLangstreckenzieher stehen unter starkem Zeitdruck wenn ein früher Brutzeitpunkt vorteilhaft ist. Es wird angenommen, dass der Zeitpunkt von Abflug, Ankunft und Eiablage von individuellen Vögeln wiederholbar zwischen den Jahren ist. Deshalb kann man erwarten, dass die Zeitpunkte dieser sequentiellen Ereignisse miteinander korrelieren: der “Dominoeffekt”. We untersuchten eine mit Farbringen markierte Uferschnepfen Population in den Rastgebieten in Portugal und im Brutgebiet in den Niederlanden. Wir wissen für jedes Individuum sowohl den Zeitraum des Aufenthalts im Rastgebiet, den Ankuftszeitpunkt im Brutgebiet, und das Eiablagedatum. Wir verwandten das durchschnittlichen Eivolumen, welches mit dem Bruterfolg korreliert, als Indikation für reproduktive Investition. Innerhalb individueller Vögel waren sowohl Abflugzeitpunkt aus den Rastgebieten, Ankunft im Brutgebiet und Eiablagedatum wiederholbar zwischen den Jahren. Die Ankunftszeitpunkte von später verpaarten Männchen und Weibchen, sowie die durchschnittlichen jährlichen Ankunftszeitpunkte beider Geschlechter waren miteinander korreliert. Abflugszeitpunkt aus den Rastgebieten, Ankunftszeitpunkt im Brutgebiet und Eiablagedatum waren jedoch nicht miteinander korreliert. Frühe Gelege enthielten größere Eier als späte Gelege. Früh ankommende Vögel hielten sich länger im Brutgebiet auf als spät ankommende Vögel, selbst wenn wir für die Dauer des Aufenthaltes korrigierten. Die Wiederholbarkeit des Zugzeitplans und die Korrelation zwischen den Geschlechtern sind im Einklang mit Beobachtungen an anderen Zugvogelarten. Trotz des offensichtlichen selektiven Vorteils eines frühen Eiablagedatums fanden wir keine Hinweise auf einen Dominoeffekt.

Reduced fitness in progeny from old parents in a natural population.

Significance As parents age, gamete quality declines. If this decline affects the next generation, it could influence the evolution of longevity. Older parents often produce offspring of low fitness in the laboratory. Our long-term data from a natural bird population shows, for the first time to our knowledge, a transgenerational reduction in fitness of the next generation associated with parental age. We use a 10-year cross-fostering experiment to exclude environmental explanations. Our results challenge the currently favored hypothesis in evolutionary biology and behavioral ecology that old age signals high quality in mating partners. Our results imply a substantial cost of reproducing with older, rather than younger, partners. The results inform increasing concern about delayed reproduction in medicine, sociology, and conservation biology. 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.

Microsatellite resources for Passeridae species: a predicted microsatellite map of the house sparrow Passer domesticus

We identified microsatellite sequences of potential utility in the house sparrow (Passer domesticus) and assigned their predicted genome locations. These sequences included newly isolated house sparrow loci, which we fully characterized. Many of the newly isolated loci were polymorphic in two other species of Passeridae: Berthelot’s pipit Anthus berthelotii and zebra finch Taeniopygia guttata. In total, we identified 179 microsatellite markers that were either isolated directly from, or are of known utility in, the house sparrow. Sixty‐seven of these markers were designed from unique sequences that we isolated from a house sparrow genomic library. These new markers were combined with 36 house sparrow markers isolated by other studies and 76 markers isolated from other passerine species but known to be polymorphic in the house sparrow. We utilized sequence homology to assign chromosomal locations for these loci in the assembled zebra finch genome. One hundred and thirty‐four loci were assigned to 25 different autosomes and eight loci to the Z chromosome. Examination of the genotypes of known‐sex house sparrows for 37 of the new loci revealed a W‐linked locus and an additional Z‐linked locus. Locus Pdoμ2, previously reported as autosomal, was found to be Z‐linked. These loci enable the creation of powerful and cost‐effective house sparrow multiplex primer sets for population and parentage studies. They can be used to create a house sparrow linkage map and will aid the identification of quantitative trait loci in passerine species.

Are extra-pair males different from cuckolded males? A case study and a meta-analytic examination

Traditional models for female extra‐pair matings assume that females benefit indirectly from extra‐pair mating behaviour. Under these so‐called adaptive models, extra‐pair males are hypothesized to have more compatible genotypes, larger body size, exaggerated ornaments or to be older than cuckolded males. Alternatively, (‘nonadaptive’) models that consider female extra‐pair matings to be a by‐product posit that female extra‐pair mating can be maintained even if there is no benefit to females. This could happen if, for example, males gained fitness benefits from extra‐pair mating, while female and male extra‐pair mating behaviours were genetically correlated. Extra‐pair males are also expected to be older and larger if this improves their ability to convince or coerce females to mate. We investigated whether a females extra‐pair mates differed from her cuckolded mate in both genetic and phenotypic traits by analysing data from an insular house sparrow population. We found that extra‐pair males were older than cuckolded males, consistent with both models. However, in contrast to the expectations from from adaptive models, extra‐pair and cuckolded males were of similar genetic relatedness, and hence expected compatibility, with the female, and had comparable body size and secondary sexual traits. We also updated previous meta‐analyses examining differences between extra‐pair and cuckolded males. The meta‐analytic results matched results from our house sparrow case study. Although we cannot completely exclude indirect benefits for females, nonadaptive models may better explain female extra‐pair matings. These neglected alternative models deserve more research attention, and this should improve our understanding of the evolution of mating systems.

Reproductive timing and investment in relation to spring warming and advancing agricultural schedules

AbstractAdvances in mowing schedules have led to early and rapid declines in the seasonal food availability for, and survival rates of, chicks of grassland-breeding waders. Concurrently, increased levels of soil fertilization may have improved food abundance for adults. These developments are assumed to have resulted in an advancement of laying during 1930–1976 in several meadowbird species, including Black-tailed Godwits. Despite an apparent selective advantage of early breeding, after 1976 Godwits stopped advancing their laying dates. We have analyzed the timing of breeding and reproductive investment in Dutch Black-tailed Godwits relative to recent changes in agricultural practices and climate during 1976–2007. Early and late spring temperatures and precipitation in March were used as indicators for the timing of fertilizer application and mowing, and also as qualitative measures of relative food availability for adults and chicks. When precipitation was higher in March, Black-tailed Godwits laid earlier. Following warmer winters, the earliest females laid larger eggs, which hatched heavier chicks with a higher survival probability. We suggest that the positive effect of an increasing March precipitation on invertebrate abundance may be constrained by the current policy of rigid control of the water table. This policy prevents Godwits from further advancing laying dates, which would increase their chick’s survival prospects under increasingly early mowing schedules. Policy-makers should, next to delaying mowing schedules, also consider reduced draining in early spring as a tool to help stop the population decline of the Black-tailed Godwit.ZusammenfassungBrutzeitpunkt und Reproduktion von Uferschnepfen in Bezug auf Veränderungen landschaftlicher Aktivitäten und Klimaerwärmung Immer frühere Mahdzeitpunkte führen zu einer immer früheren und schnellen Verringerung der saisonalen Nahrungsverfügbarkeit, und damit auch einer starken Abnahme der Überlebenschancen von Wiesenvogelküken. Im Gegensatz dazu hat die zeitgleiche zunehmende Düngung von Grasland sehr wahrscheinlich die Nahrungsgrundlage für adulte Wiesenvögel verbessert. Dies hatte zur Folge dass gleich mehrere Arten von Wiesevögeln einschließlich der Uferschnepfe zwischen 1930 und 1976 ihre Eiablage immer früher tätigten. Überraschenderweise, und obwohl eine früherer Eiablagezeitpunkt anscheinend einen Selektionsvorteil verschafft, stellten Uferschnepfen das Verfrühen der Eiablage nach 1976 ein. Hier präsentieren wir eine Analyse des Zeitpunktes der Eiablage und der Investition in die Reproduktion von niederländischen Uferschnepfen vor dem Hintergrund der rezenten Veränderungen landwirtschaftlicher Aktivitäten und des Klimas im Zeitraum von 1976–2007. Wir verwenden die mittleren Temperaturen während des frühen und späten Frühjahres sowie die Niederschlagssumme im März als Indikatoren für respektive den Zeitpunkt der Düngung, der Mahd und als qualitatives Maß des relativen Nahrungsangebot für adulte Uferschnepfen und Jungtiere. In Jahren mit feuchterem März legten Uferschnepfen ihre Eier früher. Nach wärmeren Wintern legten frühe Weibchen größere Eier, aus welchen Kücken in besserer Kondition schlüpften, welche eine bessere Überlebenswahrscheinlichkeit hatten. Unsere Resultate suggerieren, dass der positive Effekt, den die Klimaänderung auf den Niederschlag im Frühjahr, und damit auch auf die Nahrungsverfügbarkeit für adulte Uferschnepfen hat, durch die starke Kontrolle des Grundwasserspiegels zunichte gemacht wird. Dies verhindert, dass Uferschnepfen früher legen können, was die Überlebenschancen der Kücken unter immer früheren Mahdterminen deutlich verringert.

Maternal effects and heritability of annual productivity

Within‐individual consistency and among‐individual heterogeneity in fitness are prerequisites for selection to take place. Within‐individual variation in productivity between years, however, can vary considerably, especially when organisms become older and more experienced. We examine individual consistency in annual productivity, the covariation between survival and annual productivity, and the sources of variation in annual productivity, while accounting for advancing age, to test the individual‐quality and resource‐allocation life‐history theory hypotheses. We use long‐term data from a pedigreed, wild population of house sparrows. Within‐individual annual productivity first increased and later decreased with age, but there were no selective mortality due to individual quality and no correlation between lifespan and productivity. Individuals were consistent in their annual productivity (C = 0.49). Narrow‐sense heritability was low (h2 = 0.09), but maternal effects explained much of the variation (M = 0.33). Such effects can influence evolutionary processes and are of major importance for our understanding of how variation in fitness can be maintained.

Costly infidelity: Low lifetime fitness of extra-pair offspring in a passerine bird

Extra‐pair copulation (EPC) is widespread in socially monogamous species, but its evolutionary benefits remain controversial. Indirect genetic benefit hypotheses postulate that females engage in EPC to produce higher quality extra‐pair offspring (EPO) than within‐pair offspring (WPO). In contrast, the sexual conflict hypothesis posits that EPC is beneficial to males but not to females. Thus, under the sexual conflict hypothesis, EPO are predicted to be no fitter than WPO. We tested these two hypotheses in a 12‐year dataset with complete life‐history and pedigree information from an isolated island population of house sparrows (Passer domesticus). We compared fitness components of EPO and two types of WPO: (1) WPO from genetically polyandrous “unfaithful” mothers, and (2) WPO from genetically monogamous mothers. We found that all three groups of offspring had similar probabilities of hatching and nestling survival. Unexpectedly, EPO had the lowest probability of recruiting into the breeding population and the lowest lifetime reproductive output. Our results indicate that EPO incurred indirect genetic costs, rather than benefits, which is contrary to indirect benefit models. Importantly, the indirect costs we observed are also underappreciated in current sexual conflict models. Our results call for improved theoretical frameworks that incorporate indirect costs by extending current sexual conflict models.

Phenology, Stopover Dynamics and Population Size of Migrating Black-Tailed Godwits Limosa Limosa Limosa in Portuguese Rice Plantations

Between 2005/06 and 2008/09 we studied Black-tailed Godwits Limosa I. limosa staging in the rice fields surrounding the Tejo and Sado estuaries, Portugal. Godwits were counted weekly and flocks were scanned for colour-ringed individuals. We analysed phenology, dynamics of the stopover, and estimated the size of the Portuguese staging population as well as the total western limosa population, Godwits started arriving in January. Numbers peaked in the second half of February, after which they quickly departed from the area. Comparison with previous records suggested that numbers have decreased since the early 1990s, and that godwits currently peak later than some 15 years ago. Individual staging durations averaged 22.6 days in 2007 and 25.3 days in 2009, and increased towards the end of the staging period. We estimated that a total 59 200 birds used the area in 2007 and 53 100 in 2009. Using estimates for the proportion of colour-ringed birds in the flocks, we estimated the population size of the western part of the L. l. limosa population at 133 151–140 722 birds. This is higher than previous estimates based on inventories of the breeding population, but accounts for the non-breeding segment of the population. Thus, we estimate that 38–44% of the NW European Black-tailed Godwit population stage in Portugal. It is argued that processes in Iberia are not likely to have contributed to the population decline as the area for rice cultivation has increased. Nevertheless, as godwits staging in Iberia are totally dependent on human-made habitats, changes in rice farming practices could have great impact on the total population size.