Tibor Szép

Ecological conditions during winter affect sexual selection and breeding in a migratory bird.

Populations of migratory birds have undergone marked declines, although the causes and mechanisms remain unknown. Because environmental effects on population dynamics are mediated by the effects of ecological factors on individuals, understanding changes in individual phenotypes in response to ecological conditions is key to understanding population trends. We show that breeding individuals of a declining population of trans–Saharan migratory barn swallows, Hirundo rustica, were affected by environmental conditions, as estimated from the normalized difference vegetation index (NDVI), reflecting primary production, in their winter quarters. The breeding dates of the same individuals in consecutive breeding seasons were advanced and clutch sizes were larger after winters with high NDVI in the winter quarters. Feather moult was also affected by winter conditions, with consequences for male sexual attractiveness. Length of tail ornament was positively correlated with NDVI during the previous winter, and males with large tail ornaments reproduced earlier and had larger clutches. The mean annual breeding date of the population was earlier and breeding success was increased after favourable winters, but this result was mainly determined by a single winter with very low NDVI. Thus, ecological conditions in Africa influence individual performance and productivity in a barn swallow population.

Age-independent telomere length predicts fitness in two bird species

Telomeres are dynamic DNA‐protein structures that form protective caps at the ends of eukaryotic chromosomes. Although initial telomere length is partly genetically determined, subsequent accelerated telomere shortening has been linked to elevated levels of oxidative stress. Recent studies show that short telomere length alone is insufficient to induce cellular senescence; advanced attrition of these repetitive DNA sequences does, however, reflect ageing processes. Furthermore, telomeres vary widely in length between individuals of the same age, suggesting that individuals differ in their exposure or response to telomere‐shortening stress factors. Here, we show that residual telomere length predicts fitness components in two phylogenetically distant bird species: longevity in sand martins, Riparia riparia, and lifetime reproductive success in dunlins, Calidris alpina. Our results therefore imply that individuals with longer than expected telomeres for their age are of higher quality.

SURVIVAL RATE OF ADULT BARN SWALLOWS HIRUNDO RUSTICA IN RELATION TO SEXUAL SELECTION AND REPRODUCTION

Sexual selection often affects individuals of the two sexes differently by imposing severe survival costs on individuals of the chosen sex, usually males. These costs may be energetic, physiological, mechanical, or ecological, and they can give rise to sex differences in survival. We studied survival rates of male and female adult Barn Swallows Hirundo rustica in a Danish population during 1984–1998, for the first time using capture–mark–recapture techniques to estimate the consequences of sexual selection for sex differences in survival. Males had slightly, but not significantly, higher survival than females. Females had annual survival estimates that were significantly more variable than those for males. Male annual survival rates were not positively correlated with those of females. Hence, different factors were hypothesized to affect male and female survival rate. Consistent with this prediction we found that annual male survival decreased with increasing annual mean length of the outermost tail feath...

Rapid evolutionary change in a secondary sexual character linked to climatic change

The ability of organisms to respond evolutionarily to rapid climatic change is poorly known. Secondary sexual characters show the potential for rapid evolutionary change, as evidenced by strong divergence among species and high evolvability. Here we show that the length of the outermost tail feathers of males of the socially monogamous barn swallow Hirundo rustica, feathers that provide a mating advantage to males, has increased by more than 1 standard deviation during the period from 1984 to 2003. Barn swallows from the Danish population studied here migrate through the Iberian Peninsula to South Africa in fall, and return along the same route in spring. Environmental conditions on the spring staging grounds in Algeria, as indexed by the Normalized Difference Vegetation Index, predicted tail length and change in tail length across generations. However, conditions in the winter quarters and at the breeding grounds did not predict change in tail length. Environmental conditions in Algeria in spring showed a temporal deterioration during the study period, associated with a reduction in annual survival rate of male barn swallows. Phenotypic plasticity in tail length of males, estimated as the increase in tail length from the age of 1 to 2 years, decreased during the course of the study. Estimates of directional selection differentials for male tail length with respect to mating success, breeding date, fecundity, survival and total selection showed temporal variation, with the intensity of breeding date selection, survival selection and total selection declining during the study. Response to selection as estimated from the product of heritability and total selection was very similar to the observed temporal change in tail length. These findings provide evidence of rapid micro‐evolutionary change in a secondary sexual character during a very short time period, which is associated with a rapid change in environmental conditions.

Consistent response of bird populations to climate change on two continents.

Birds populations allied in abundance Changes in climate can cause populations of species to decline, to increase, or to remain steady. Stephens et al. looked across species of common birds in Europe and the United States. Despite many differences between the two regions, expectations about how a species might respond to climate change did predict actual responses. Species predicted to benefit from increasing temperatures, or their associated effects, tended to increase, whereas those predicted to be negatively affected declined. Thus, even across widely varying ecological conditions and communities, climate change can be expected to alter population sizes. Science, this issue p. 84 The impact of climate change on population sizes of birds across continents can be predicted. Global climate change is a major threat to biodiversity. Large-scale analyses have generally focused on the impacts of climate change on the geographic ranges of species and on phenology, the timing of ecological phenomena. We used long-term monitoring of the abundance of breeding birds across Europe and the United States to produce, for both regions, composite population indices for two groups of species: those for which climate suitability has been either improving or declining since 1980. The ratio of these composite indices, the climate impact indicator (CII), reflects the divergent fates of species favored or disadvantaged by climate change. The trend in CII is positive and similar in the two regions. On both continents, interspecific and spatial variation in population abundance trends are well predicted by climate suitability trends.

Mixed species flocking of tits (Parus spp.): a field experiment

SummaryWe tested two general models of flocking behaviour, namely the antipredation model and foraging efficiency model on mixed-species tit flocks (Parus spp.). After food addition the size of mixed-species flocks was significantly less than in the control samples. In the presence of extra food significantly more birds were observed either in monospecific flocks or solitary, than during the control observations. In the presence of a living predator the birds foraged in larger mixed-specifies flocks than during the control observations. In addition, the social behaviour of Great Spotted Woodpecker, Middle Spotted Woodpecker and Nuthatch shifted to mixed-specific flocking. The size of monospecific flocks was independent of both treatments. The density of birds increased significantly after food addition, while in the predator presence the birds tended to leave the forest. These results support the view that both the antipredation model and foraging efficiency model seem to be valid for mixed-species flocking. However, in the case of monospecific flocks, the territory maintenance could be the most important factor.

Searching for potential wintering and migration areas of a Danish Barn Swallow population in South Africa by correlating NDVI with survival estimates

On the basis of correlation analyses between annual Normalised Difference Vegetation Index (NDVI) values in Africa and the annual survival rate estimated for a breeding population of barn swallows Hirundo rustica from Denmark, we identified potential wintering and migration areas in South Africa during December–February and March–May, when barn swallows commonly occur in South Africa. During December–February we identified potential wintering areas only in the western part of South Africa, in the Karoo. Potential areas in the central and eastern parts of the country were only identified during March–May. NDVI values in the Karoo during March–May explained most of the variance in annual adult survival rate of the population. The high ratio of European ringed barn swallows among controlled individuals in the Karoo was similar to the ratio that would be expected based on the number of ringed barn swallows and the population sizes of barn swallows in north-western European breeding populations. The level of this ratio in the Karoo was higher than in any other locality in the central and eastern parts of South Africa and Botswana, indicating that ringed birds from the eastern flyway are absent to a much smaller extent than ringed birds from the western flyway. This approach shows that the NDVI and survival method can focus ringing efforts to regions and areas that are likely to harbour specific breeding populations, thereby helping to identify potential wintering and migration areas for breeding populations of migratory birds.

Survival rates of Hungarian sand martins and their relationship with Sahel rainfall

Since 1986, I have carried out an intensive field survey of 10 000-30 000 pairs of a sand martin ( Riparia riparia ) population. Direct survey of the size and distribution of the breeding population and estimation of adult survival rates by SURGE, based on extensive ringing data sets, allow us to analyze the effects of different environmental factors with high precision. The model selection showed that the S s+t , P t model, in which the survival rates differ by sex for adults and vary in parallel by year and the capture rate varies by year, fits the data. The adult females had a lower survival rate compared to the males. The capture rate could be modelled as a quotient of the number of captured birds and the number of breeding birds along the upper part of the river Tisza. The survival rates of adults were related to the rainfall of the southern Sahel, which has an important role in the extension of the winter foraging habitat in the Sahel. Although the severe decrease in the population size, which may r...

Comparison of trace element and stable isotope approaches to the study of migratory connectivity: an example using two hirundine species breeding in Europe and wintering in Africa

Analyses of stable isotopes and trace elements in feathers may provide important information about location and habitat use during molt, thereby enabling the investigation of migratory connectivity and its ecological consequences in bird species that breed and winter in different areas. We have compared the conclusions arrived at based on the use of these two methods on the same samples of feathers from two migratory birds, the Sand Martin Riparia riparia and the Barn Swallow Hirundo rustica. We investigated the effects of location, age and sex on stable isotope (δ13C, δ15N, δD) and trace element profiles (As, Cd, Mg, Mn, Mo, Se, Sr, Co, Fe, Zn, Li, P, Ti, V, Ag, Cr, Ba, Hg, Pb, S, Ni and Cu). The feathers of adults at the breeding grounds were removed, forcing in birds to grow new feathers at the breeding grounds; this enabled a comparison of composition of feathers grown in Europe and Africa by the same individual. Stable isotope and trace element profiles varied geographically, even at micro-geographic scales, and also among age classes. The results of both methods suggest that food composition and/or source differs between adults and nestlings in the breeding area and that food and/or molting location changes with the age of individuals in Africa. In an attempt to determine the usefulness of data obtained from composition of feathers, we performed discriminant function analyses on information obtained on stable isotopes and trace elements in order to assess the correctness of the classification of group membership. When feathers molted in Africa were compared to those molted in Europe, trace element profiles of the 22 elements generally had a much greater resolution than the stable isotope profiles based on three stable isotopes. The proportion of correctly classified samples was also greater for analyses based on trace elements than for those based on stable isotopes.

Population trends of common breeding and wintering birds in Hungary, decline of longdistance migrant and farmland birds during 1999–2012

Abstract Based on the Hungarian common bird monitoring scheme (MMM), which is the longest running country-wide monitoring using formal sampling design with representative data for the main habitats in Central-Eastern Europe, we investigated the population trends of common breeding and wintering species. Habitat preference and occupancy of the common breeders, migration strategies and relationships among these characteristics could act behind the population trends. We pointed out that long distance migrant bird species had strong decreasing trends in Hungary and very probably in the entire Pannonian biogeographical region, whereas the partial and short migrant species has increasing trends. Farmland birds had declining trend, which trend became more obvious since the joining of Hungary to the EU. The negative changes in the farmland habitat could influence bird species nesting/foraging mainly in this habitat independently from their migration strategies. Our investigations let us to develop indicators on the basis of migration strategy and habitat usage of common birds to provide regular information about condition of groups of species and their habitats in Hungary and the Pannonian region. The MMM database provide unique opportunity for further investigations of several species, habitats and area specific in a part of Europe where this kind of information is rare yet. Összefoglalás A Mindennapi Madaraink Monitoringja (MMM) a leghosszabb ideje futó országos léptékű olyan monitorozó program Közép-, Kelet-Európában, amely random mintavételi stratégia alkalmazásával reprezentatív adatokkal szolgál a régió madárállományairól és főbb élőhelyeiről. Munkánkban a gyakori fészkelő és telelő fajok állomány trendjeit, a gyakori fészkelők élőhely preferenciáját és használatát, valamint vonulási stratégiáját vizsgáltuk az állományváltozások hátterében zajló folyamatok feltárása érdekében. Kimutattuk, hogy a hosszútávon vonuló madárfajok esetében jelentős állománycsökkenés van Magyarországon és feltehetően az egész Pannon biogeográfi ai régióban. Ugyanakkor a részlegesen és rövidtávon vonuló madárfajoknál növekedő állomány a jellemző. A mezőgazdasági élőhelyekhez kötődő fajoknál csökkenő állományok vannak, amely jelleg különösen Magyarország EU tagsága után erősödött fel. A mezőgazdasági élőhelyeken zajló kedvezőtlen változások az ott fészkelő/táplálkozó madárfajok helyzetét jelentősen befolyásolhatják e fajok vonulási stratégiájától függetlenül. Vizsgálatunk lehetőséget ad a gyakori madárfajok vonulási és élőhelyi jellemzőin alapuló olyan indikátorok fejlesztésére, amelyek rendszeres információval szolgálnak adott fajcsoportok és az azok által használt élőhelyek állapotáról Magyarországon és a Pannon régióban. Az MMM adatbázis egyedülálló lehetőséget ad nagyszámú faj, élőhely és terület további részletes vizsgálatára Európa olyan részén, ahol ezen információk még igen ritkák napjainkban.