Explore the vast range of titles available.

1. Male-biased sex ratios occur in many bird species, particularly in those with small or declining populations, but the causes of these skews and their consequences for local population demography are rarely known. Within-species variation in sex ratios can help to identify the demographic and behavioural processes associated with such biases. 2. Small populations may be more likely to have skewed sex ratios if sex differences in survival, recruitment or dispersal vary with local abundance. Analyses of species with highly variable local abundances can help to identify these mechanisms and the implications for spatial variation in demography. Many migratory bird species are currently undergoing rapid and severe declines in abundance in parts of their breeding ranges and thus have sufficient spatial variation in abundance to explore the extent of sex ratio biases, their causes and implications. 3. Using national-scale bird ringing data for one such species (willow warbler, Phylloscopus trochilus), we show that sex ratios vary greatly across Britain and that male-biased sites are more frequent in areas of low abundance, which are now widespread across much of south and east England. These sex ratio biases are sufficient to impact local productivity, as the relative number of juveniles caught at survey sites declines significantly with increasing sex ratio skew. 4. Sex differences in survival could influence this sex ratio variation, but we find little evidence for sex differences in survival increasing with sex ratio skew. In addition, sex ratios have become male-biased over the last two decades, but there are no such trends in adult survival rates for males or females. This suggests that lower female recruitment into low abundance sites is contributing to these skews. 5. These findings suggest that male-biased sex ratios in small and declining populations can arise through local-scale sex differences in survival and dispersal, with females recruiting disproportionately into larger populations. Given the high level of spatial variation in population declines and abundance of many migratory bird species across Europe at present, malebiased small populations may be increasingly common. As singing males are the primary records used in surveys of these species, and as unpaired males often sing throughout the breeding season, local sex ratio biases could also be masking the true extent of these population declines.

What draws us to the beauty of a peacock, the flight of an eagle, or the song of a nightingale? Why are birds so significant in our lives and our sense of the world? And what do our ways of thinking about and experiencing birds tell us about ourselves? Birdscapes is a unique meditation on the variety of human responses to birds, from antiquity to today, and from casual observers to the globe-trotting \"twitchers\" who sometimes risk life, limb, and marriages simply to add new species to their \"life lists.\" Drawing extensively on literature, history, philosophy, and science, Jeremy Mynott puts his own experiences as a birdwatcher in a rich cultural context. His sources range from the familiar--Thoreau, Keats, Darwin, and Audubon--to the unexpected--Benjamin Franklin, Giacomo Puccini, Oscar Wilde, and Monty Python. Just as unusual are the extensive illustrations, which explore our perceptions and representations of birds through images such as national emblems, women's hats, professional sports logos, and a Christmas biscuit tin, as well as classics of bird art. Each chapter takes up a new theme--from rarity, beauty, and sound to conservation, naming, and symbolism--and is set in a new place, as Mynott travels from his \"home patch\" in Suffolk, England, to his \"away patch\" in New York City's Central Park, as well as to Russia, Australia, and Greece. Conversational, playful, and witty, Birdscapes gently leads us to reflect on large questions about our relation to birds and the natural world. It encourages birders to see their pursuits in a broader human context--and it shows nonbirders what they may be missing.

Protandry is a widespread life‐history phenomenon describing how males precede females at the site or state of reproduction. In migratory birds, protandry has an important influence on individual fitness, the migratory syndrome, and phenological response to climate change. Despite its significance, accurate analyses on the dynamics of protandry using data sets collected at the breeding site, are lacking. Basing our study on records collected during two time periods, 1979 to 1988 and 2006 to 2016, we aim to investigate protandry dynamics over 38 years in a breeding population of willow warblers (Phylloscopus trochilus). Change in the timing of arrival was analyzed in males and females, and protandry (number of days between male and female arrival) was investigated both at population level and within breeding pairs. Our results show advancement in the arrival time at the breeding site in both sexes, but male arrival has advanced to a greater extent, leading to an increase in protandry both at the population level and within breeding pairs. We did not observe any change in sex ratio that could explain the protandry increase, but pronounced temperature change has occurred and been reported in the breeding area and along the migratory route. Typically, natural selection opposes too early arrival in males, but given warmer springs, this counteracting force may be relaxing, enabling an increase in protandry. We discuss whether our results suggest that climate change has induced sex‐specific effects, if these could be evolutionary and whether the timing of important life‐history stages such as arrival at the breeding site may change at different rates in males and females following environmental shifts. Protandry is a widespread phenomenon in nature, influential on several aspects of life history in migratory birds. Despite its significance, accurate analyses are lacking on its dynamics. Here, using a unique data set spanning 38 years, we show how protandry has increased over time during a period of temperature warming, suggesting that climate change may have cause sex‐specific effects in the willow warbler.

The arrival of many species of migrant passerine in the European spring has shifted earlier over recent decades, attributed to climate change and rising temperatures in Europe and west Africa. Few studies have shown the effects of climate change in both hemispheres though many long-distance migrants use wintering grounds which span Africa. The migrants' arrival in Europe thus potentially reflects a combination of the conditions they experience across Africa. We examine if the timing of spring migration of a long-distance migrant, the Willow Warbler, is related to large-scale climate indices across Africa and Europe. Using data from daily mistnetting from 1 April to 15 May in 1982-2017 at Bukowo (Poland, Baltic Sea coast), we developed an Annual Anomaly metric (AA, in days) to estimate how early or late Willow Warblers arrive each spring in relation to their multi-year average pattern. The Willow Warblers' spring passage advanced by 5.4 days over the 36 years. We modelled AA using 14 potential explanatory variables in multiple regression models. The variables were the calendar year and 13 large-scale indices of climate in Africa and Europe averaged over biologically meaningful periods of two to four months during the year before spring migration. The best model explained 59% of the variation in AA with seven variables: Northern Atlantic Oscillation (two periods), Indian Ocean Dipole, Southern Oscillation Index, Sahel Precipitation Anomaly, Scandinavian Index and local mean temperatures. The study also confirmed that a long-term trend for Willow Warblers to arrive earlier in spring continued up to 2017. Our results suggest that the timing of Willow Warbler spring migration at the Baltic Sea coast is related to a summation of the ecological conditions they had encountered over the previous year during breeding, migration south, wintering in Africa and migration north. We suggest these large-scale climate indices reflect ecological drivers for phenological changes in species with complex migration patterns and discuss the ways in which each of the seven climate indices could be related to spring migration at the Baltic Sea coast.

Meteorological conditions influence strongly the energy and water budget of birds. By adjusting their flights spatially and temporally with respect to these conditions, birds can reduce their energy expenditure and water loss considerably. By radar, we quantified songbird migration across the western Sahara in spring and autumn. There autumn migrants face the trade-off between (a) favorable winds combined with hot and dry air at low altitudes and (b) unfavorable winds combined with humid and cold air higher up. Thus, it can be tested whether birds may chose altitudes to minimize water loss instead of energy expenditure. We predicted optimal flight altitudes with respect to water loss and energy expenditure based on a physiological flight model when crossing the western Sahara and compared these model predictions spatially and temporally with measured songbird densities. The model aiming for minimal water consumption predicted a mean flight altitude of 3,400 m under autumn conditions. However, 64% of the nocturnal songbird migration flew at altitudes below 1,000 m above ground level profiting from tailwind. This preference for tailwind in autumn, despite the hot and dry air, emphasizes the importance of energy savings and diminishes the significance of possible water stress for the selection of flight altitude. Nevertheless, during daytime, high energy expenditure due to air turbulences and water loss due to warmer air and direct solar radiation prevent songbirds from prolonging their nocturnal flights regularly into the day. Birds crossing the Sahara save water by nocturnal flights and diurnal rests.

Over the past three decades, evidence has been growing that many Afro-Palaearctic migratory bird populations have suffered sustained and severe declines. As causes of these declines exist across both the breeding and non-breeding season, identifying potential drivers of population change is complex. In order to explore the roles of changes in regional and local environmental conditions on population change, we examine spatial and temporal variation in population trajectories of one of Europe's most abundant Afro-Palaearctic summer migrants, the willow warbler, Phylloscopus trochilus. Britain and Ireland. We use national survey data from Britain and Ireland (BBS: BTO/RSPB/JNCC Breeding Bird Survey and CBS: BWI/NPWS/Heritage Council Countryside Breeding Survey) from 1994 to 2006 to model the spatial and temporal variation in willow warbler population trends. Across Britain and Ireland, population trends follow a gradient from sharp declines in the south and east of England to shallow declines and/or slight increases in parts of north and west England, across Scotland and Ireland. Decreasing the spatial scale of analysis reveals variation in both the rate and spatial extent of population change within central England and the majority of Scotland. The rates of population change also vary temporally; declines in the south of England are shallower now than at the start of the time series, whereas populations further north in Britain have undergone periods of increase and decline. These patterns suggest that regional-scale drivers, such as changing climatic conditions, and local-scale processes, such as habitat change, are interacting to produce spatially variable population trends. We discuss the potential mechanisms underlying these interactions and the challenges in addressing such changes at scales relevant to migratory species.

INTRODUCTION: In contact zones, genetic mixing of two taxa can be restricted by prezygotic (e.g. assortative mating) or postzygotic (lower fitness of hybrid offspring) barriers, or a combination of the two. A hybrid zone between two willow warbler subspecies (Phylloscopus trochilus trochilus, P. t. acredula) with distinctive migratory strategies occurs in central Sweden. These subspecies exhibit differences in migratory direction and distance, resulting in geographically distinct wintering areas in Africa. The subspecies may have diverged from a common refuge after the last ice age, and neutral genetic markers are homogeneous across their range. By contrast, several phenotypic traits and genetic markers of two chromosomal regions previously identified show steep clines across the divide. The evolutionary forces that maintain this migratory divide remain unknown. Here we use plumage colour, morphology, genetic markers and feather stable nitrogen-isotopes (δ ¹⁵N) to assess if assortative mating between migratory phenotypes could be acting as a possible mechanism for keeping the two forms genetically separate and maintaining the migratory divide. We colour-ringed a willow warbler breeding population in the central part of the hybrid zone and observed the breeding population to assess phenotypic and genotypic traits of social pairs. RESULTS: Our data suggest that wintering area and genetic ancestry had an effect on male arrival time to the breeding grounds which could contribute to assortment. However, evidence for assortative mating could not be detected based on a comparison of plumage colour, morphology and δ ¹⁵N between social mates. CONCLUSION: This finding was strengthened by analyses of subspecies-specific genetic markers, which allowed us to identify the presence of a large proportion of potential hybrids and backcrosses at the study site. Our results supported the hypothesis that pre-mating isolation in willow warblers is weak, resulting in extensive hybridisation across the migratory divide.

Rare Birds of North Americais the first comprehensive illustrated guide to the vagrant birds that occur throughout the United States and Canada. Featuring 275 stunning color plates, this book covers 262 species originating from three very different regions--the Old World, the New World tropics, and the world's oceans. It explains the causes of avian vagrancy and breaks down patterns of occurrence by region and season, enabling readers to see where, when, and why each species occurs in North America. Detailed species accounts describe key identification features, taxonomy, age, sex, distribution, and status. Rare Birds of North Americaprovides unparalleled insights into vagrancy and avian migration, and will enrich the birding experience of anyone interested in finding and observing rare birds. Covers 262 species of vagrant birds found in the United States and CanadaFeatures 275 stunning color plates that depict every speciesExplains patterns of occurrence by region and seasonProvides an invaluable overview of vagrancy patterns and migrationIncludes detailed species accounts and cutting-edge identification tips

On the basis of a long-term study of passerines in the Lower Ob’ region, data were obtained on the beginning and duration of arrival and flying away, reproduction periods, and post-breeding and post-juvenile molting. The triggering factors are discussed in this paper.