Habitat selection, foraging niches and horizontal spacing of Willow Warbler Phylloscopus trochilus and Chiffchaff P. collybita in an area of sympatry

Habitat selection of the Willow Warbler and the Chiffchaff was studied along a succession of grey alder forest in Central Norway (63^oN) where both species breed. Both were found in all serai stages, but there was a slight tendency for the Willow Warbler to be found more often in the voungest stages than was the Chiffchaff.
Foraging niches and horizontal spacing were studied within one particular forest. Most of the records of both Willow Warbler and Chiffchaff came from the tree layer, and the overlap between the species in their foraging niches was considerable. However, the species were found to occupy almost mutually exclusive territories.     

Woodland area,species turnover and the conservation of bird assemblages in lowland England

A study over 4 years into the number of breeding bird species and species turnover (extinctions and colonisations) in relation to area was conducted in 35 woodlands, set in an intensively farmed landscape, in north-east Essex, UK. A total of 46 species was recorded. The number of species breeding increased with woodland area; the slope of the species–area relationship did not differ between years. Habitat diversity was the only other measured variable to influence species richness. Absolute species turnover was independent of woodland area but relative turnover declined with increase in woodland area. The numbers of territories of nine species were determined. For four summer visitors the number of woods occupied increased as the overall populations increased but, for the other species, changes in overall population size led to changes in numbers in occupied woods. Chaffinch Fringilla coelebs and Song Thrush Turdus philomelos were more associated with woodland edges, Nightingale Luscinia megarhynchos, Garden Warbler Sylvia borin, Chiffchaff Phylloscopus collybita and Willow Warbler P. trochilus with interiors. Several species showed an inverse relationship between population density and woodland area. Collections of small woods hold similar species richness to single large woods. While the acquisition of large woods for conservation purposes should be a priority, the extension of smaller woods to a size of about 10 ha would be highly beneficial to both the species richness and population stability of regional woodland bird assemblages.     

Using stable isotopes to link breeding population trends to winter ecology in Willow Warblers,Phylloscopus trochilus

Capsule Stable isotope composition of feathers grown in Africa indicates that Willow Warblers, Phylloscopus trochilus, breeding in areas of Britain experiencing different population trends may vary in their distribution, timing of moult and/or use of prey resources during the non-breeding season.

Aims To compare stable isotope ratios of feathers of Willow Warblers breeding in parts of Britain with differing rates of population change.

Methods Feathers were collected from three regions with differing recent population trends; northern Scotland (population increased), western Wales (declined slightly) and eastern England (declined rapidly). Collection occurred at ringing sites run by British Trust for Ornithology (BTO) volunteers as part of the Constant Effort Sites (CES) scheme between April and July in 2008 and 2009.

Results Willow Warblers from northern Scotland had significantly higher δ ¹⁵N and δ ¹³C values than those from eastern England, although the regional mean values did not differ greatly. There was no significant difference in δ ¹⁵N and δ ¹³C values between the sexes, but δ ¹⁵N values were significantly greater in individuals caught later in the breeding season.

Conclusions During the premigratory moult period in Africa, Willow Warblers from different parts of Britain may vary in their distribution, timing of moult and/or use of prey resources.     

Influence of climate change and postdelisting management on long‐term population viability of the conservation‐reliant Kirtland's Warbler

Rapid global climate change is resulting in novel abiotic and biotic conditions and interactions. Identifying management strategies that maximize probability of long‐term persistence requires an understanding of the vulnerability of species to environmental changes. We sought to quantify the vulnerability of Kirtland's Warbler (Setophaga kirtlandii), a rare Neotropical migratory songbird that breeds almost exclusively in the Lower Peninsula of Michigan and winters in the Bahamian Archipelago, to projected environmental changes on the breeding and wintering grounds. We developed a population‐level simulation model that incorporates the influence of annual environmental conditions on the breeding and wintering grounds, and parameterized the model using empirical relationships. We simulated independent and additive effects of reduced breeding grounds habitat quantity and quality, and wintering grounds habitat quality, on population viability. Our results indicated the Kirtland's Warbler population is stable under current environmental and management conditions. Reduced breeding grounds habitat quantity resulted in reductions of the stable population size, but did not cause extinction under the scenarios we examined. In contrast, projected large reductions in wintering grounds precipitation caused the population to decline, with risk of extinction magnified when breeding habitat quantity or quality also decreased. Our study indicates that probability of long‐term persistence for Kirtland's Warbler will depend on climate change impacts to wintering grounds habitat quality and contributes to the growing literature documenting the importance of considering the full annual cycle for understanding population dynamics of migratory species.     

Woodland structure,rather than tree identity,determines the breeding habitat of Willow Warblers Phylloscopus trochilus in the northwest of England

Capsule Woodland structure, rather than tree species, is the most important determinant of breeding habitat selection by Willow Warblers in North West England.

Aims To examine how habitat characteristics predict the occurrence of male Willow Warbler territories.

Methods Woodland structure (trunk density, trunk diameter, canopy cover and understory cover), tree species and food abundance were compared between woodland areas within and outside of male territories at a site in the UK.

Results Territories contained higher trunk numbers, had a narrow range of trunk diameters, and intermediate canopy cover. Food abundance did not differ with occupancy. Willow and alder were the most common trees within territories, in contrast to birch which has been found in previous studies. The habitat structure matches young woodlands, where birches often grow. However, at the study site the birches were large and mature, and therefore unsuitable. Moreover, woodland structure variables were better predictors of occupancy than any particular tree genera.

Conclusion The results indicate that vegetation structure, but not tree species or food availability, influence breeding habitat selection by Willow Warblers. The preferred structure is similar to coppice woodlands; therefore, the Willow Warbler decline may be linked to the loss of this traditional management across south England.     

Spatial and temporal variation in population trends in a long‐distance migratory bird

Aim 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. Location Britain and Ireland. Methods 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. Results 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. Main conclusion 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.     

Wing shape variation of Finnish and Central European Willow Warblers Phylloscopus trochilus and Chiffchaffs P. collybita

Wing shape variation of European Willow Warblers Phylloscopus trochilus and Chiffchaffs P. collybita was studied using indices calculated from wing formulae. Our data were from free-living local populations of P. t. acredula and P. c. abietinus from southern Finland, and P. t. trochilus and P. c. collybita from southwestern Germany.
There were no significant shape differences between the subspecies of the Willow Warbler in which sexual dimorphism was pronounced. The subspecies of the Chiffchaff were significantly different while the sexes were not. There were also significant differences between adult and immature individuals in the autumn. The intrapopulation variation must be considered in attempts to recognize different subspecies or populations in data on birds caught during migration.
In the Willow Warbler at least, the difference between age-groups was larger in males than in females. If the change in wing formula due to the complete pre-nuptial moult is similar in both sexes, juvenile males intermediate between adult females and adult males suffer disproportionately high mortality. It was earlier suggested that sexual selection increases body size in Willow Warbler males, but the present results imply additional selection pressures for increasing sexual dimorphism.     

Reproductive responses of two related coexisting songbird species to environmental changes: global warming, competition, and population sizes

Comparative analyses of interspecific differences in response to climate change can provide important insights into the factors initiating seasonal onset of reproduction in various species and subsequent fitness consequences. We present a comparative analysis based on a 30-year breeding survey of two related migratory songbird species [Reed Warbler Acrocephalus scirpaceus (RW) and Great Reed Warbler A. arundinaceus (GRW)], which coexist in reedbeds by means of various interspecific interactions. The RW advanced breeding by 15 days and shortened its breeding time window, which is a combined effect of higher temperatures, alleviated competition as a consequence of population declines in the dominant GRW, and reduced RW population. Although the breeding period of GRW changed only slightly, its clutch initiation was likewise related to temperature. Most probably, advanced breeding in RW is favoured by changes in food supply and accelerated reed growth, which provides the necessary nest concealment earlier, whereas this does not affect the GRW, a species less vulnerable to nest predation. Clutch size decreased later in the season, so that earlier breeding produced a net increase in both species. An additional increase of clutch size in GRW can be explained by the use of higher-quality territories in today’s smaller population. The main causes of nest losses were predation in RW and adverse weather in GRW, but reproductive success increased over the study period in both species, which was a consequence of larger clutches in RW, but of favourable weather during rearing and fewer total losses in GRW. Our results document that different causal mechanisms are involved in the reproductive changes of the two congeneric species living in the same habitat: RW breeding earlier by making use of competitive release and other ecological improvements, and GRW by benefiting from better rearing conditions. As species respond differentially to climate change depending on ecosystem and biotic interactions, predictions of population dynamics will remain vague until the specific response mechanisms have been elucidated.     

Population limitation in Palaearctic-African migrant passerines

We report the results of key factor analyses for Sedge Warbler Acrocephalus schoenobaenus, Blackcap Sylvia atricapilla, Whitethroat Sylvia communis and Willow Warbler Pftylloscopus Irochilus based on extensive data from the United Kingdom gathered by the British Trust for Ornithology. These results are compared with those from published key factor analyses based on intensive studies of Swallows Hirundo ruslica, Redstarts Phoenicurus phoenicums and three populations of Pied Flycatchers Fiiedula hypoleuca. Variation in losses between fledging and the following breeding season lk₄ ) accounted for most of the variation in total losses (K_T) for all populations. Breeding performance was poorly correlated with population changes. Density-dependence was found mainly in 6₄, its strength decreasing as average rate of population change increased. There was also evidence of weak density-dependence in the clutch size of Swallows and in Willow Warbler egg losses. Fluctuations in k₄ were correlated with conditions on the wintering grounds in Sedge Warblers, Whitethroats and Swallows, for the first two species these relationships being confirmed by analyses of independent survival estimates based on mark-recapture data. Populations of Sedge Warblers and Whitethroats appear to be limited by competition for resources on the wintering grounds. Removal experiments suggest that Willow Warblers, Pied Flycatchers and perhaps Blackcaps are limited through recruitment to the breeding population, in the case of Pied Flycatchers this limitation being in relation to the availability of nest sites.     

Long‐term changes in the migration phenology of UK breeding birds detected by large‐scale citizen science recording schemes

The timing of migration is one of the key life‐history parameters of migratory birds. It is expected to be under strong selection, to be sensitive to changing environmental conditions and to have implications for population dynamics. However, most phenological studies do not describe arrival and departure phenologies for a species in a way that is robust to potential biases, or that can be clearly related to breeding populations. This hampers our ability to understand more fully how climate change may affect species’ migratory strategies, their life histories and ultimately their population dynamics. Using generalized additive models (GAMs) and extensive large‐scale data collected in the UK over a 40‐year period, we present standardized measures of migration phenology for common migratory birds, and examine how the phenology of bird migration has changed in the UK since the 1960s. Arrival dates for 11 of 14 common migrants became significantly earlier, with six species advancing their arrival by more than 10 days. These comprised two species, Blackcap Sylvia atricapilla and Chiffchaff Phylloscopus collybita, which winter closest to Britain in southern Europe and the arid northern zone of Africa, Common Redstart Phoenicurus phoenicurus, which winters in the arid zone, and three hirundines (Sand Martin Riparia riparia, House Martin Delichon urbicum and Barn Swallow Hirundo rustica), which winter in different parts of Africa. Concurrently, departure dates became significantly later for four of the 14 species and included species that winter in southern Europe (Blackcap and Chiffchaff) and in humid zones of Africa (Garden Warbler Sylvia borin and Whinchat Saxicola rubetra). Common Swift Apus apus was the exception in departing significantly earlier. The net result of earlier arrival and later departure for most species was that length of stay has become significantly longer for nine of the 14 species. Species that have advanced their timing of arrival showed the most positive trends in abundance, in accordance with previous studies. Related in part to earlier arrival and the relationship above, we also show that species extending their stay in Great Britain have shown the most positive trends. Further applications of our modelling approach will provide opportunities for more robust tests of relationships between phenological change and population dynamics than have been possible previously.     

The interacting effects of food,spring temperature,and global climate cycles on population dynamics of a migratory songbird

Although long‐distance migratory songbirds are widely believed to be at risk from warming temperature trends, species capable of attempting more than one brood in a breeding season could benefit from extended breeding seasons in warmer springs. To evaluate local and global factors affecting population dynamics of the black‐throated blue warbler (Setophaga caerulescens), a double‐brooded long‐distance migrant, we used Pradel models to analyze 25 years of mark–recapture data collected in New Hampshire, USA. We assessed the effects of spring temperature (local weather) and the El Niño Southern Oscillation index (a global climate cycle), as well as predator abundance, insect biomass, and local conspecific density on population growth in the subsequent year. Local and global climatic conditions affected warbler populations in different ways. We found that warbler population growth was lower following El Niño years (which have been linked to poor survival in the wintering grounds and low fledging weights in the breeding grounds) than La Niña years. At a local scale, populations increased following years with warm springs and abundant late‐season food, but were unaffected by spring temperature following years when food was scarce. These results indicate that the warming temperature trends might have a positive effect on recruitment and population growth of black‐throated blue warblers if food abundance is sustained in breeding areas. In contrast, potential intensification of future El Niño events could negatively impact vital rates and populations of this species.     

Recent population declines in Afro‐Palaearctic migratory birds: the influence of breeding and non‐breeding seasons

Aim

Recent, rapid population declines in many Afro‐Palaearctic migratory bird species have focussed attention on changing conditions within Africa. However, processes influencing population change can operate throughout the annual cycle and throughout migratory ranges. Here, we explore the evidence for impacts of breeding and non‐breeding conditions on population trends of British breeding birds of varying migratory status and wintering ecology.

Location

Great Britain (England & Scotland).

Methods

Within‐ and between‐species variation in population trends is quantified for 46 bird species with differing migration strategies.

Results

Between 1994 and 2007, rates of population change in Scotland and England differed significantly for 19 resident and 15 long‐distance migrant species, but were similar for 12 short‐distance migrant species. Of the six long‐distance migrant species that winter in the arid zone of Africa, five are increasing in abundance throughout Britain. In contrast, the seven species wintering in the humid zone of Africa are all declining in England, but five of these are increasing in Scotland. Consequently, populations of both arid and humid zone species are increasing significantly faster in Scotland than England, and only the English breeding populations of species wintering in the humid zone are declining.

Main conclusions

Population declines in long‐distance migrants, especially those wintering in the humid zone, but not residents or short‐distance migrants suggest an influence of non‐breeding season conditions on population trends. However, the consistently less favourable population trends in England than Scotland of long‐distance migrant and resident species strongly suggest that variation in the quality of breeding grounds is influencing recent population changes. The declines in humid zone species in England, but not Scotland, may result from poorer breeding conditions in England exacerbating the impacts of non‐breeding conditions or the costs associated with a longer migration, while better conditions in Scotland may be buffering these impacts.

     

The phenology of spring bird migration to north Norway

Capsule There was no evidence of a long-term trend in arrival dates of spring migrants over the last 20 years in north Norway.

Aims To investigate the effect of climate on the timing of spring arrival of many species at their northern limit of breeding distribution and to seek evidence of any long-term trend.

Methods Observations of spring arrivals of 71 species into Troms, north Norway (69–70°N) between 1970 and 2000 by members of the local branch of the Norwegian Ornithological Society were analysed and related to available weather parameters.

Results The first migrants arrive in mid-March when air temperatures are still below 0°C and c. 1 m of snow is on the ground, with the main influx in late April and throughout May. By then much of the snow has melted and temperatures are c. 5°C. There was no evidence of a long-term trend in the median dates of arrival across 31 species in Troms between 1980 and 2000. However among 14 species for which detailed data exist in a limited area around Tromsø, the Golden Plover Pluvialis apricaria showed a significant trend towards an earlier arrival and the Willow Warbler Phylloscopus trochilus showed the opposite. Spring migration tended to be advanced during warm springs, and seven of the above subsets of 14 species showed significant negative correlations between their arrival dates and temperature. One showed a positive correlation.

Conclusion The data collected to date are a good baseline for future studies of the effects of climate change on migration phenology.     

Effects of flyway‐wide weather conditions and breeding habitat on the breeding abundance of migratory boreal waterbirds

Anthropogenic habitat loss and climate change are among the major threats to biodiversity. Bioclimatic zones such as the boreal and arctic regions are undergoing rapid environmental change, which will likely trigger changes in wildlife communities. Disentangling the effects of different drivers of environmental change on species is fundamental to better understand population dynamics under changing conditions. Therefore, in this study we investigate the synergistic effect of winter and summer weather conditions and habitat type on the abundance of 17 migratory boreal waterbird species breeding in Finland using three decades (1986–2015) of count data. We found that above‐average temperatures and precipitations across the western and northern range of the wintering grounds have a positive impact on breeding numbers in the following season, particularly for waterbirds breeding in eutrophic wetlands. Conversely, summer temperatures did not seem to affect waterbird abundance. Moreover, waterbird abundance was higher in eutrophic than in oligotrophic wetlands, but long term trends indicated that populations are decreasing faster in eutrophic than in oligotrophic wetlands. Our results suggest that global warming may apparently benefit waterbirds, e.g. by increased winter survival due to more favourable winter weather conditions. However, the observed population declines, particularly in eutrophic wetlands, may also indicate that the quality of breeding habitat is rapidly deteriorating through increased eutrophication in Finland which override the climatic effects. The findings of this study highlight the importance of embracing a holistic approach, from the level of a single catchment up to the whole flyway, in order to effectively address the threats that waterbirds face on their breeding as well as wintering grounds.     

中国柳莺属鸟类分类研究进展

柳莺属(Phylloscopus)是广泛分布于旧大陆地区的小型食虫鸟类,目前全世界已知66种,其中约50种见于亚洲。该属鸟类外部形态十分相近且同域分布种数较多,历来是鸟类分类学中的研究难点及热点。2003年贾陈喜等介绍了20世纪90年代以来发表的分布于我国的柳莺属鸟类新种及相关分类学变动,涉及3个新描述种和9个由亚种提升的种,共计30种26亚种。2003年以来关于柳莺属鸟类的分类学研究取得了许多新的成果,同时我国境内也发现了一些新的分布记录。综合最新的文献及分布资料,整理得知我国现有柳莺属鸟类41种31亚种,与2003年的状况相比已有较大的变化。主要表现在:新描述种方面,德国学者Martens等2008年描述了黄腹柳莺(P.affinis)种组中的一新种———华西柳莺(P.occisinensis);2010年瑞典学者Alstrm等报道在越南和老挝地区新发现的灰岩柳莺(P.calciatilis)已被证实在我国有分布;亚种提升为种方面,如日本柳莺(P.xanthodryas)自极北柳莺(P.borealis)中独立,冠纹柳莺(P.claudiae)和西南冠纹柳莺(P.reguloides)分开等;分类地位再评议方面,如灰头鹟莺(Seicercusxanthoschistos)实为灰头柳莺(P.xanthoschistos)等;新分布纪录方面,如欧柳莺(P.trochilus)在内蒙古达里诺尔湖地区发现确切记录等。现今对柳莺属鸟类分类学方面的研究已明显呈现出传统形态学、分子遗传学、声谱分析及野外鸣声回放实验等新老技术手段相整合,多方面多角度地阐述问题的局面。中国是世界柳莺属鸟种分布最多的国家(其中有9种仅在或主要于我国境内繁殖),但我国鸟类学者关于该属鸟类的研究工作并不多见。柳莺属鸟类在分类学和进化生物学等领域具有重要的研究价值,我国鸟类学工作者应当引起足够的重视和关注。     

Polygyny in Willow Warblers <Emphasis Type="Italic">Phylloscopus trochilus</Emphasis> (Sylviidae,Passeriformes) in Middle European Russia: Differences in songs of polygynous and monogynous males

The study was performed in May to July of 1995 in Middle Russia (Skadovskii Zvenigorod Biostation, MSU, Moscow oblast: 55°44′ N, 36°51′ E). Monoterritorial polygyny was observed in one of seven studied Willow Warbler males Phylloscopus trochilus. The distance between the nests of the first and second females was 90 m. In the nest of the first female, five nestlings hatched on June 10 and the flight of the fledglings occurred on June 23. In the nest of the second female, a 5-to 6-day-old nestling of the cuckoo Cuculus canorus was found on June 18. The male actively participated in feeding the young in the first nest and did not participate in the feeding of the young in the second nest. The songs of the bigamous male differ significantly from the songs of monogamous males in the middle and final parts of the breeding cycle. The song of the bigamous male in the idle and end of the breeding season is similar to that in the beginning of the breeding season. Unmated males in the middle of the breeding season also retain a more permanent structure of their songs in comparison with breeding males. This case of polygyny seems to be related to special characteristics of the males such as their singing activity and the structure of their songs.     

Willow Warbler Phylloscopus trochilus habitat in woods with different structure and management in southern England

Capsule Use of Light Detection and Ranging (LiDAR) data identified suitable Willow Warbler habitat based on mean vegetation height. This habitat model provided maps of distribution and occupation of suitable habitat.

Aims To identify habitat associations in woods with different vegetation structure and management systems during a period of low Willow Warbler populations.

Methods Locations of all Willow Warblers were mapped during the breeding season in three woods of contrasting management; recent low intervention, actively coppiced woodland and high forest with clear‐fells. Height profile models of each wood were derived from airborne LiDAR. The mean vegetation height at locations with Willow Warblers and a sample from the rest of the wood were used to produce models of optimum habitat and breadth of habitat occupied in each wood. The habitat model was then used to produce maps of suitable habitat.

Results The habitat models did not differ between woods, with highest probability of Willow Warbler occurrence in mean vegetation heights of 3.7–5.3 m. Habitat of heights 6–11 m appeared less suitable, being only partly occupied. Habitat maps showed that habitat of suitable height was only occupied when it occurred as large patches; smaller patches (mostly <0.5 ha) and edges along rides and fields were not used.

Conclusion The use of LiDAR derived measures of vegetation height identified areas of suitable habitat for Willow Warblers. Willow Warblers occupied areas of low mean vegetation height either as early successional or open canopy woodland in all woods. Height‐based habitat maps can identify areas of suitable habitat within larger expanses of heterogeneous woodland and are a potentially useful tool in assessing changes in extent of what are often temporary patches of habitat.     

Autumn bird migration phenology: A potpourri of wind,precipitation and temperature effects

Climate change has caused a clear and univocal trend towards advancement in spring phenology. Changes in autumn phenology are much more diverse, with advancement, delays, and ‘no change' all occurring frequently. For migratory birds, patterns in autumn migration phenology trends have been identified based on ecological and life‐history traits. Explaining interspecific variation has nevertheless been challenging, and the underlying mechanisms have remained elusive. Radar studies on non‐species‐specific autumn migration intensity have repeatedly suggested that there are strong links with weather. In long‐term species‐specific studies, the variance in autumn migration phenology explained by weather has, nevertheless, been rather low, or a relationship was even lacking entirely. We performed a spatially explicit time window analysis of weather effects on mean autumn passage of four trans‐Saharan and six intra‐European passerines to gain insights into this apparent contradiction. We analysed data from standardized daily captures at the Heligoland island constant‐effort site (Germany), in combination with gridded daily temperature, precipitation and wind data over a 55‐year period (1960–2014), across northern Europe. Weather variables at the breeding and stopover grounds explained up to 80% of the species‐specific interannual variability in autumn passage. Overall, wind conditions were most important. For intra‐European migrants, wind was even twice as important as either temperature or precipitation, and the pattern also held in terms of relative contributions of each climate variable to the temporal trends in autumn phenology. For the trans‐Saharan migrants, however, the pattern of relative trend contributions was completely reversed. Temperature and precipitation had strong trend contributions, while wind conditions had only a minor impact because they did not show any strong temporal trends. As such, understanding species‐specific effects of climate on autumn phenology not only provides unique insights into each species' ecology but also how these effects shape the observed interspecific heterogeneity in autumn phenological trends.     

Is earlier spring migration of Tatarstan warblers expected under climate warming?

We analysed data on the arrival dates of four species of leaf warbler (genus Phylloscopus) collected in Tatarstan between 1957 and 2004. There was no evidence over the whole period that the warblers returned to their breeding sites significantly earlier, mainly because local temperatures for April and May, months when the majority of birds arrived from their wintering grounds, did not increase significantly. However, arrival dates of two species (Chiffchaff P. collybita and Willow warbler P.trochilus) were strongly related to local temperature in April, and that of Greenish warbler P. trochiloides to that in May. As expected, arrival dates for the three species wintering in Africa (Chiffchaff, Willow and Wood warblers P. sibilatrix) correlated positively with one another (P < 0.01 in all cases), but were not correlated with arrival dates of Greenish warbler (P > 0.5 in all cases), a species wintering in the Indian sub-continent.