Rain,prey and predators: climatically driven shifts in frog abundance modify reproductive allometry in a tropical snake

To predict the impacts of climate change on animal populations, we need long-term data sets on the effects of annual climatic variation on the demographic traits (growth, survival, reproductive output) that determine population viability. One frequent complication is that fecundity also depends upon maternal body size, a trait that often spans a wide range within a single population. During an eight-year field study, we measured annual variation in weather conditions, frog abundance and snake reproduction on a floodplain in the Australian wet-dry tropics. Frog numbers varied considerably from year to year, and were highest in years with hotter wetter conditions during the monsoonal season (“wet season”). Mean maternal body sizes, egg sizes and post-partum maternal body conditions of frog-eating snakes (keelback, Tropidonophis mairii, Colubridae) showed no significant annual variation over this period, but mean clutch sizes were higher in years with higher prey abundance. Larger females were more sensitive to frog abundance in this respect than were smaller conspecifics, so that the rate at which fecundity increased with body size varied among years, and was highest when prey availability was greatest. Thus, the link between female body size and reproductive output varied among years, with climatic factors modifying the relative reproductive rates of larger (older) versus smaller (younger) animals within the keelback population.     

Individual fitness and the effects of a changing climate on the cessation and length of the breeding period using a 34‐year study of a temperate songbird

Studies of the phenological responses of animals to climate change typically emphasize the initiation of breeding although climatic effects on the cessation and length of the breeding period may be as or more influential of fitness. We quantified links between climate, the cessation and length of the breeding period, and individual survival and reproduction using a 34‐year study of a resident song sparrow (Melospiza melodia) population subject to dramatic variation in climate. We show that the cessation and length of the breeding period varied strongly across years, and predicted female annual fecundity but not survival. Breeding period length was more influential of fecundity than initiation or cessation of breeding alone. Warmer annual temperature and drier winters and summers predicted an earlier cessation of breeding. Population density, the date breeding was initiated, a female's history of breeding success, and the number of breeding attempts initiated previously also predicted the cessation of breeding annually, indicating that climatic, population, and individual factors may interact to affect breeding phenology. Linking climate projections to our model results suggests that females will both initiate and cease breeding earlier in the future; this will have opposite effects on individual reproductive rate because breeding earlier is expected to increase fecundity, whereas ceasing breeding earlier should reduce it. Identifying factors affecting the cessation and length of the breeding period in multiparous species may be essential to predicting individual fitness and population demography. Given a rich history of studies on the initiation of breeding in free‐living species, re‐visiting those data to estimate climatic effects on the cessation and length of breeding should improve our ability to predict the impacts of climate change on multiparous species.     

Temperature and egg-laying experience influence breeding performance of captive female houbara bustards

The influence of climate, age and egg-laying experience on reproductive performance (propensity, fecundity, timing) of a flock of captive houbara bustards was determined. The flock, established in Saudi Arabia for reintroduction purposes, was housed in outdoor pens, and fed food and water ad libitum. Birds were artificially inseminated when they came into breeding condition and eggs were removed soon after laying. Winter temperatures, rather than rainfall, synchronized reproduction in the captive flock. Cooler winter temperatures led to higher proportions of females laying, an earlier start to laying, and greater numbers of eggs laid per season. The first significant rainfall of the season stimulated some females to lay their last egg. Age per se had little effect on breeding performance independent of egg-laying experience. Females with no previous egg-laying experience laid fewer eggs than similarly aged females with previous experience. This difference, in combination with a pattern of increasing recruitment into the breeding population between 1 and 5 years of age, led to improved breeding performance in the population with age. The inferior performance of first-time egg-layers, despite ad libitum food, indicates restraint in the onset of breeding, which may be an adaptation for optimizing life-time fitness.     

Dispersal and climate change: a case study of the Arctic tern Sterna paradisaea

Dispersal is an important evolutionary process that can affect admixture of populations and cause rapid responses to changing climatic conditions due to gene flow from populations at different altitudes or latitudes already experiencing these conditions. We investigated long-term patterns of natal and breeding dispersal in a coastal seabird, the Arctic tern Sterna paradisaea , that experiences specific climatic conditions in the northern temperate and Arctic climate zones during breeding and different climatic conditions in the Antarctic during winter. Long natal and breeding dispersal distances were costly as shown by their effects on delayed breeding. Dispersal distances varied significantly among years, with natal dispersal showing a strong temporal increase during the last 70 years. Annual differences in dispersal distance could be accounted for by climate conditions in the breeding grounds and the winter quarters. Natal dispersal was related to climate conditions in both the year of hatching and the year of breeding, whereas breeding dispersal was only related to climate conditions in the second year of the dispersal event. Only the north Atlantic oscillation (NAO) index for winter showed a consistent temporal trend, suggesting that the temporal trend in natal dispersal distance must be caused by changes in the NAO (or associated phenomena). These findings indicate that dispersal can change rapidly in response to changing climate conditions.     

Climatic effects on the breeding phenology and reproductive success of an arctic-nesting goose species

Climate warming is pronounced in the Arctic and migratory birds are expected to be among the most affected species. We examined the effects of local and regional climatic variations on the breeding phenology and reproductive success of greater snow geese ( Chen caerulescens atlantica ), a migratory species nesting in the Canadian Arctic. We used a long-term dataset based on the monitoring of 5447 nests and the measurements of 19 234 goslings over 16 years (1989–2004) on Bylot Island. About 50% of variation in the reproductive phenology of individuals was explained by spring climatic factors. High mean temperatures and, to a lesser extent, low snow cover in spring were associated with an increase in nest density and early egg-laying and hatching dates. High temperature in spring and high early summer rainfall were positively related to nesting success. These effects may result from a reduction in egg predation rate when the density of nesting geese is high and when increased water availability allows females to stay close to their nest during incubation recesses. Summer brood loss and production of young at the end of the summer increased when values of the summer Arctic Oscillation (AO) index were either very positive (low temperatures) or very negative (high temperatures), indicating that these components of the breeding success were most influenced by the regional summer climate. Gosling mass and size near fledging were reduced in years with high spring temperatures. This effect is likely due to a reduced availability of high quality food in years with early spring, either due to food depletion resulting from high brood density or a mismatch between hatching date of goslings and the timing of the peak of plant quality. Our analysis suggests that climate warming should advance the reproductive phenology of geese, but that high spring temperatures and extreme values of the summer AO index may decrease their reproductive success up to fledging.     

Climate change, migratory connctivity and changes in laying date and clutch size of the pied flycatcher

We examined long-term (1943–2003) variability in laying dates and clutch sizes in a Finnish population of the pied flycatcher Ficedula hypoleuca Pallas, and analysed whether potential changes were explained by changes in climatic factors at the wintering area in Africa, at migration route or at breeding grounds. Among-year variation in both mean and skewness of laying dates increased, which for mean laying date appeared to be explained by variability of temperatures at the breeding grounds and for skewness by variable temperature trends along the migration route. Pied flycatchers bred earlier in warm springs, but despite a warming trend in pre-laying temperatures, the laying dates tended to delay. Laying dates became continuously later in relation to the phenology of the environment. Mean clutch size decreased with time when mean laying date was controlled for, but the climatic factors did not appear to explain the decrease. The advancement of spring phenology may have shifted some food sources needed for egg-laying, thus leading to later laying and smaller clutches. Variation in clutch size increased when wintering conditions were favourable so that clutch size distribution was skewed with a tail of small clutches when there had been lot of rainfall (more vegetation and insects) in the wintering area. We suggest that when ecological conditions during winter were good, the tail of small clutches represented low-quality individuals that were not able to breed after bad winters. Our analyses demonstrate that measures of spread and symmetry give different information about population level changes than means, and thus complement the understanding of the potential influences of climate change on populations.     

Advances in laying date and increasing population size suggest positive responses to climate change in Common Eiders Somateria mollissima in Iceland

Models of climate change predict that its effects on animal populations will not always be negative, but most studies indicate negative associations between changes in climate and the phenology of animal migration and reproduction. For some populations, however, climate change may render particular environments more favourable, with positive effects on population growth. We used a 30-year population dataset on over 2000 Common Eiders Somateria mollissima at a colony in southwest Iceland to examine the response of this species to climate fluctuations. Eiders are strongly dependent on suitable climatic conditions for successful reproduction and survival. Temperatures in southwest Iceland, in both winter and summer, have generally increased over the past 30 years but have shown considerable fluctuation. We show that females laid earlier following mild winters and that year-to-year variation in the number of nests was related to the temperature during the breeding season 2 years previously. Milder summers could have positive effects on breeding success and offspring survival, producing an increase in nest numbers 2 years later when most Eiders recruit into the breeding population. In this part of their range, Eiders could benefit from a general warming of the climate.     

Phenological delay despite warming in wood frog Rana sylvatica reproductive timing: a 20-year study

Across all taxa, amphibians exhibit some of the strongest phenological shifts in response to climate change. As climates warm, amphibians and other animals are expected to breed earlier in response to temperature cues. However, if species use fixed cues such as daylight, their breeding timing might remain fixed, potentially creating disconnects between their life history and environmental conditions. Wood frogs Rana sylvatica are a cold-adapted species that reproduce in early spring, immediately after breeding ponds are free of ice. We used long-term surveys of wood frog oviposition timing in 64 breeding ponds over 20 yr to show that, despite experiencing a warming of 0.29°C per decade in annual temperature, wood frog breeding phenology has shifted later by 2.8 d since 2000 (1.4 d per decade; 4.8 d per °C). This counterintuitive pattern is likely the result of changes in the timing of snowpack accumulation and melting. Finally, we used relationships between climate and oviposition between 2000 and 2018 to hindcast oviposition dates from climate records to model longer-term trends since 1980. Our study indicates that species can respond to fine-grained seasonal climate heterogeneity within years that is not apparent or counterintuitive when related to annual trends across years.     

Are heat waves susceptible to mitigate the expansion of a species progressing with global warming?

A number of organisms, especially insects, are extending their range in response of the increasing trend of warmer temperatures. However, the effects of more frequent climatic anomalies on these species are not clearly known. The pine processionary moth, Thaumetopoea pityocampa, is a forest pest that is currently extending its geographical distribution in Europe in response to climate warming. However, its population density largely decreased in its northern expansion range (near Paris, France) the year following the 2003 heat wave. In this study, we tested whether the 2003 heat wave could have killed a large part of egg masses. First, the local heat wave intensity was determined. Then, an outdoor experiment was conducted to measure the deviation between the temperatures recorded by weather stations and those observed within sun‐exposed egg masses. A second experiment was conducted under laboratory conditions to simulate heat wave conditions (with night/day temperatures of 20/32°C and 20/40°C compared to the control treatment 13/20°C) and measure the potential effects of this heat wave on egg masses. No effects were noticed on egg development. Then, larvae hatched from these egg masses were reared under mild conditions until the third instar and no delayed effects on the development of larvae were found. Instead of eggs, the 2003 heat wave had probably affected directly or indirectly the young larvae that were already hatched when it occurred. Our results suggest that the effects of extreme climatic anomalies occurring over narrow time windows are difficult to determine because they strongly depend on the life stage of the species exposed to these anomalies. However, these effects could potentially reduce or enhance the average warming effects. As extreme weather conditions are predicted to become more frequent in the future, it is necessary to disentangle the effects of the warming trend from the effects of climatic anomalies when predicting the response of a species to climate change.     

Ocean temperature and density dependence as key drivers of the population dynamics of an intertidal crab at the Brazilian oceanic islands

Understanding how climatic and density-dependent processes affect demography is crucial for predicting population responses to climate change. For marine invertebrates with complex life cycle such as decapod crustaceans, increasing temperatures might affect survival and development of early pelagic stages, whereas high density can increase competition and thus reduce growth and fecundity of older life stages. In this study, we investigate the effects of warm ocean events, body size and density on the population dynamics of the intertidal Sally lightfoot crab (Grapsus grapsus) at the Brazilian oceanic islands. Firstly, we assessed the trends of marine heatwaves (MHW) and positive temperature anomalies (ΔSST+) at the equatorial St Peter and St Paul (SPSP) Archipelago and Rocas Atoll and the subtropical Trindade Island. We then jointly analyzed short-term count, capture-recapture and fecundity data, and long-term population monitoring data (2003–2019) using an integrated population model. Warm ocean events have become more frequent and intense only at the equatorial islands. Increasing MHW frequency positively influenced recruitment in the high-density SPSP population, while MHW intensity and ΔSST+ frequency had negative impacts. Conversely, no climatic effects were observed for the low-density Rocas population, which has the largest crabs. Despite a lack of warming in Trindade, this subtropical population with intermediate density and body size was negatively affected by ΔSST+. Our findings revealed population-specific responses to climate change when accounting for local life history and ecology. Thus, environmental and density-dependent effects should be broadly considered in future conservation studies regarding ocean warming impacts on marine invertebrate populations.     

Warmer winters reduce frog fecundity and shift breeding phenology,which consequently alters larval development and metamorphic timing

One widely documented phenological response to climate change is the earlier occurrence of spring‐breeding events. While such climate change‐driven shifts in phenology are common, their consequences for individuals and populations have rarely been investigated. I addressed this gap in our knowledge by using a multi‐year observational study of six wood frog (Rana sylvatica) populations near the southern edge of their range. I tested first if winter temperature or precipitation affected the date of breeding and female fecundity, and second if timing of breeding affected subsequent larval development rate, mass at metamorphosis, date of metamorphosis, and survival. Warmer winters were associated with earlier breeding but reduced female fecundity. Winter precipitation did not affect breeding date, but was positively associated with female fecundity. There was no association between earlier breeding and larval survival or mass at metamorphosis, but earlier breeding was associated with delayed larval development. The delay in larval development was explained through a counterintuitive correlation between breeding date and temperature during larval development. Warmer winters led to earlier breeding, which in turn was associated with cooler post‐breeding temperatures that slowed larval development. The delay in larval development did not fully compensate for the earlier breeding, such that for every 2 days earlier that breeding took place, the average date of metamorphosis was 1 day earlier. Other studies have found that earlier metamorphosis is associated with increased postmetamorphic growth and survival, suggesting that earlier breeding has beneficial effects on wood frog populations.     

Climate change has affected the breeding date of tree swallows throughout North America

Increasing evidence suggests that climate change has affected the breeding and distribution of wildlife. If such changes are due to global warming, then we should expect to see large-scale effects. To explore for such effects on avian reproduction, we examined 3450 nest records of tree swallows from across North America. The egg-laying date in tree swallows advanced by up to nine days during 1959-1991. This advance in phenology was associated with increasing surface air temperatures at the time of breeding. Our analysis controlled for several potentially confounding variables such as latitude, longitude, breeding density and elevation. We conclude that tree swallows across North America are breeding earlier and that the most likely cause is a long-term increase in spring temperature.     

Breeding success at the range margin of a desert species: implications for a climate‐induced elevational shift

If the breeding range of a species is limited by biotic or abiotic environmental factors that depress breeding success at the range margin, then range expansion is expected when those limiting factors are alleviated. Over a three‐year period, we measured breeding success of a desert species, black‐throated sparrow Amphispiza bilineata, along a steep elevation gradient between the Peninsular Mountains and Colorado Desert (San Diego County, California) that is undergoing a warming trend. We compared breeding success at geographically marginal locations (higher‐elevation chaparral sites) to more central locations (lower‐elevation desert scrub sites) only a short distance apart. Breeding success was measured at the nest level, territory level, and population level. At each level measured, breeding success tended to be greater at higher‐elevation chaparral sites at the distribution margin compared to lower‐elevation sites where the bird was more common. Black‐throated sparrows had 100% reproductive failure at lower‐elevation sites during the two driest years of our study (2006–2007), but did relatively well at higher‐elevation sites. Only in a wetter year (2008) was breeding success improved at lower‐elevation sites. Surprisingly, there was no evidence of an upward elevational shift in distribution over a 26‐year period despite a clear warming trend and drier conditions. Greater territory density at lower‐elevation sites with reproductive failure during dry years suggests the possibility of an ecological trap in this system, which could prevent or delay climate‐induced range shifts. A common presumption has been that desert species will undergo relatively mild negative impacts due to a warming climate, but it is possible that some desert species are already at or near their temperature and aridity tolerance limits within their current range and shifts may not always be possible.     

Earlier breeding,lower success: does the spatial scale of climatic conditions matter in a migratory passerine bird?

Following over 20 years of research on the climatic effects on biodiversity we now have strong evidence that climate change affects phenology, fitness, and distribution ranges of different taxa, including birds. Bird phenology likely responds to changes in local weather. It is also affected by climatic year‐to‐year variations on larger scales. Although such scale‐related effects are common in ecology, most studies analyzing the effects of climate change were accomplished using climatic information on a single spatial scale. In this study, we aimed at determining the scale‐dependent sensitivity of breeding phenology and success to climate change in a migratory passerine bird, the barn swallow (Hirundo rustica). For both annual broods, we investigated effects of local weather (local scale) and the North Atlantic Oscillation (NAO, large scale) on the timing of breeding and breeding success. Consistent with previous studies in migratory birds we found that barn swallows in Eastern Germany bred progressively earlier. At the same time, they showed reduced breeding success over time in response to recent climatic changes. Responses to climatic variation were observed on both local and large climatic scales, but they differed with respect to the ecological process considered. Specifically, we found that the timing of breeding was primarily influenced by large‐scale NAO variations and to a lesser extent by local weather on the breeding grounds. Conversely, climatic conditions on the local scale affected breeding success, exclusively. The observed decrease in breeding success over years is likely a consequence of scale‐related mismatches between climatic conditions during different breeding phases. This provides further evidence that a species' response of earlier breeding may not be enough to cope with climate change. Our results emphasize the importance of considering the response of ecological processes along different climatic scales in order to better understand the complexity of climate change effects on biodiversity.     

Warm Springs,Early Lay Dates,and Double Brooding in a North American Migratory Songbird,the Black-Throated Blue Warbler

Numerous studies have correlated the advancement of lay date in birds with warming climate trends, yet the fitness effects associated with this phenological response have been examined in only a small number of species. Most of these species–primarily insectivorous cavity nesters in Europe–exhibit fitness declines associated with increasing asynchrony with prey. Here, we use 25 years of demographic data, collected from 1986 to 2010, to examine the effects of spring temperature on breeding initiation date, double brooding, and annual fecundity in a Nearctic - Neotropical migratory songbird, the black-throated blue warbler (Setophaga caerulescens). Data were collected from birds breeding at the Hubbard Brook Experimental Forest, New Hampshire, USA, where long-term trends toward warmer springs have been recorded. We found that black-throated blue warblers initiated breeding earlier in warmer springs, that early breeders were more likely to attempt a second brood than those starting later in the season, and that double brooding and lay date were linked to higher annual fecundity. Accordingly, we found selection favored earlier breeding in most years. However, in contrast to studies of several other long-distance migratory species in Europe, this selection pressure was not stronger in warmer springs, indicating that these warblers were able to adjust mean lay date appropriately to substantial inter-annual variation in spring temperature. Our results suggest that this North American migratory songbird might not experience the same fecundity declines as songbirds that are unable to adjust their timing of breeding in pace with spring temperatures.     

南盘江流域云南松径向生长对气候暖干化的响应

全球气候变暖背景下, 西南地区气候呈现出明显的暖干化特征, 但区域优势树种云南松(Pinus yunnanensis)对气候暖干化的响应存在不确定性。该研究根据树木年代学方法选择研究区域87株云南松样本进行树芯采集, 构建云南松树轮年表, 结合1952-2016年的气温和降水等气象资料, 利用响应分析、多元回归分析以及滑动相关分析等方法研究了影响南盘江流域云南松径向生长的关键气候因子及其对气候暖干化的响应规律。研究结果表明: 1985年以来, 研究区域气候暖干化特征明显, 气温上升和降水量下降的速率是1984年前的5和6倍, 年平均气温、年平均最高气温、年平均最低气温的上升速率为0.044、0.041和0.050 ℃·a ^-1, 年降水量的下降速率为 6.02 mm·a ^-1。气候暖干化使云南松的生长对温度响应的敏感度降低, 对水分响应的敏感度增强, 气温的解释率由暖干化前的44.95%下降到21.97%, 水分的解释率由暖干化前的55.05%上升到78.03%。暖干化增强了当年气候因子对径向生长的影响, 减弱了上年气候因子的影响, 与径向生长显著相关的当年气候因子增加了3个, 当年气候因子对径向生长的解释率增加了16.05%。暖干化减弱了云南松生长的“滞后效应”, 气候变化对树木生长影响的时效性增强。在5-7月和9-11月, 气候变暖使径向生长与气温、水分的响应关系变得不稳定。该研究可为气候暖干化区域云南松林的经营、管理以及区域气候重建提供理论依据和基础数据。     

Climate change and temperature-dependent sex determination: can individual plasticity in nesting phenology prevent extreme sex ratios?

Under temperature-dependent sex determination (TSD), temperatures experienced by embryos during development determine the sex of the offspring. Consequently, populations of organisms with TSD have the potential to be strongly impacted by climatic warming that could bias offspring sex ratio, a fundamental demographic parameter involved in population dynamics. Moreover, many taxa with TSD are imperiled, so research on this phenomenon, particularly long-term field study, has assumed great urgency. Recently, turtles with TSD have joined the diverse list of taxa that have demonstrated population-level changes in breeding phenology in response to recent climate change. This raises the possibility that any adverse impacts of climate change on populations may be alleviated by individual plasticity in nesting phenology. Here, we examine data from a long-term study on a population of painted turtles (Chrysemys picta) to determine whether changes in phenology are due to individual plasticity and whether individual plasticity in the timing of nesting has the capacity to offset the sex ratio effects of a rise in climatic temperature. We find that individual females show plasticity in the date of first nesting each year, and that this plasticity depends on the climate from the previous winter. First nesting date is not repeatable within individuals, suggesting that it would not respond to selection. Sex ratios of hatchlings within a nest declined nonsignificantly over the nesting season. However, small increases in summer temperature had a much stronger effect on nest sex ratios than did laying nests earlier in the season. For this and other reasons, it seems unlikely that individual plasticity in the timing of nesting will offset the effects of climate change on sex ratios in this population, and we hypothesize that this conclusion applies to other populations with TSD.     

Global warming and egg size of birds

Global warming or climate change is known to have many effects on plants, but there has been relatively little research on global warming and animals, partly because too few long-term studies have been carried out. In northern areas, mean temperature is believed to be rising, and indeed during the last decades mean spring temperatures in Finnish Lapland have increased. In 1975-1993, mean air temperature during the main egg-laying period of a pied flycatcher Ficedula hypoleuca population correlated positively and significantly with mean egg volume of that population. Since larger eggs enjoy improved hatching success, global warming may alter birds' reproductive strategies, because warmer weather may allow females to invest more resources in reproduction. This in turn may help birds rapidly conquer new areas when they become available and compensate for rising mortality rates to be expected elsewhere where warming means desiccation.     

Temperature during egg formation and the effect of climate warming on egg size in a small songbird

The predicted effects of recent climate warming on egg size in birds are controversial, as only two long-term studies have been reported, with contrasting results. Long-term data on egg size variation are analyzed in relation to ambient temperatures in a southern European population of pied flycatchers where breeding phenology has not matched the spring advancement in the last decades. Cross-sectional, population analyses indicated that egg breadth, but not egg length, has decreased significantly along the 16-year period, leading to marginally non-significant decreases in egg volume. Longitudinal, individual analyses revealed that despite females consistently laying larger eggs when they experienced warmer temperatures during the prelaying and laying periods, there was an overall negative response – i.e. decreasing egg volume and breadth with increasing spring (May) average temperatures – across individuals. This trend is hypothesised to be caused by the mismatched breeding phenology, in relation to climate warming, of this population. Except in the unlikely cases of populations capable of perfectly synchronising their phenology to changes in their environment, maladjustments are likely for traits such as egg size, which depend strongly on female condition. Slight changes or absence thereof in breeding dates may be followed by mismatched dates, in terms of food abundance, for optimal egg formation, which would be reflected in smaller average egg size, contrary to early predictions on the effects of climate warming on bird egg size.     

Climatic effects on arrival and laying dates in a long-distance migrant, the Collared Flycatcher Ficedula albicollis

Long‐distance migrants may respond to climate change in breeding, wintering or staging area by changing their phenology. The geographical variation in such responses (e.g. coastal vs. continental Europe) and the relative importance of climate at different spatial scales remain unclear. Here we analysed variation in first arrival dates (FADs) and laying dates of the Collared Flycatcher Ficedula albicollis in a central European population, from 1973 to 2002. The North Atlantic Oscillation (NAO) index correlated weakly with local temperature during the laying period. Decreasing spring temperatures until 1980 were associated with a trend towards later laying. The rate of warming (0.2 °C per year) and laying advancement (0.4 days per year) since 1980 are amongst the highest values reported elsewhere. This long‐term trend in laying date was largely explained by the change in climatic factors. The negative effect of local spring temperature on laying was relatively stronger than that of NAO. The number of clutches initiated on a particular day was marginally affected by the temperature 3 days prior to laying and the response of females to daily variation in temperature did not change over years. Correspondence between the average population‐level and the individual‐level responses of laying date to climate variation suggests that the advancement of laying was due to phenotypic plasticity. Despite warmer springs and advanced laying, FADs did not change over years and were not correlated with local spring temperature. Marginal evidence suggests later departure from wintering grounds and faster migration across staging areas in warmer conditions. Advancement of arrival was probably constrained by low local temperatures in early spring just before arrival that have not changed over years. The interval between first arrival and laying has declined since 1980 (0.5 days per year), but the increasing temperature during that period may have kept the food supply approximately unchanged.