Multi‐decadal trends in spring arrival of avian migrants to the central Arctic coast of Alaska: effects of environmental and ecological factors

Warming in the Arctic has caused the transition from winter to summer to occur weeks earlier over the last half century, yet little is known about whether avian migrants have altered their timing of arrival on breeding areas to match this earlier seasonal transition. Over a 50‐yr period, we examined trends in the timing of the first arrival for 16 avian migrant species at the terminus of their northward migration along the central Arctic coast of Alaska and compared these trends to factors potentially influencing migration phenology. Date of first arrival occurred an average of 0.12 d yr^?1 or 6 d (range = 3–10 d) earlier across all species and did not differ significantly among species between 1964 and 2013. Local climatic variables, particularly temperature, had a greater effect on a species first arrival date than did large‐scale climatic predictors. First arrival date was 1.03 d earlier for every 1°C annual change in temperature, but there was nearly a 2‐fold difference in the range of responses across species (0.69–1.33 d °C^?1), implying that some species did better than others at timing their arrival with changing temperature. There was weak support for an influence of foraging strategy, migration distance, and flight path on timing of first arrival. Our findings, like others from temperate latitudes, indicate that avian migrants are responsive to changing environmental conditions, though some species appear to be more adaptive than others.     

Light‐level geolocation reveals wintering distribution,migration routes,and primary stopover locations of an endangered long‐distance migratory songbird

The importance of understanding the geographic distribution of the full annual cycle of migratory birds has been increasingly highlighted over the past several decades. However, the difficulty of tracking small birds between breeding and wintering areas has hindered progress in this area. To learn more about Kirtland's warbler Setophaga kirtlandii movement patterns throughout the annual cycle, we deployed archival light‐level geolocators across their breeding range in Michigan. We recovered devices from 27 males and analyzed light‐level data within a Bayesian framework. We found that most males wintered in the central Bahamas and exhibited a loop migration pattern. In both fall and spring, departure date was the strongest predictor of arrival date, but in spring, stopover duration and migration distance were also important. Though stopover strategies varied, males spent the majority of their spring migration at stopover sites, several of which were located just before or after large ecological barriers. We argue that loop migration is likely a response to seasonal variation in prevailing winds. By documenting a tight link between spring departure and arrival dates, we provide a plausible mechanism for previously documented carry‐over effects of winter rainfall on reproductive success in this species. The migratory periods remain the least understood periods for all birds, but by describing Kirtland's warbler migration routes and timing, and identifying locations of stopover sites, we have begun the process of better understanding the dynamics of their full annual cycle. Moreover, we have provided managers with valuable information on which to base future conservation and research priorities.     

Temperature‐related increases in grass growth and greater competition for food drive earlier migrational departure of wintering Whooper Swans

Understanding the departure decisions of migratory birds is critical for determining how changing climatic conditions will influence subsequent arrival times on the breeding grounds. A long‐term dataset (1972–2008) of Whooper Swan Cygnus cygnus departure dates from a wintering site in Ireland was used to assess the factors determining the timing of migration. Early and late migrating swans showed different departure patterns. Earlier wintering ground departure was more pronounced for the first 50% of the population than the last 10% of departing individuals. Earlier departure was associated with an increase in February temperatures at the wintering site for all departure phases except the date when the last individual departed. The date by which the first 50% of Swans had departed was earlier with increasing numbers of wintering Swans, suggesting that competition on the wintering grounds may further influence the timing of departure. The results also suggested that departure is mediated by the influence of spring temperature on food resources, with increased February grass growth in warmer years enabling earlier departure of migrating Swans. To determine why arrival dates in the breeding ground have altered, environmental conditions in the wintering grounds must be taken into account.     

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 effects of climate change on the phenology of winter birds in Yokohama, Japan

Observations made largely from summer breeding sites in Europe and North America have been used to document the effects of climate change on many bird species. We extend these studies by examining 23 years of observations between 1986 and 2008 of six winter bird species made by citizens at a city park in Yokohama, Japan. Bird species arrive in autumn and spend the winter in the area, before departing in the late winter or spring. On average, birds species are arriving 9 days later than in the past and are departing on average 21 days earlier, meaning that the average duration of their stay in Yokohama is about 1 month shorter now than in the past. Patterns of changes over time varied among species, but departure dates changed for more species than did arrival dates. Dates of departure and arrival were sometimes correlated with monthly average temperatures—later arrivals and earlier departures were associated with warmer temperatures. In addition, interannual variation in arrival and departure dates were strongly correlated across species, suggesting that species were responding to the same or similar environmental cues. This study provides a clear demonstration of the value of using citizens to make observations that contribute to research in climate change biology.     

The influence of snow on the functional response of grazing ungulates

The forage intake rate of grazing ungulates is limited either by the rate at which they encounter food items, or the rate at which food items are handled. Whether an ungulate is encounter‐ or handling‐limited influences spatial and temporal depletion of forage, daily time budgets, and ultimately animal condition. Previously, vegetation abundance has been used as a surrogate for an ungulate's encounter rate with food items and related to observed bite rate to determine whether intake rate is encounter‐ or handling‐limited. In temperate climates snow accumulation during winter limits access to vegetation by forcing animals to wade and paw through snow to consume underlying vegetation, increasing the amount of time required to encounter a food item. As a result, an ungulate may be handling‐limited when foraging in a high biomass system under snow‐free conditions, but becomes encounter‐limited when snow accumulates. We derived a model that provides a frame work for estimating the rate at which a grazing ungulate encounters vegetation by considering foraging velocity, vegetation biomass and the time required to paw away snow when present. We then used data from focal observations of 36 wild elk Cervus canadensis wintering on a montane grassland in the Canadian Rockies of Alberta, Canada, to apply our model and estimate encounter rate over a range of vegetation abundance and snow conditions. Using AIC_c in a model selection approach we found that an asymptotic regression model of observed bite rate as a function of estimated encounter rate provided a better fit than similar models using only vegetation abundance as the explanatory variable. An asymptotic model suggests elk were handling‐limited in the absence of snow, but became encounter‐limited when snow accumulated. Our results demonstrate the importance of considering the influence of factors other than vegetation abundance on the intake rate of grazing ungulates.     

The impact of snow accumulation on a heath spider community in a sub-Arctic landscape

Patterns of snow cover across the Arctic are expected to change as a result of shrub encroachment and climate change. As snow cover impacts both the subnivean environment and the date of spring melt, these changes could impact Arctic food webs by altering the phenology and survival of overwintering arthropods, such as spiders (Araneae). In this field study, we used snow fences to increase snow cover across a series of large (375 m²) heath tundra plots and examined the effects on the local spider community during the following growing season. Fences increased snow cover and delayed melt on the treatment plots, paralleling the conditions of nearby shrub sites. Frequent sampling over the season revealed that increased snow cover did not affect spider abundance across different genera nor did it affect overall community composition. Further, our snow treatment did not affect the dates when plots achieved seasonal catch milestones (25, 50, 75 % of total seasonal catch). Increased winter snow cover did, however, produce higher body masses in adults and juveniles of the dominant species Pardosa lapponica (Lycosidae), beginning immediately after snow melt until midway through the growing season. In addition, ovary/oocyte mass of mature P. lapponica females was significantly higher on treatment plots during the peak reproductive period. This is the first experimental manipulation study to report a significant effect of landscape-level changes to winter snow cover on the biomass of an Arctic macroarthropod.     

Migration phenology and winter habitat quality are related to circulating androgen in a long‐distance migratory bird

In migratory birds, the timing of departure from wintering grounds is often dependant on the quality of habitat on an individual's territory and may influence individual fitness, resulting in an interaction of life history stages across large geographical distances. American redstart Setophaga ruticilla males who overwinter in high quality habitats arrive early to breed and subsequently produce more offspring than late arrivers. Since many migratory species overlap vernal migration with the physiological transition to breeding, we examined if breeding preparation plays a role in this seasonal interaction. We tested the hypothesis that early arriving male redstarts from high quality winter habitats are in superior breeding condition by simultaneously measuring winter habitat quality (stable‐carbon isotopes) and breeding preparation (circulating androgen, cloacal protuberance (CP) diameter) upon arrival at breeding grounds. Compared with late arrivers, early arriving males were from higher quality winter habitats and had higher androgen, but smaller CPs. Males arriving with higher androgen were in more advanced physiological migratory condition, as measured by haematocrit. Early arrivers were more likely to successfully breed, but there was no significant relationship between androgen upon arrival and breeding success. One possible explanation for these relationships is that androgen measured during arrival is most relevant in a migratory context, such that birds with high androgen may benefit from effects on migratory condition, positively influencing fitness through earlier arrival.     

Overtaking on migration: does longer distance migration always incur a penalty?

For many migratory bird species, the latitudinal range of the winter distribution spans thousands of kilometres, thus encompassing considerable variation in individual migration distances. Pressure to winter near breeding areas is thought to be a strong driver of the evolution of migration patterns, as individuals undertaking a shorter migration are generally considered to benefit from earlier arrival on the breeding grounds. However, the influence of migration distance on timing of arrival is difficult to quantify because of the large scales over which individuals must be tracked. Using a unique dataset of individually‐marked Icelandic black‐tailed godwits Limosa limosa islandica tracked throughout the migratory range by a network of hundreds of volunteer observers, we quantify the consequences of migrating different distances for the use of stop‐over sites and timing of arrival in Iceland. Modelling of potential flight distances and tracking of individuals from across the winter range shows that individuals wintering further from the breeding grounds must undertake a stop‐over during spring migration. However, despite travelling twice the distance and undertaking a stop‐over, individuals wintering furthest from the breeding grounds are able to overtake their conspecifics on spring migration and arrive earlier in Iceland. Wintering further from the breeding grounds can therefore be advantageous in migratory species, even when this requires the use of stop‐over sites which lengthen the migratory journey. As early arrival on breeding sites confers advantages for breeding success, the capacity of longer distance migrants to overtake conspecifics is likely to influence the fitness consequences of individual migration strategies. Variation in the quality of wintering and stopover sites throughout the range can therefore outweigh the benefits of wintering close to the breeding grounds, and may be a primary driver of the evolution of specific migration routes and patterns.     

Spring arrival response to climate change in birds: a case study from eastern Europe

This paper analyses the dependence of the first spring arrival dates of short/medium- and long-distance migrant bird species on climate warming in eastern Europe. The timing of arrival of the selected species at the observation site correlates with the North Atlantic Oscillation (NAO) index, air temperature, atmospheric pressure, precipitation and wind characteristics. A positive correlation of fluctuations in winter and spring air temperatures with variations in the NAO index has been established in eastern Europe. Positive winter NAO index values are related to earlier spring arrival of birds in the eastern Baltic region and vice versa—arrival is late when the NAO index is negative. The impact of climate warming on the bird’s life cycle depends on local or regional climate characteristics. We tested the hypothesis that differences in climate indices between North Africa and Europe can influence the timing of spring arrival. Our results support the hypothesis that differences in first spring arrival dates between European populations occur after individuals cross the Sahara. We assume that the endogenous programme of migration control in short/medium-distance migrants synchronises with the changing environment on their wintering grounds and along their migration routes, whereas in long-distance migrants it is rather with environmental changes in the second part of their migratory route in Europe. Our results strongly indicate that the mechanism of dynamic balance in the interaction between the endogenous regulatory programme and environmental factors determines the pattern of spring arrival, as well as migration timing.     

Weather-related mass-mortality events in migrants

A major perceived cost of migration in birds is the associated mortality. This mortality has proved difficult to measure and separate from mortality during stationary periods of the annual cycle. This paper reviews some major recorded mortality incidents among migratory birds attributed to inclement weather and other factors, including: (1) in‐flight losses, caused by storms and other adverse weather en route, usually over water; (2) unseasonable cold weather soon after arrival in breeding areas; and (3) unseasonable cold weather before departure from breeding areas. Cold weather often kills migrants in their breeding areas, but not the local resident species which can better withstand it at those times. For migrants, cold and snow act to cut off the food supply, and can have a major selective effect on the seasonal timing of migration. Records of in‐flight weather‐induced mortality, involving up to hundreds or thousands of birds at a time, have affected mainly small passerines, but also larger birds, including eagles and swans. Most occurred in conditions of mist, rain or snow storms, and some involved nocturnal collisions with illuminated masts and other tall structures. Records of post‐arrival mortality in breeding areas have involved mainly small insectivores (especially hirundines), but also waders and waterfowl. Such incidents, associated with cold and snow, have reduced local breeding densities from the previous year by 25–90%, depending on species and area, with up to several years required for recovery. Records of pre‐departure mortality on breeding areas have mainly affected hirundines. Two major incidents in central Europe in September 1931 and 1974 killed hundreds of thousands, or even millions, of swallows and martins. After the latter incident, House Martin Delichon urbicum populations in Switzerland the following year were reduced by an estimated 25–30%. Such climatic extremes that occurred in spring or late summer in particular parts of the breeding range have been recorded at approximate mean frequencies of 2–10 per century. Average daily mortality in many bird species can clearly be much greater during migration periods than during stationary periods. Despite the heavy losses of birds on migration, it may be assumed that migration persists in the long term because the fitness costs (in terms of associated mortality) are more than offset by the fitness benefits (in terms of improved overall survival and breeding success) that accrue from migration.     

Demographic responses to a mild winter in enclosed vole populations

Mild winter weather causing snow to melt and ice to accumulate on the ground has been proposed to cause the decreased survival of individuals, and less pronounced cyclicity, of small rodent populations in Fennoscandia. However, detailed data linking ice accumulation to decreased winter survival is lacking. We live-trapped and monitored with passive integrated transponders enclosed populations of root voles (Microtus oeconomus) exposed to different amounts of ice accumulation through a mild winter. We studied how social behaviour and survival responded to snow melt and ice accumulation. Voles avoided ground ice by moving their home ranges, thus increasing home range overlap in enclosed populations experiencing more extensive ice cover. Winter survival was not affected by the amount of ice accumulation, and was only slightly reduced during ice formation in early winter. The lowest survival rates were found at the onset of snow melt in early spring. These results suggest that ice accumulation does not cause lower survival during mild winters, probably because plastic social behaviour enables root voles to reduce the negative effects of varying winter weather on survival. The mechanisms for lower survival during mild winters may operate during spring and be related to spring floods or increased susceptibility to predators. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Quantifying non‐breeding season occupancy patterns and the timing and drivers of autumn migration for a migratory songbird using Doppler radar

For seasonal migrants, non‐breeding regions can play different roles in the ecology of their annual cycles: as stopover habitat, overwintering habitat, or as a combination in which some individuals stop‐over and others over‐winter. Such functional variations can lead to variation in occupancy dynamics and migration phenology to these different regions. In this study, we used data from archived Doppler weather surveillance radar to compare site‐occupancy and movement dynamics of a migratory songbird (tree swallow Tachycineta bicolor) between two non‐breeding areas: southeastern Louisiana and central peninsular Florida, USA. Specifically, in each area, we 1) quantified long‐term (1996–2012) non‐breeding season occupancy dynamics, 2) quantified variation in timing of autumn migration, and 3) tested which climate variables along their respective flyways were best correlated with variation in dates of arrival. Additionally, we cross‐validated the dynamics from archived radar with data from eBird, a large‐scale citizen science database that provides an independent measure of avian occupancy. We found strong and significant correlations between radar‐estimated and eBird‐estimated occupancy dynamics in both Louisiana and Florida. Long‐term Louisiana occupancy dynamics conformed to our hypothesis that this region acts as a combined stopover and overwintering region whereas Florida occupancy dynamics were akin to a traditional winter region. Arrival to Louisiana during the study period was much earlier and took place over a much shorter arrival window than did arrival to Florida, which showed much more gradual arrival over the course of several months. At both sites, annual variation in mean arrival date was best explained by the amount of precipitation along the lower portions of their respective migration flyways.     

Effect of global warming on the timing of migration and breeding of passerine birds in the 20th century

Long-term monitoring of the dates of arrival, breeding, and autumn migration in 25 passerine bird species on the Kurshskaya (Courland) Spit, the Baltic Sea, has shown that spring migration and nesting in most species wintering in Europe or Africa have shifted to earlier dates in the past two decades, whereas the dates of autumn migration in most species studied have not changed significantly. In 16 bird species, a significant negative correlation of the timing of arrival and breeding with the average spring air temperature and the North Atlantic Oscillation index (NAO) in February and March was revealed. In years with early and warm springs, birds arrived at the spit and nested considerably earlier than in years with cold springs. The dates of autumn migration in most species studied largely depended on the timing of nesting but not on weather conditions in autumn. The data obtained indicate that the main factor responsible for long-term changes in the timing of arrival, nesting, and autumn migrations of passerine birds in the Baltic Region is climate fluctuations that led to considerable changes in thermal conditions in the Northern Hemisphere in the 20th century. The hypothesis is proposed that recent climate warming has caused changes in the timing of not only the arrival of birds in Europe but also of their spring migrations from Africa. Further changes in the dates of passerine bird arrival and breeding in the Palearctic in subsequent years will largely depend on the dynamics of winter and spring air temperatures in the Northern Hemisphere, whereas the timing of autumn migrations will be determined mainly by the dates of their arrival and nesting.     

Examining the total arrival distribution of migratory birds

This paper reports on the total distribution of spring migration timing of willow warbler, chiffchaff and pied flycatcher at locations in the UK, Germany, Russia and Finland. This is the first time that high‐quality data based on known‐effort monitoring has been examined on a continental scale. First arrival dates, commonly reported in the literature, were positively correlated with mean arrival dates although they would not make good predictors of the latter. At all locations, at least one aspect of the arrival distribution of each species had got significantly earlier in recent years. The trend towards earliness was associated with warmer local temperatures and more positive winter North Atlantic Oscillation index. In years that were early, the arrival distribution became more elongated and skewed. Researchers should now investigate the consequences of earlier arrival on current and future bird populations.     

Winter rainfall predicts phenology in widely separated populations of a migrant songbird

Climate change is affecting behaviour and phenology in many animals. In migratory birds, weather patterns both at breeding and at non-breeding sites can influence the timing of spring migration and breeding. However, variation in responses to weather across a species range has rarely been studied, particularly among populations that may winter in different locations. We used prior knowledge of migratory connectivity to test the influence of weather from predicted non-breeding sites on bird phenology in two breeding populations of a long-distance migratory bird species separated by 3,000 km. We found that winter rainfall showed similar associations with arrival and egg-laying dates in separate breeding populations on an east–west axis: greater rainfall in Jamaica and eastern Mexico was generally associated with advanced American redstart (Setophaga ruticilla) phenology in Ontario and Alberta, respectively. In Ontario, these patterns of response could largely be explained by changes in the behaviour of individual birds, i.e., phenotypic plasticity. By explicitly incorporating migratory connectivity into responses to climate, our data suggest that widely separated breeding populations can show independent and geographically specific associations with changing weather conditions. The tendency of individuals to delay migration and breeding following dry winters could result in population declines due to predicted drying trends in tropical areas and the tight linkage between early arrival/breeding and reproductive success in long-distance migrants.     

Relating the movement of a rapidly migrating ungulate to spatiotemporal patterns of forage quality

Migratory ungulates exhibit recurring movements, often along traditional routes between seasonal ranges each spring and autumn, which allow them to track resources as they become available on the landscape. We examined the relationship between spring migration of mule deer (Odocoileus hemionus) and forage quality, as indexed by spatiotemporal patterns of fecal nitrogen and remotely sensed greenness of vegetation (Normalized Difference Vegetation Index; NDVI) in spring 2010 in the Piceance Basin of northwestern Colorado, USA. NDVI increased throughout spring, and was affected primarily by snow depth when snow was present, and temperature when snow was absent. Fecal nitrogen was lowest when deer were on winter range before migration, increased rapidly to an asymptote during migration, and remained relatively high when deer reached summer range. Values of fecal nitrogen corresponded with increasing NDVI during migration. Spring migration for mule deer provided a way for these large mammals to increase access to a high-quality diet, which was evident in patterns of NDVI and fecal nitrogen. Moreover, these deer “jumped” rather than “surfed” the green wave by arriving on summer range well before peak productivity of forage occurred. This rapid migration may aid in securing resources and seclusion from others on summer range in preparation for parturition, and to minimize detrimental factors such as predation, and malnutrition during migration.     

Ecological conditions in wintering and passage areas as determinants of timing of spring migration in trans-Saharan migratory birds

1.?Climate change has been associated with shifts in the timing of biological events, including the spring arrival of migratory birds. Early arrival at breeding sites is an important life-history trait, usually associated with higher breeding success and therefore, susceptible to selection and evolution in response to changing climatic conditions. 2.?Here, we examine the effect of changes in the environmental conditions of wintering and passage areas on the mean passage time of 13 trans-Saharan passerines during their spring migration through the western Mediterranean over the 15 years from 1993 to 2007. 3.?We found that most of the species studied have been advancing the timing of their passage in recent years. However, annual variation in the mean date of passage was positively correlated with vegetation growth (measured as the normalized difference vegetation index [NDVI]) both in the Sahel (the region of departure) and in northern Africa (the passage area). Thus, migration dates were delayed in years with high primary productivity in passage and wintering zones. All species seem to respond similarly to NDVI in the Sahel; however, late migrants were less affected by ecological conditions in northern Africa than those migrating earlier, suggesting differences based on species ecology. 4.?Mean timing of passage was not related to the North Atlantic Oscillation (NAO), El Ni?o-Southern Oscillation (ENSO), temperature or NDVI in the species-specific wintering areas (the overwintering region) when analysed in combination with the other covariates. 5.?Our findings show that ecological conditions in the winter quarters (specifically the Sahel) and en route are relevant factors influencing trends in the passage dates of trans-Saharan migratory birds on the southern fringe of Europe. Possible long-term consequences for late arriving spring migrants are discussed.     

Autumn resource selection by female elk in a recently burned landscape in western Montana

Wildfire activity across the western United States has increased in recent decades, with wildfires burning at a higher severity and larger scale. The effect of wildfires on forest structure and wildlife habitat is largely influenced by wildfire severity; however, few studies have evaluated the effects of wildfire severity on resource selection of ungulates, particularly during hunting seasons, when knowledge of resource selection is essential for making informed management decisions. To fill this knowledge gap, we fit resource selection probability functions for female elk (Cervus canadensis) in years 2 and 3 post-wildfire to evaluate the effects of wildfire severity and other environmental and anthropogenic factors on elk resource selection during 4 autumn periods with varying levels of hunter pressure (prehunt, archery-only, backcountry rifle, and rifle). The probability of female elk selecting low-severity burned forests during the prehunt, archery-only, backcountry rifle, and rifle periods was 0.99 (95% credible interval [CrI] = 0.98–1.00), 0.99 (CrI = 0.97–1.00), 0.99 (CrI = 0.99–1.00), and 0.0010 (CrI = 0.00067–0.0015]), respectively, and did not strongly differ from the probability of selecting high-severity burned forests. During the prehunt period, elk also selected areas with greater forage quality and areas farther from open roads. Elk selected similar resources during the archery period, and selected areas with higher hunter pressure. Elk started leaving hunting districts that had higher snowpack (i.e., snow water equivalent; β = −0.84, CrI = −0.96–−0.72) and allowed rifle hunting (β = −5.39, CrI = −5.80–−4.97) but still selected areas with higher hunter pressure (β = 0.92, CrI = 0.78–1.07) during the backcountry rifle period. During the rifle period, elk continued avoiding areas with high snowpack (β = −3.96, CrI = −4.22–−3.71) and started selecting areas with lower hunter pressure (β = −1.71, CrI = −1.79–−1.64) and lower canopy cover. Overall, wildfire affected elk distributions in early autumn 2 and 3 years after fire in our study area, with limited differences in resource selection between wildfire severity categories. By late autumn, hunter pressure and snowpack were the primary factors influencing elk distribution, and wildfire had little influence on selection. When estimating wildfire effects on elk movements during autumn and establishing appropriate hunting regulations, managers should consider the hunting season, hunter pressure, timing and amount of snowpack, location of traditional winter range, and the seasonal elk range burned, as all these factors may contribute to how elk use the landscape in autumn.     

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.