A temporally explicit species distribution model for a long distance avian migrant,the common cuckoo

Modelling the distribution of migratory species has rarely been extended beyond breeding and wintering ranges despite many species showing much more complex movement patterns with multiple stopovers. We aimed to create a temporally explicit species distribution model describing the full annual distribution cycle, and use it to model the complex seasonal shifts in distribution of the common cuckoo Cuculus canorus, a declining long‐distance migrant. To do this we used full‐year satellite telemetry occurrence data, with their associated temporal information, to inform a temporally explicit species distribution model using MaxEnt. The resulting full‐year distribution model was highly predictive (AUC = 0.894) and appeared to have generality at the species‐level despite being informed by data from a single breeding population. Comparison of our methodology with seasonal distribution models describing the breeding, winter and migration ranges separately showed that our full‐year method provided more general and extensive predictions and performed better when tested with an independent dataset. When species distribution models based on a single season exclude environmental conditions experienced by birds in other parts of the annual cycle they risk underestimating niche breadth and neglecting the importance of stopover habitat. Conversely, models which simply average conditions across a season may miss the significance of finer scale within‐season movements and overestimate niche breadth. In contrast, our framework for a full‐year migrant distribution model successfully captures the finer‐scale changes expected in seasonal environments and can be used to inform conservation management at every stage of migration. The full‐year model framework appears to produce temporal distribution models generalised to the species‐level from occurrence data limited to few individuals of a single population and may have particular utility when aiming to describe the distribution of species with complex migration patterns from telemetry data.     

Linking the continental migratory cycle of the monarch butterfly to understand its population decline

Threats to several of the world's great animal migrations necessitate a research agenda focused on identifying drivers of their population dynamics. The monarch butterfly is an iconic species whose continental migratory population in eastern North America has been declining precipitously. Recent analyses have linked the monarch decline to reduced abundance of milkweed host plants in the USA caused by increased use of genetically modified herbicide‐resistant crops. To identify the most sensitive stages in the monarch's annual multi‐generational migration, and to test the milkweed limitation hypothesis, we analyzed 22 years of citizen science records from four monitoring programs across North America. We analyzed the relationships between butterfly population indices at successive stages of the annual migratory cycle to assess demographic connections and to address the roles of migrant population size versus temporal trends that reflect changes in habitat or resource quality. We find a sharp annual population decline in the first breeding generation in the southern USA, driven by the progressively smaller numbers of spring migrants from the overwintering grounds in Mexico. Monarch populations then build regionally during the summer generations. Contrary to the milkweed limitation hypothesis, we did not find statistically significant temporal trends in stage‐to‐stage population relationships in the mid‐western or northeastern USA. In contrast, there are statistically significant negative temporal trends at the overwintering grounds in Mexico, suggesting that monarch success during the fall migration and re‐establishment strongly contributes to the butterfly decline. Lack of milkweed, the only host plant for monarch butterfly caterpillars, is unlikely to be driving the monarch's population decline. Conservation efforts therefore require additional focus on the later phases in the monarch's annual migratory cycle. We hypothesize that lack of nectar sources, habitat fragmentation, continued degradation at the overwintering sites, or other threats to successful fall migration are critical limiting factors for declining monarchs.     

Equal nonbreeding period survival in adults and juveniles of a long‐distant migrant bird

In migrant birds, survival estimates for the different life‐history stages between fledging and first breeding are scarce. First‐year survival is shown to be strongly reduced compared with annual survival of adult birds. However, it remains unclear whether the main bottleneck in juvenile long‐distant migrants occurs in the postfledging period within the breeding ranges or en route. Quantifying survival rates during different life‐history stages and during different periods of the migration cycle is crucial to understand forces driving the evolution of optimal life histories in migrant birds. Here, we estimate survival rates of adult and juvenile barn swallows (Hirundo rustica L.) in the breeding and nonbreeding areas using a population model integrating survival estimates in the breeding ranges based on a large radio‐telemetry data set and published estimates of demographic parameters from large‐scale population‐monitoring projects across Switzerland. Input parameters included the country‐wide population trend, annual productivity estimates of the double‐brooded species, and year‐to‐year survival corrected for breeding dispersal. Juvenile survival in the 3‐week postfledging period was low (S = 0.32; SE = 0.05), whereas in the rest of the annual cycle survival estimates of adults and juveniles were similarly high (S > 0.957). Thus, the postfledging period was the main survival bottleneck, revealing the striking result that nonbreeding period mortality (including migration) is not higher for juveniles than for adult birds. Therefore, focusing future research on sources of variation in postfledging mortality can provide new insights into determinants of population dynamics and life‐history evolution of migrant birds.     

Conditions at the breeding grounds and migration strategy shape different moult patterns of two populations of Eurasian golden plover Pluvialis apricaria

Events in the life cycle of migrant birds are generally time‐constrained. Moult, together with breeding and migration, is the most energetically demanding annual cycle stages, but it is the only stage that can be scheduled at different times of the year. However, it is still not fully understood what factors determine this scheduling. We compare the timing of primary feather moult in relation to breeding and migration between two populations of Eurasian golden plover Pluvialis apricaria, the continental population breeding in Scandinavia and in N Russia that migrates to the Netherlands and southern Europe, and the Icelandic population that migrates mainly to Ireland and western UK. Moult was studied at the breeding grounds (N Sweden, N Russia, Iceland) and at stopover and wintering sites (S Sweden, the Netherlands). In both populations, primary moult overlapped with incubation and chick rearing, and females started on average 9 d later than males. Icelandic plovers overlapped moult with incubation to a larger extent and stayed in the breeding grounds until primary moult was completed. In contrast, continental birds only moulted the first 5–7 primaries at the breeding grounds and completed moult in stopover and wintering areas, such as S Sweden and the Netherlands. This overlap, although rare in birds, can be understood from an annual cycle perspective. Icelandic plovers presumably need to initiate moult early in the season to be able to complete it at the breeding grounds. The latter is not possible for continental plovers as their breeding season is much shorter due to a harsher climate. Additionally, for this population, moulting all the primaries at the stopover/wintering site is also not possible as too little time would remain to prepare for cold‐spell movements. We conclude that environmental conditions and migration strategy affect the annual scheduling of primary feather moult in the Eurasian golden plover.     

Wind Speed during Migration Influences the Survival,Timing of Breeding,and Productivity of a Neotropical Migrant,Setophaga petechia

Over the course of the annual cycle, migratory bird populations can be impacted by environmental conditions in regions separated by thousands of kilometers. We examine how climatic conditions during discrete periods of the annual cycle influence the demography of a nearctic-neotropical migrant population of yellow warblers (Setophaga petechia), that breed in western Canada and overwinter in Mexico. We demonstrate that wind conditions during spring migration are the best predictor of apparent annual adult survival, male arrival date, female clutch initiation date and, via these timing effects, annual productivity. We find little evidence that conditions during the wintering period influence breeding phenology and apparent annual survival. Our study emphasizes the importance of climatic conditions experienced by migrants during the migratory period and indicates that geography may play a role in which period most strongly impacts migrant populations.     

Breeding latitude leads to different temporal but not spatial organization of the annual cycle in a long‐distance migrant

The temporal and spatial organization of the annual cycle according to local conditions is of crucial importance for individuals’ fitness. Moreover, which sites and when particular sites are used can have profound consequences especially for migratory animals, because the two factors shape interactions within and between populations, as well as between animal and the environment. Here, we compare spatial and temporal patterns of two latitudinally separated breeding populations of a trans‐Equatorial passerine migrant, the collared flycatcher Ficedula albicollis, throughout the annual cycle. We found that migration routes and non‐breeding residency areas of the two populations largely overlapped. Due to climatic constraints, however, the onset of breeding in the northern population was approximately two weeks later than that of the southern population. We demonstrate that this temporal offset between the populations carries‐over from breeding to the entire annual cycle. The northern population was consistently later in timing of all subsequent annual events – autumn migration, non‐breeding residence period, spring migration and the following breeding. Such year‐round spatiotemporal patterns suggest that annual schedules are endogenously controlled with breeding latitude as the decisive element pre‐determining the timing of annual events in our study populations.     

Spring phenology and timing of breeding in short‐distance migrant birds: phenotypic responses and offspring recruitment patterns in common goldeneyes

Understanding how organisms adjust breeding dates to exploit resources that affect fitness can provide insights into impacts of climate change on avian demography. For instance, mismatches have been reported in long‐distance migrant bird species when environmental cues experienced during spring migration are decoupled from conditions on breeding grounds. Short‐distance migrant bird species that store reproductive nutrients prior to breeding may avoid or buffer adverse phenological effects. Furthermore, reduced short‐term reproductive success could be offset by higher future recruitment of surviving offspring. We evaluated whether recruitment of locally‐hatched female offspring was related to hatching date alone or strength of mismatched breeding date for 405 individually‐marked adult female common goldeneyes Bucephala clangula (a short‐distance migrant) and their ducklings from a site in central Finland where ice‐out date has advanced by ～ 2 weeks over 24 yr. Path analyses revealed that older, early‐nesting females with good body condition and larger broods recruited the most female offspring. Offspring recruitment decreased strongly among females that bred late relative to other females in the population each year; the extent of mismatched breeding date, i.e. hatching date scaled to annual ice‐out date, was less influential. Overall, most females advanced breeding dates when ice‐out occurred earlier in spring, but some females exhibited greater flexibility in response to ice‐out conditions than did others. In general, directional selection favoured early breeding over a wide range of ice‐out dates. Our results seem most consistent with a hypothesis that some short‐distance migrant species like goldeneyes have the capacity to track and respond appropriately to changing environmental conditions prior to onset of breeding.     

Carry‐over effects and compensation: late arrival on non‐breeding grounds affects wing moult but not plumage or schedules of departing bar‐tailed godwits Limosa lapponica baueri

In the annual cycle of migratory birds, temporal and energetic constraints can lead to carry‐over effects, in which performance in one life history stage affects later stages. Bar‐tailed godwits Limosa lapponica baueri, which achieve remarkably high pre‐migratory fuel loads, undertake the longest non‐stop migratory flights yet recorded, and breed during brief high‐latitude summers, may be particularly vulnerable to persistent effects of disruptions to their rigidly‐timed annual routines. Using three years of non‐breeding data in New Zealand, we asked how arrival timing after a non‐stop flight from Alaska (>11 000 km) affected an individual godwit's performance in subsequent flight feather moult, contour feather moults, and migratory departure. Late arrival led to later wing moult, but godwits partially compensated for delayed moult initiation by increasing moult rate and decreasing the total duration of moult. Delays in arrival and wing moult up to 34–37 d had no apparent effect on an individual's migratory departure or extent of breeding plumage at departure, both of which were extraordinarily consistent between years. Thus, ‘errors’ in timing early in the non‐breeding season were essentially corrected in New Zealand prior to spring migration. Variation in migration timing also had no apparent effect on an individual's likelihood of returning the following season. The bar‐tailed godwits’ rigid maintenance of plumage and spring migration schedules, coupled with high annual survival, imply a surprising degree of flexibility to address unforeseen circumstances in the annual cycle.     

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.

     

Understanding population change in migratory songbirds: long‐term and experimental studies of Neotropical migrants in breeding and wintering areas

Effective conservation and management of migratory bird species requires an understanding of when and how their populations are limited and regulated. Since 1969, my colleagues and I have been studying migratory songbird populations in their breeding quarters at the Hubbard Brook Experimental Forest in north‐central New Hampshire, USA, and since 1986, in their winter quarters in the Greater Antilles (Jamaica). Long‐term data on the abundance and demography of these populations, coupled with experimental tests of mechanisms, indicate that processes operating in the breeding area (e.g. density‐dependent fecundity, food limitation) are sufficient to limit and regulate the local abundance of these species. At the same time, limiting factors operating in the non‐breeding season (e.g. climate‐induced food limitation in winter quarters and especially mortality during migration) also have important impacts on migrant populations. Furthermore, recent studies have shown that limiting processes during the winter period can carry over into the breeding season and affect reproductive output. These findings clearly demonstrate that to understand changes in abundance of long‐distance migrant species requires knowledge of events operating throughout the annual cycle, which presents a challenge to researchers, managers and others concerned with the welfare of these species.     

Climate change leads to differential shifts in the timing of annual cycle stages in a migratory bird

Shifts in reproductive phenology due to climate change have been well documented in many species but how, within the same species, other annual cycle stages (e.g. moult, migration) shift relative to the timing of breeding has rarely been studied. When stages shift at different rates, the interval between stages may change resulting in overlaps, and as each stage is energetically demanding, these overlaps may have negative fitness consequences. We used long‐term data of a population of European pied flycatchers (Ficedula hypoleuca) to investigate phenological shifts in three annual cycle stages: spring migration (arrival dates), breeding (egg‐laying and hatching dates) and the onset of postbreeding moult. We found different advancements in the timing of breeding compared with moult (moult advances faster) and no advancement in arrival dates. To understand these differential shifts, we explored which temperatures best explain the year‐to‐year variation in the timing of these stages, and show that they respond differently to temperature increases in the Netherlands, causing the intervals between arrival and breeding and between breeding and moult to decrease. Next, we tested the fitness consequences of these shortened intervals. We found no effect on clutch size, but the probability of a fledged chick to recruit increased with a shorter arrival‐breeding interval (earlier breeding). Finally, mark–recapture analyses did not detect an effect of shortened intervals on adult survival. Our results suggest that the advancement of breeding allows more time for fledgling development, increasing their probability to recruit. This may incur costs to other parts of the annual cycle, but, despite the shorter intervals, there was no effect on adult survival. Our results show that to fully understand the consequences of climate change, it is necessary to look carefully at different annual cycle stages, especially for organisms with complex cycles, such as migratory birds.     

‘Same procedure as last year?‘ Repeatedly tracked swifts show individual consistency in migration pattern in successive years

Individual migration pattern during non‐breeding season is still a black box in many migratory birds. However, knowledge on both individual level and population level in migration and overwintering is fundamental to understand the life cycle of these birds and the constraints affecting them. We showed in a highly aerial migrant, the common swift Apus apus, that repeatedly tracked birds breeding at one site in Germany used the same individual‐specific migration routes and wintering areas in subsequent years. In contrast, different individuals from the same breeding colony showed diverse movement patterns during non‐breeding season suggesting that several suitable areas for overwintering coexist. We found lower variation in timing of autumn and spring migration within than between individuals. Our findings provide first indication of individual consistency but between‐individual variation in migration pattern in a small non‐passerine bird revealed by geolocators. This supports that swifts have diverse but individual‐specific ‘step‐by‐step’ migration patterns revealing high flexibility through individual strategies.     

Individual consistency of long‐distance migration in a songbird: significant repeatability of autumn route,stopovers and wintering sites but not in timing of migration

Through new tracking techniques, data on timing and routes of migration in long‐distance migrant birds are accumulating. However, studies of the consistency of migration of the same individuals between years are still rare in small‐sized passerine birds. This type of information is important to understand decisions and migration abilities at the individual level, but also for life history theory, for understanding carry over effects between different annual cycle stages and for conservation. We analysed individual repeatability of migration between years in great reed warblers Acrocephalus arundinaceus; a medium‐sized European songbird migrating to sub‐Saharan Africa. In seven males, with geolocator data from 2–4 yr per bird, we found low to moderate (non significant) repeatability in timing of migration parameters (R ≤ 0.41), but high (and significant) repeatability for most spatial parameters, i.e. autumn route (R = 0.64) and stopover sites (R = 0.59–0.87) in Europe, and wintering sites (R = 0.77–0.99) in sub‐Saharan Africa. This pattern of high spatial but low temporal within‐individual repeatability of migration between years contrasts other tracking studies of migrating birds that generally have found consistency in timing but flexibility in routes. High spatial consistency of migration in the great reed warbler may be due to it being a specialist in wetlands, an unevenly distributed habitat, favouring a strategy of recurrence at previously visited sites. Low temporal repeatability may be caused by large between‐year variation in carry‐over effects from the breeding season, high flexibility in decision rules during migration or high sensitivity to environmental factors (weather, wind) during migration.     

Climatic conditions during outward migration affect apparent survival of an arctic top predator,the peregrine falcon Falco peregrinus

In long‐lived species, population growth rate is highly sensitive to changes in adult survival. Despite the growing concerns regarding recent climate changes, few studies have investigated the effect of climatic conditions on survival in long‐lived wildlife that are either resident or breed in the Arctic. In this study, we evaluated the effect of climate across the annual life cycle (breeding, outward migration, wintering, and inward migration) on apparent annual survival of arctic‐breeding peregrine falcons. From 1982 to 2008, peregrine falcons breeding near Rankin Inlet, Nunavut, Canada were monitored, in part, to assess apparent annual survival (the product of true survival and site fidelity) using re‐observations of marked individuals. Our study indicated that apparent annual survival of adult peregrine falcons was correlated with indices of climatic conditions during outward migration (i.e., flight from the Arctic breeding grounds). These climatic indices (fall NAO of the current year and fall NAO with a lag of one year) explained 35% of the temporal variation in apparent annual survival of peregrine falcons. Our results suggest that this top‐predator is vulnerable to weather‐related environmental conditions encountered during fall migration.     

Simple signals indicate which period of the annual cycle drives declines in seasonal populations

For declining wild populations, a critical aspect of effective conservation is understanding when and where the causes of decline occur. The primary drivers of decline in migratory and seasonal populations can often be attributed to a specific period of the year. However, generic, broadly applicable indicators of these season‐specific drivers of population decline remain elusive. We used a multi‐generation experiment to investigate whether habitat loss in either the breeding or non‐breeding period generated distinct signatures of population decline. When breeding habitat was reduced, population size remained relatively stable for several generations, before declining precipitously. When non‐breeding habitat was reduced, between‐season variation in population counts increased relative to control populations, and non‐breeding population size declined steadily. Changes in seasonal vital rates and other indicators were predicted by the season in which habitat loss treatment occurred. Per capita reproductive output increased when non‐breeding habitat was reduced and decreased with breeding habitat reduction, whereas per capita non‐breeding survival showed the opposite trends. Our results reveal how simple signals inherent in counts and demographics of declining populations can indicate which period of the annual cycle is driving declines.     

Carry‐over effects of winter habitat quality on en route timing and condition of a migratory passerine during spring migration

We examined how conditions prior to migration influenced migration performance of two breeding populations of black‐and‐white warblers Mniotilta varia by linking information on the migrant's winter habitat quality, measured via stable carbon isotopes, with information on their breeding destination, measured via stable hydrogen isotopes. The quality of winter habitat strongly influenced the timing of migration when we accounted for differential timing of migration between breeding populations. Among birds migrating to the same breeding destination, males and females arriving early to the stopover site originated from more mesic habitat than later arriving birds, suggesting that the benefits of occupying high‐quality mesic habitat during the winter positively influence the timing of migration. However, male warblers arriving early to the stopover site were not in better migratory condition than later arriving conspecifics that originated from poor‐quality xeric winter habitat, regardless of breeding destination. The two breeding populations stopover at the study site during different time periods, suggesting that the lower migratory condition of early birds is not a function of the time of season, but potentially a migrant's migration strategy. Strong selection pressures to arrive early on the breeding grounds to secure high‐quality breeding territories may drive males from high‐quality winter habitat to minimize time at the expense of energy. This migration strategy would result in a smaller margin of safety to buffer the effects of adverse weather or scarcity of food, increasing the risk of mortality. The migratory condition of females was the same regardless of the timing of migration or breeding destination, suggesting that females adopt a strategy that conserves energy during migration. This study fills an important gap in our understanding of the linkages between winter habitat quality and factors that influence the performance of migration, the phase of the annual cycle thought to be limiting most migratory bird populations.     

Tracking climate impacts on the migratory monarch butterfly

Understanding the impacts of climate on migratory species is complicated by the fact that these species travel through several climates that may be changing in diverse ways throughout their complete migratory cycle. Most studies are not designed to tease out the direct and indirect effects of climate at various stages along the migration route. We assess the impacts of spring and summer climate conditions on breeding monarch butterflies, a species that completes its annual migration cycle over several generations. No single, broad‐scale climate metric can explain summer breeding phenology or the substantial year‐to‐year fluctuations observed in population abundances. As such, we built a Poisson regression model to help explain annual arrival times and abundances in the Midwestern United States. We incorporated the climate conditions experienced both during a spring migration/breeding phase in Texas as well as during subsequent arrival and breeding during the main recruitment period in Ohio. Using data from a state‐wide butterfly monitoring network in Ohio, our results suggest that climate acts in conflicting ways during the spring and summer seasons. High spring precipitation in Texas is associated with the largest annual population growth in Ohio and the earliest arrival to the summer breeding ground, as are intermediate spring temperatures in Texas. On the other hand, the timing of monarch arrivals to the summer breeding grounds is not affected by climate conditions within Ohio. Once in Ohio for summer breeding, precipitation has minimal impacts on overall abundances, whereas warmer summer temperatures are generally associated with the highest expected abundances, yet this effect is mitigated by the average seasonal temperature of each location in that the warmest sites receive no benefit of above average summer temperatures. Our results highlight the complex relationship between climate and performance for a migrating species and suggest that attempts to understand how monarchs will be affected by future climate conditions will be challenging.     

Impact of temperature on the breeding performance and selection patterns in lesser kestrels Falco naumanni

Adjusting breeding phenology to climate fluctuations can be problematic for migratory birds as they have to account for local environmental conditions on the breeding grounds while migrating from remote wintering areas. Predicting general responses to climate change is not straightforward, because these responses vary between migrant species due to the species‐specific ecological drivers of breeding behaviour. Therefore more information is needed on species with different ecological requirements, including data on heritability of migration, factors driving phenological changes and how climate affects selection pressures. Here, we measure heritability in settlement dates and the effect of local climate at the breeding grounds on settlement dates, reproductive success and selection patterns in a French population of a trans‐Saharan migratory insectivorous raptor, the lesser kestrel Falco naumanni, monitored and ringed since 1996. Heritability of settlement dates was low (0.07 ± 0.03), indicating a weak evolutionary potential. Nevertheless, plasticity in settlement dates in response to temperatures allowed earlier settlement when early spring was warmer than average. Reproductive success and selection patterns were strongly affected by temperature during settlement and chick rearing respectively. Warmer spring decreased selection for earlier settling and warmer early summer increased reproductive success. Interestingly, selection for earlier settling was more intense in cooler springs, contrasting with patterns from passerines lagging behind food peaks. Altogether, these results suggest a positive effect of warmer temperatures on breeding performances of lesser kestrels most likely because the French population is at the coolest boundary of the species European breeding range.     

Climate and density influence annual survival and movement in a migratory songbird

Assessing the drivers of survival across the annual cycle is important for understanding when and how population limitation occurs in migratory animals. Density‐dependent population regulation can occur during breeding and nonbreeding periods, and large‐scale climate cycles can also affect survival throughout the annual cycle via their effects on local weather and vegetation productivity. Most studies of survival use mark–recapture techniques to estimate apparent survival, but true survival rates remain obscured due to unknown rates of permanent emigration. This is especially problematic when assessing annual survival of migratory birds, whose movement between breeding attempts, or breeding dispersal, can be substantial. We used a multistate approach to examine drivers of annual survival and one component of breeding dispersal (habitat‐specific movements) in a population of American redstarts (Setophaga ruticilla) over 11 years in two adjacent habitat types. Annual survival displayed a curvilinear relation to the Southern Oscillation Index, with lower survival during La Niña and El Niño conditions. Although redstart density had no impact on survival, habitat‐specific density influenced local movements between habitat types, with redstarts being less likely to disperse from their previous year's breeding habitat as density within that habitat increased. This finding was strongest in males and may be explained by conspecific attraction influencing settlement decisions. Survival was lowest in young males, but movement was highest in this group, indicating that apparent survival rates were likely biased low due to permanent emigration. Our findings demonstrate the utility of examining breeding dispersal in mark–recapture studies and complement recent work using spatially explicit models of dispersal probability to obtain greater accuracy in survival estimates.     

Experimental old nest material predicts hoopoe Upupa epops eggshell and uropygial gland microbiota

Nest re‐use in birds has the potential cost of infection by parasites and pathogens but may also be a source of beneficial symbiotic bacteria transmitted horizontally. Eurasian hoopoes Upupa epops host antibiotic‐producing bacteria in their uropygial gland but only while breeding, which suggests that the nest‐hole may be a source of those symbionts. Interestingly, hoopoes do not build nests, thus might prefer for reproduction nest holes with soft materials from previous reproductions. Here, we tested experimentally this preference by installing in the field new nest boxes that were left empty or filled with either sawdust or a mixture of sawdust and hoopoe's nest material from the previous year. We explored the experimental effect on the composition of the uropygial secretion bacterial community, on eggshell bacterial loads, and on several proxies of reproductive success. Hoopoes bred significantly more often in nest boxes with nest material than in empty ones, but the type of nest material did not affect nest box occupancy. Eggs in nest boxes with old‐soft material harbored higher bacterial density on their shells, and the microbiota of the uropygial secretion of nestlings and females in these nest boxes differed from those in nest boxes without old‐soft material. Moreover, although the experiment did not affect breeding success or related proxies, several operational taxonomic units from female uropygial secretions were positively associated with hatching success. This is the first experimental evidence showing that re‐used nest material affects the bacterial community of the uropygial secretions of hoopoe females. This suggests that the nest material can be a source of strains for their incorporation to both the uropygial gland and eggshell communities, highlighting a possible advantage of nest re‐use previously unconsidered.