Eastern Whip-poor-will (<em>Antrostomus vociferus</em>) populations have declined considerably since 1970, primarily because of declines in insect prey and early successional forest breeding habitat. Previous studies on Whip-poor-wills have focused on tracking movements of adults on the breeding grounds and adults on the wintering grounds, tracking migratory pathways, and quantifying occupancy, yet few studies have focused on home range scale space use and habitat selection. We tracked 10 adult Whip-poor-wills from May–August 2022 at two Rhode Island, USA state management areas, Big River and Great Swamp, and five adult Whip-poor-wills (four of which were also tracked in 2022) from May–August 2023 at Great Swamp. We used diurnal locations to estimate home ranges for each individual and the extent of home range overlap for neighboring males, paired males and females, and the same males tracked in both years, as well as habitat selection at the home-range scale. Home range sizes of males and females were not different and averaged 18.05 ha. Home ranges of neighboring males minimally overlapped whereas paired males and females had a high degree of home range overlap. The four males that were tracked at Great Swamp in both years used very similar home ranges across years, suggesting that at least some individuals show site and home range fidelity. We found no support for selection for distance to any land cover types at the population level; however, 10 of 11 individuals selected for at least one land cover type and eight of 11 individuals selected for early successional forest openings (e.g., scrub and grassland), although the pattern of selection varied between individuals. These findings, when considered along with other published works on Whip-poor-will habitat selection and occupancy, underscore the importance of active forest management to maintain habitat mosaics on known Whip-poor-will breeding grounds.

Abstract Antrostomus vociferus (Eastern Whip-poor-will) have experienced a greater population decrease range wide than any other caprimulgid in North America. Hypotheses for this population reduction include conversion of open pasture to forest, increasing levels of urbanization, and the reduction of naturally occurring forest fires. Antrostomus vociferus forage over low forest canopies within early successional areas such as farmland intermixed with woody vegetation, forest patches recently cleared by fires and timber harvesting, and large artificial canopy breaks created by roads and power-line cuts. On institutional timber-harvest land in south-central West Virginia, we examined what site-specific and landscape features were positively associated with A. vociferus detection and occupancy probability. In June 2021 and 2022, we used autonomous recording units (ARUs) to estimate occupancy on a ∼104,000 ha working forest. To estimate occupancy, we targeted surveys in regenerating clear-cut forest stands with ages ranging from recently harvested (2021) to ∼20 yr since harvest. Antrostomus vociferus detection probability was positively related to lunar illumination, increasing by 10% for every 20% increase in illumination. Occupancy at sites above 900 m above sea level elevation was below 40% and decreased with distance from riparian zones. Antrostomus vociferus occupancy decreased as tree diameter increased and occupancy was positively related to the amount of grass ground cover. Thus, in a timber-harvested landscape with forest heterogeneity, A. vociferus were negatively associated with increasing elevation but occurred near riparian areas with open grassy areas and smaller trees. Implications of this study suggest that the management of mosaic forests at certain elevational thresholds (approximately ≤800 m) will increase the probability of A. vociferus occupancy.

ABSTRACTAimTo evaluate (1) whether three migratory nightjar species (Family Caprimulgidae) adhere to Bergmann's rule, (2) whether environmental factors on the breeding or wintering grounds determine body size, and (3) which mechanistic hypotheses best explain Bergmannian patterns in body size.LocationNorth and South America; Europe and Africa.TaxonEastern whip‐poor‐will (Antrostomus vociferus), Common nighthawk (Chordeiles minor) and European nightjar (Caprimulgus europaeus).MethodsWe used GPS tracking and morphometric data to assess competing hypotheses explaining variation in body size for each species, based on their breeding (n = 3388) and wintering (n = 189) locations.ResultsAll three species exhibited Bergmannian patterns in body size, providing the first evidence that nightjars conform to Bergmann's rule despite adaptations to severe environmental conditions. Environmental and geographic variables at breeding sites were stronger predictors of body size than wintering‐site variables. Although we found partial support for Bergmann's temperature regulation hypothesis, geographic variables, rather than specific environmental factors, emerged as the strongest predictors of body size variation.Main ConclusionsLatitude and longitude correlated strongly with environmental variables and migratory distance; thus, these geographical variables likely encompass many factors that influence body size in nightjars. The present study is among the first to use tracking data from individual birds to understand how environmental pressures across the annual cycle are related to body size. Our findings highlight the critical role of geographic breeding‐ground factors in shaping Bergmannian patterns, offering robust evidence to support nearly two centuries of research since Bergmann's rule was first described in 1847.

A large-scale assessment of eastern whip-poor-will (Antrostomus vociferus) occupancy across a gradient of forest management intensity using autonomous recording units

Automated radio telemetry systems have become a popular and invaluable tool in tracking the activity and movement of wild animals. However, many environmental conditions can hinder accuracy when tracking with this technology. For instance, study sites may contain multiple habitat types, each habitat uniquely affecting the signal strength received from tagged species. To investigate the influence of a structurally diverse study site on an automated radio telemetry system, we conducted this project at a restored and managed pine barren habitat that consisted of a mix of mature pitch pine, treated pitch pine, scrub oak, and hardwood forests. This site, Montague Plains Wildlife Management Area, Montague, Massachusetts, is also a known breeding ground for Eastern whip-poor-will (Antrostomus vociferus). To measure the relationship of radio signal strength with distance across each habitat, we used radio telemetry equipment manufactured by Cellular Tracking Technologies. We produced negative exponential decay functions measuring radio signal strength over distance and tested for differences among habitat types on radio signal strength (RSS). We found that decay function parameters significantly differed by habitat type, prompting us to investigate if accounting for these differences improved location estimate accuracy. To test this, we estimated known locations using trilateration methods with and without habitat calibration. Comparing these tests indicates that habitat-specific adjustments significantly improved location accuracy. Lastly, we visualized estimated RSS-based locations of 1 week of whip-poor-will data and compared them to GPS data generated from the same individual. Previous studies have accounted for types of environmental interference (like elevation) in the field but have avoided incorporating habitat-specific factors by working with node networks covering a relatively small area, but in this study, we examined the potential to scale up for larger areas and in more complex habitats.

Timing programs in animal migrants have been selected to synchronize movements that coincide with predictable resources on the breeding and nonbreeding grounds. Migrants face potential temporal conflicts if their migration schedules benefit from synchrony to conflicting rhythms associated with annual biogeographical (circannual) cues, lunar (circalunar) cues, or individually repeatable internal clocks. We repeat-tracked individuals of an avian lunaphilic species, Eastern Whip-poor-will (Antrostomus vociferus), for two to three successive autumn migrations to determine the influence of the lunar cycle, breeding location, and individual repeatability on migration timing. Almost all birds avoided departing for migration during a full moon, likely to take advantage of the bright moonlight to facilitate visual foraging and enhance pre-migration fattening. However, groups from two latitudinally distant sampling areas adjusted their autumn departure timing differently relative to the timing of the September full moon, presumably due to differences in seasonal prey availability. Individual repeatability increased throughout autumn migration, suggesting that the factors responsible for shaping migration timing may differ for different migration stages. Our results, that lunar synchrony, local climate, and individual internal clocks appeared to account for much of the variation in migration timing in whip-poor-wills, underscore the value of measuring potentially interacting factors that shape migratory behavior at species, group, and individual levels. It remains unclear if, or how, maintaining individually repeatable annual migration schedules provides an adaptive benefit for whip-poor-wills or other lunaphilic migrants. Further clarifying the reasons for phenotypic variation in whip-poor-will migration timing will improve predictions of their abilities to adjust migratory movements under changing environmental conditions.

Abstract Population trend estimates form the core of avian conservation assessments in North America and indicate important changes in the state of the natural world. The models used to estimate these trends would be more efficient and informative for conservation if they explicitly considered the spatial locations of the monitoring data. We created spatially explicit versions of some standard status and trend models applied to long-term monitoring data for birds across North America. We compared the spatial models to simpler non-spatial versions of the same models, fitting them to simulated data and real data from 3 broad-scale monitoring programs: the North American Breeding Bird Survey (BBS), the Christmas Bird Count, and a collection of programs we refer to as Migrating Shorebird Surveys. All the models generally reproduced the simulated trends and population trajectories when there were many data, and the spatial models performed better when there were fewer data and in locations where the local trends differed from the range-wide means. When fit to real data, the spatial models revealed interesting spatial patterns in trend, such as recent population increases along the Appalachian Mountains for the Eastern Whip-poor-will (Antrostomus vociferus), that were much less apparent in results from the non-spatial versions. The spatial models also had higher out-of-sample predictive accuracy than the non-spatial models for a selection of species using BBS data. The spatially explicit sharing of information allows fitting the models with much smaller strata, allowing for finer-grained patterns in trends. Spatially informed trends will facilitate more locally relevant conservation, highlight areas of conservation successes and challenges, and help generate and test hypotheses about the spatially dependent drivers of population change.

Although miniaturized data loggers allow new insights into avian migration, incomplete knowledge of basic patterns persists, especially for nightjars. Using GPS data loggers, this study examined migration ecology of the eastern whip‐poor‐will Antrostomus vociferus, across three migration strategies: flyover, short‐stay, and long‐stay. We documented migration movements, conducted hotspot analyses, quantified land cover within 1 and 5 km buffers at used and available locations, and modeled habitat selection during migration. From 2018–2020 we captured breeding whip‐poor‐wills from three study sites in Massachusetts and programmed GPS tags to collect data during fall and spring migration periods. Across 19 individual males (nine of them with repeated years of data), GPS tags collected 479 locations, where 30% were classified as flyover points, 33% as short‐stays, and 37% as long‐stay locations. We documented seasonal flexibility in migration duration, routes, and stopover locations among individuals and between years. Analyses identified hotspot clusters in fall and spring migration in the Sierra de Tamaulipas in Mexico. Land cover at used locations differed across location types at the 5 km scale, where closed forest cover increased and crop cover decreased for flyover, short‐stay, and long‐stay locations, and urban cover was lowest at long‐stay locations. Discrete choice modeling indicated that habitat selection by migrating whip‐poor‐wills differs depending on the scale and migration strategy. For example, at the 5 km scale birds avoided urban cover at long‐stay locations and selected closed forest cover at short‐stay locations. We suggest that whip‐poor‐wills may use land cover cues at large spatial scales, like 5 km, to influence rush or stay tactics during migration.

Abstract Migratory bird populations can be limited by events in disparate parts of the world. Birds wintering in tropical regions are facing rapid habitat loss, climate change, and intensive agricultural regimes, potentially contributing to population declines. However, an understanding of basic nonbreeding ecology of species, such as habitat and space use, is critical for determining if this is the case. Populations of the nocturnal/crepuscular Eastern Whip-poor-will (Antrostomus vociferus) have declined by 70% since the 1960’s, yet data on the species are sparse outside of the breeding season. We extracted data from 41 archival GPS tags deployed on whip-poor-wills and estimated nonbreeding home ranges and land covers used. We used satellite imagery and stable carbon and nitrogen isotope values from claws grown during the nonbreeding season to analyze how land cover and habitat moisture impacted home range size and relative trophic level. Forest was by far the most prevalent land cover used by whip-poor-wills, occurring in all home ranges and accounting for &amp;gt;80% of diurnal roosting points. We found that less forest, the presence of agriculture, and more edge (irrespective of land cover) were associated with larger home ranges. Stable isotope values differed by broadscale ecoregion but not local land cover characteristics in our study, indicating that regional idiosyncrasies or broadscale processes can be more important in determining stable isotope ratios. Our findings suggest that the loss, fragmentation, and replacement of forest by agriculture in the core of the whip-poor-will’s nonbreeding range may represent a threat to the species, as they rely heavily upon forest, and appear to alter space use in response to changes in forest cover.

Abstract Populations of avian aerial insectivores have declined across North America. A leading factor hypothesized to be driving these trends is a decline in prey populations, although a loss of suitable habitat on the landscape or other factors may also play a role. The Eastern Whip-poor-will (Antrostomus vociferus; hereafter: whip-poor-will) is an aerial insectivorous nightjar that has disappeared from many of its historic breeding locations. We investigated the role that food availability and land cover at multiple scales play in whip-poor-will distribution by estimating their abundance at 23 sites across central Illinois. To do this, we conducted nocturnal point counts to estimate whip-poor-will abundance and collected nocturnal insects using UV-light traps at these sites to quantify potential food abundance. Additionally, we described whip-poor-will diet using DNA metabarcoding of fecal samples. We found that the number of large moths at a site had a positive effect on the abundance of whip-poor-wills, aligning with our diet analysis which identified moths as the primary prey item for this species (present in 92% of samples). Whip-poor-wills also showed an affinity for forest edges, but only when edges were associated with high moth abundances. Conversely, developed land-cover in landscapes surrounding sites led to decreased whip-poor-will abundance. Given the continued expansion of developed areas, coupled with concerning trends in moth populations, declines in the abundance of this species may continue. Efforts should be made to protect and sustain moth populations and the impacts of development should be scrutinized in the pursuit of conserving whip-poor-wills.

Determining the year-round spatial distributions of at-risk avian migratory species is critical for effective conservation. High-precision tracking enables the identification of distant breeding and nonbreeding areas and their connectivity, as well as migratory routes and associated threats. We GPS-tracked two groups of Eastern Whip-poor-wills ( Antrostomus vociferus (A. Wilson, 1812)) that breed near the northern edge of their range, in Manitoba and northwestern Ontario (“west”), and in southern Ontario (“east”), Canada. The western-breeding birds were also ∼5° of latitude farther north than the eastern birds. We aimed to determine the degree of spatiotemporal overlap between the two groups during fall migration and at tropical wintering sites. We found that western-breeding birds departed earlier on migration than eastern-breeding birds, but we did not detect a difference in arrival timing to wintering sites. The two breeding groups retained spatial structure during migration, until all routes converged to circumnavigate the Gulf of Mexico. Western-breeding birds overwintered at sites farther south than eastern-breeding birds, consistent with a leapfrog pattern of migration. Quantifying the strength of migratory connectivity in at-risk species can be a first step toward defining breeding populations and informing customized conservation strategies throughout the annual cycle.

Flying animals use aerial habitats to forage, communicate and travel. However, human activities that fragment aerial habitat with built structures, noise, and chemical or light pollution, may limit the ability of wildlife to use airspace efficiently. Applying landscape connectivity theory to aerial habitats could reveal how long‐distance migrants respond to sources of aerial habitat fragmentation along their migratory routes. Artificial light at night is a major component of urbanization that fragments dark skies across North America. Attraction of nocturnal migrants to urban light is well documented, but species‐specific responses, especially throughout a full migration from breeding to wintering grounds, are not. We tested hypotheses about long‐distance migratory movements in relation to artificial light using a highly nocturnal, Nearctic‐Neotropical avian migrant (Eastern whip‐poor‐will Antrostomus vociferus ). We applied a resource selection framework at multiple spatial scales to explore whether GPS‐tracked birds (n = 10) responded to urbanization in general, or artificial light specifically, during migratory flights. We found little evidence of attraction to artificial light during nocturnal flights. Artificial light and urbanization were highly correlated and difficult to disentangle, but the birds generally avoided urban areas and selected dark‐connected skies for travel. Migratory stopovers (locations where GPS‐tracked birds (n = 20) paused for at least one night), were located almost exclusively in dark, rural areas. Our results illustrate that considering how nocturnal aerial migrants respond to both aerial and terrestrial habitat elements can improve our understanding of what may facilitate their long‐distance movements.

Abstract AimA full annual cycle approach to conservation and understanding of regional population trends requires an understanding of migratory connectivity. We present tracking data on the eastern whip‐poor‐will (Antrostomus vociferus), a Neotropical migrant that has declined by 70% in recent decades. When and where populations of this species are limited throughout the annual cycle is poorly understood.LocationBreeding area: midwestern United States; passage area and winter area: midwestern/southern United States, Mexico, Central America.MethodsWe utilized data from 52 archival GPS tags from five breeding areas covering a 9.5‐degree latitudinal span (~1000 km) of the whip‐poor‐will breeding range in the summers of 2017 and 2019. We identified migratory routes and spatiotemporal bottlenecks, stopover and wintering locations, calculated migratory connectivity throughout migration and on the wintering grounds and tested predictions for three latitudinal connectivity patterns.ResultsWhip‐poor‐wills circumvented the Gulf of Mexico, and populations across a large latitudinal gradient came together in eastern Texas in early October, resulting in decreased connectivity throughout migration. Breeding‐winter migratory connectivity was low (MC = 0.22 ± 0.12), with extensive overlap of core wintering areas in southern Mexico and Guatemala. The overlap of wintering areas by individuals from dispersed breeding latitudes suggests that whip‐poor‐wills most closely resemble telescopic migrants.Main conclusionsCircumventing the Gulf of Mexico influenced connectivity in the whip‐poor‐will, funnelling individuals into a small region in eastern Texas in migration and likely influencing breeding‐winter connectivity. Thus, geographically dispersed breeding populations overlap in space and time during migration and winter, and non‐breeding season conditions affecting populations (both positively and negatively) impact individuals from across the core breeding range. For example, extensive deforestation occurring in the whip‐poor‐will's core wintering area likely impacts individuals from all five deployment locations. We demonstrate that combining multiple indices of spatiotemporal cohesion is critical to fully understand how migratory animals are distributed in the non‐breeding season.

Abstract Chuck‐will's‐widow (Antrostomus carolinensis) and eastern whip‐poor‐will (Antrostomus vociferus) are nightjars in eastern North America that have declined 69% and 67%, respectively, in abundance since 1966, resulting in conservation concerns for these species. We investigated relationships between nightjar abundance and landscape composition, forest structure, and application of tree thinning and prescribed fire because of regional interest in woodland restoration and nightjar conservation. We conducted nocturnal nightjar surveys at 385 points in southern Missouri, USA, in 2014 and 2015 and related counts to pine (Pinusspp.) and hardwood basal area, canopy closure, percent forest cover, and percent of area thinned or burned within 500 m of survey points. We modeled abundance of chuck‐will's‐widow and eastern whip‐poor‐will using time‐removal models that included a detection process and an abundance process within a hierarchical Bayesian framework. We detected 534 eastern whip‐poor‐will and 186 chuck‐will's‐widow during surveys. Our data supported global models that included all 6 vegetation and management variables for both species. Chuck‐will's‐widow abundance was negatively related to hardwood basal area and peaked at intermediate values of percent area burned and percent forest cover. Eastern whip‐poor‐will abundance was negatively related to hardwood basal area and canopy cover, positively related to percent forest cover and percent of area burned, and peaked at low to moderate levels of percent of area thinned. Relationships to forest structure and management activities generally supported the conclusion that woodland restoration benefits nightjars and that chuck‐will's‐widow select landscapes with less forest cover than eastern whip‐poor‐will.

The Eastern Whip-poor-will (<em>Antrostomus vociferus</em>), an aerial insectivore experiencing population declines, was recently upgraded from Least Concern to Near Threatened status by the International Union for Conservation of Nature (IUCN), highlighting research needs to better understand threats to the species. Because little information is known concerning wintering ground ecology for the species, we used archival global positioning system (GPS) tags to examine wintering ground movement patterns and habitat selection for birds that breed throughout Massachusetts. Key findings document highly variable locations of overwintering home ranges (where birds overwinter from coastal South Carolina to mountains of El Salvador), 100% site fidelity to wintering grounds between years, and 20% of males occupying two home ranges in a season. Furthermore, birds avoided crop cover at the 5-km scale and preferred open and closed forest covers at the home range scale. Although some landscapes used by Whip-poor-wills had high crop cover, crop cover averaged 3.7 times greater in available plots than used plots at the 5-km spatial scale. Additionally, mean closed forest cover was 1.8x greater in the second home range for mobile birds than their first home range. The information gained from this study provides an improved understanding of the ecological needs for the Eastern Whip-poor-will on the wintering grounds and is critical for applying full life-cycle conservation strategies.

Multi-year monitoring of species distribution is important for conservation planners to understand population trajectories. In New York, USA, the Eastern Whip-poor-will (Antrostomus vociferus) is among several bird species that have been documented to be declining and has been monitored for several years through large-scale surveys such as the Breeding Bird Atlas and Breeding Bird Survey. We implemented a study to assess trends in site occupancy at 19 survey routes during 2014–2018 breeding seasons. We surveyed for Eastern Whip-poor-wills following the Center of Conservation Biology Nightjar Survey Network methodology and used these data to estimate yearly relative abundance, factors that may influence the probability of detection, probability of a site being occupied and potentially important landscape features, and dynamic processes of site colonization and extinction. The mean relative abundance ranged from 0.54 in 2016 to 0.89 in 2014, with all yearly estimates having 95% confidence intervals that overlapped. The probability of detection was negatively affected by the greatest wind speeds recorded (12.87–28.97 kph, [8–18 mph]). Site occupancy was relatively low each year ranging from 26% to 32% across all years. We observed a negative effect on site occupancy with survey sites located in the Adirondack ecozone of New York. We additionally found support for a negative effect of median elevation and a positive effect of area of hay and pasture on site occupancy within 675 m of survey sites. The probability of a site becoming colonized ranged from 0.05 to 0.14 and the probability of a site going extinct ranged from 0.14 to 0.42. Overall, we did not find support for a decreasing trend in site occupancy. The yearly relative abundance estimates and site occupancy estimates were small but did not decrease over time and the dynamic processes did not suggest increasing extinction or decreasing colonization rates. Occupied survey locations may represent some of the most suitable and stable habitat for these birds within the state. Important landscape characteristics of lower elevation and area of hay and pasture may be representative of forest mosaics that include open areas with forest edges at lower elevation, which has been documented in other studies.

ABSTRACTPopulations of the eastern whip‐poor‐will (Antrostomus vociferus; whip‐poor‐will) have declined throughout most of its range, making it a species of high conservation concern in nearly every state and province where it occurs. Researchers have reported whip‐poor‐wills are associated with forest stands with open canopies, and thus silviculture may be a promising means for promoting their populations, yet the ecological literature does not quantify fine‐scale habitat relationships capable of assisting with silviculture prescriptions. Our objective was to quantify the associations between whip‐poor‐wills, canopy openness, and other vegetation characteristics to provide managers with guidance for whip‐poor‐will management. Based on prior research, we hypothesized that whip‐poor‐wills may be associated with intermediate levels of canopy retention and that their numbers would also be affected by understory characteristics. We surveyed whip‐poor‐wills with point counts in managed forest at the Fort Drum Army installation in New York, USA, during 2015 and 2016 and collected vegetation measurements at each point count location to relate whip‐poor‐will occupancy with vegetation structure and composition. Whip‐poor‐will occupancy was strongly related to intermediate levels of basal area, with peak occupancy at 13.8 m2/ha, a value that corresponds to forest denser than most shrublands but more open than closed‐canopy forest. Whip‐poor‐will presence was negatively related to understory height, which is consistent with prior studies. These findings provide managers with quantitative targets that can be used to increase or maintain whip‐poor‐will numbers and abundance of other disturbance‐associated species similarly unable to persist in unmanaged forests stands. © 2021 The Wildlife Society.

Grahame, E. R. M., K. D. Martin, E. A. Gow, and D. R. Norris. 2021. Diurnal and nocturnal habitat preference of Eastern Whip-poor-wills (Antrostomus vociferous) in the northern portion of their breeding range. Avian Conservation and Ecology 16(2):14. https://doi.org/10.5751/ACE-01929-160214

Circadian migration patterns for most migratory birds can be partitioned into day and night flights, but can be flexible at barrier crossings. Whether obligate nocturnal species opportunely use some daylight during migration has not been previously investigated. We tested the night constraint hypothesis using autumn Global Positioning System (GPS) tracking of a migratory nightjar species (Eastern Whip-poor-will, Antrostomus vociferus), and found that a minimum of 89% of travel occurred in darkness. All seven GPS-tracked individuals avoided crossing the Gulf of Mexico, which would have required some daytime flight. Future research should investigate the mechanisms and implications of light restrictions on the migratory movements of nocturnal species.

Phenology match–mismatch usually refers to the extent of an organism's ability to match reproduction with peaks in food availability, but when mismatch occurs, it may indicate a response to another selective pressure. We assess the value of matching reproductive timing to multiple selective pressures for a migratory lunarphilic aerial insectivore bird, the whip‐poor‐will (Antrostomus vociferus). We hypothesize that a whip‐poor‐will's response to shifts in local phenology may be constrained by long annual migrations and a foraging mode that is dependent on both benign weather and the availability of moonlight. To test this, we monitored daily nest survival and overall reproductive success relative to food availability and moon phase in the northern part of whip‐poor‐will's breeding range. We found that moth abundance, and potentially temperature and moonlight, may all have a positive influence on daily chick survival rates and that the lowest chick survival rates for the period between hatching and fledging occurred when hatch was mismatched with both moths and moonlight. However, rather than breeding too late for peak moth abundance, the average first brood hatch date actually preceded the peak moth abundance and occurred during a period with slightly higher available moonlight than the period of peak food abundance. As a result, a low individual survival rate was partially compensated for by initiating more nesting attempts. This suggests that nightjars were able to adjust their breeding phenology in such a way that the costs of mismatch with food supply were at least partially balanced by a longer breeding season.