Post-fledging Movements Research Articles

Survival, Nest Site Affiliation and Post-Fledging Movements of Danish White-Tailed Eagles (Haliaeetus albicilla)

The early life movement patterns of long-lived, large raptors, such as the white-tailed eagle (Haliaeetus albicilla), remain largely unexplored. In this study, we have tracked 22 individuals of white-tailed eagles hatched in Denmark to investigate key parameters, including survival rates, causes of death, nest site fidelity, geographical distribution, and dispersal behaviors. Our analyses are based on approximately 340,000 GPS/GSM telemetry positions from the 22 individuals. We found that survival rates were lower in the first year of life, especially among females, but increased in subsequent years. The primary causes of death were wind turbine collisions and avian influenza. Movement analyses revealed that juvenile eagles frequented nest sites in August and September, with females showing earlier exploratory flights and dispersal. Both males and females spent most of their first calendar year near their nest sites. In the second calendar year, a significant proportion of their time was spent at well-known white-tailed eagle resting areas in Denmark, as well as visiting neighboring countries. Notably, one individual set a new distance record for a Danish GPS-tagged white-tailed eagle, venturing at least 1750 km away from its nest site to visit Sweden, Finland, Russia, and Norway. Our results, indicating that juvenile white-tailed eagles continue to utilize nest sites into September, suggest an extension of the recommended time period for nest protection zones provided by BirdLife Denmark (DOF).

The spatiotemporal properties of artificial feeding schemes influence the post-fledging movement of Egyptian Vultures

Abstract Many vulture populations have severely declined in the past decades, showing high juvenile mortality. To support these populations, feeding stations are used to increase food availability and to supply food without antibiotics and toxic compounds. Yet, supplying food at feeding stations may affect vulture behavior. We present a large-scale field experiment testing how different food provision schemes affected the movement of Egyptian Vultures (Neophron percnopterus). We used GPS transmitters harnessed to 18 vulture chicks and described their movements post-fledging. We categorized the vultures into 3 groups according to the feeding scheme used at feeding stations near their nests: frequent and spatially dispersed food supply (FD); non-frequent and spatially dispersed food supply (NFD); and frequent food supply, concentrated in one location (FC). We found that birds from all three groups increased their roosting distances from the nest with fledgling age, with the NFD and FC groups showing a greater increase than the FD group. Additionally, all 3 groups increased their daily flight distances, with the NFD group presenting the largest increase and the FD group presenting the smallest increase. Our findings offer new insights into the relevance of spatiotemporal differences in the management of feeding stations and show its effect on movement during birds’ early life stages, creating 2 main movement patterns: local and regional. Our findings can help decide upon the preferable feeding scheme in a way that will either encourage or reduce the early dispersal distances of fledglings, according to long- and short-term conservation objectives. For example, local movements during the post fledging period to known and stable food resources may reduce the risk of anthropogenic-induced mortality, while it may negatively affect long-term survival by hindering foraging, flight, and exploring skills and affect dispersion to future breeding sites.

Post-Fledging Movements and Factors that Influence Permanent Departure of Juvenile Crested Caracaras in Florida

ABSTRACT We tracked 48 young Crested Caracaras (Caracara plancus) in south-central Florida from fledging through their first year and sought to define the post-fledging pre-dispersal period and the timing and drivers of permanent departure (PD) from the natal area. By examining Euclidean distances between telemetry locations and the nest for each tagged caracara, we defined the post-fledging dependency period as the first 2 mo after fledging, when fledglings remained mostly within 2.5 km of the nest and were dependent on their parents for food. Before PD, young caracaras explored areas as much as 11 km from their nest but returned to the natal area, resulting in areas used by fledglings up to 6 times the average home range size of an adult breeding pair. Some caracaras remained within their parents’ home range for several months after fledging, even after becoming independent of their parents for food. A fledgling permanently departed its natal area when telemetry indicated it made an abrupt long-distance movement away from its natal area and did not return. We used generalized linear mixed models and a hierarchical modeling approach to test environmental and biological factors that may affect the timing of PD. The most supported model indicated that PD depended on parental reproductive strategy and on the timing of fledging relative to the length of the breeding season. Birds with parents that raised only one brood remained in the natal area for 11.6–21.0 wk longer than birds with parents that raised multiple broods in the same breeding season; fledglings from the first of two broods departed at a younger age, suggesting that the PD decision is partially triggered by the level of parental investment in the first and subsequent brood. Additionally, birds that fledged early in the breeding season departed the natal area 2.8–12.2 wk earlier than those that fledged later in the breeding season, and birds that were exposed to high heat during the nestling stage departed the natal area earlier than those exposed to less heat. The period between fledging and permanent departure from the natal area is important for the conservation of species with delayed dispersal. When developing a conservation strategy for Florida’s caracara population, attention should be paid to protecting areas used by fledglings until PD rather than just focusing on a limited protection zone around the nest.

Post-fledging movements of Atlantic Puffins from Skomer Island

The movements of seabirds during the immature period generally remain poorly understood, primarily due to the challenges involved with tracking birds that do not regularly return to a nest. This knowledge gap prevents us from gaining a full understanding of the areas used by seabird populations. Here, we attempted to track the post-fledging movements of Atlantic Puffins Fratercula arctica from Skomer Island (Wales, UK), by deploying geolocators on chicks ready to leave the nest. Despite our very small return rate (just two loggers out of 54, recording 485 and 196 days of data after fledging, respectively), our results provide a first glimpse into the distribution and scale of movements of young Puffins after fledging. The young Puffins undertook movements comparable in scale to those of post-breeding adults, and there were considerable differences between the two individuals. New initiatives to track juvenile seabirds in much larger numbers will hopefully soon provide more insight into seabird post-fledging movements.

Natal Dispersal and Seasonal Migration of White-Tailed Sea Eagles in Khabarovsk Krai (Russia) and Hokkaido (Japan)

White-Tailed Sea Eagles (Haliaeetus albicilla) become sexually mature at 5–6 years and the conditions of habitats and flight paths for local and seasonal movements in the nomadic period between post-fledging and breeding territory occupation are important in terms of population demographic relevance. The purpose of this study is to elucidate post-fledging movements, seasonal migrations, and habitats of immature White-Tailed Sea Eagles by GPS tracking. GPS transmitters were attached to nestlings of White-Tailed Sea Eagles at the middle basin of Amur River (around Slavyanka; 49°50'N, 136°76'E) and Lake Chukchagir (51°59'N, 136°36'E) in Khabarovsk Krai, Russia, and at Abashiri (44°1'N, 144°16'E) in eastern Hokkaido, Japan, in the breeding seasons of 2017–2022. Habitats used by GPS-tagged immatures were investigated with satellite images and field observations. The dispersion of post-fledging sea eagles from their natal nests occurred in autumn (September–October) for both sites in Khabarovsk and Abashiri. The first destinations in dispersal movements were river tributaries or lakes in floodplains in Khabarovsk (n=4) and rivers in Abashiri (n=2). Start timing and the first destination of emigration from natal sites for both breeding areas was considered to be related with upstreaming of salmonid fish for spawning. All of three juveniles fledged in Khabarovsk and tracked at least until their first winter wintered at the coastal area of Primorsky Krai, Russia, approximately 800–1,000 km south of their birthplaces, however, one juvenile took a different migration route to the wintering ground than the other two. Besides, two eagles tracked for more than two years after their birth in Khabarovsk showed the same migration routes in spring and autumn, and in the first year and subsequent years, respectively. Meanwhile, juvenile eagles fledged in Abashiri (n=2) moved to the places up to about 150 km south of their natal sites in their first winter, despite the fact that some major wintering grounds for sea eagles exist around their birthplace. Previous study reported that some colour-ringed immature White-Tailed Sea Eagles fledged at nests in Nemuro (43°19'N, 145°35'E), located approximately 100 km southeast direction of Abashiri, had been observed around their birthplaces in winter (Shiraki, 2002). Not only food availability but also genetic factor may be involved in determination of the wintering area. White-Tailed Sea Eagles over one year old from the nests in Khabarovsk (n=2) and in Abashiri (n=1) visited the vicinity of their natal sites during spring and summer. As White-Tailed Sea Eagles are known to have a tendency to nest in the natal area, young eagles might assess breeding opportunities around their natal sites. Immature White-Tailed Sea Eagles with GPS mostly stayed at habitats with food supplied from human activities, such as small fish discarded in fishery, marine waste, Sika Deer (Cervus nippon) residue left behind after hunting or killed in collisions with vehicles or trains, during winter in both of Primorsky and Hokkaido.

Exogenous corticosterone and melanin-based coloration explain variation in juvenile dispersal behaviour in the barn owl (Tyto alba).

Natal dispersal affects many processes such as population dynamics. So far, most studies have examined the intrinsic and extrinsic factors that determine the distance between the place of birth and of first breeding. In contrast, few researchers followed the first steps of dispersal soon after fledging. To study this gap, we radio-tracked 95 barn owl nestlings (Tyto alba) to locate their diurnal roost sites from the fledging stage until December. This was used to test whether the age of nest departure, post-fledging movements and dispersal distance were related to melanin-based coloration, which is correlated to fitness-related traits, as well as to corticosterone, a hormone that mediates a number of life history trade-offs and the physiological and behavioural responses to stressful situations. We found that the artificial administration of corticosterone delayed the age when juveniles left their parental home-range in females but not in males. During the first few months after fledging, longer dispersal distances were reached by females compared to males, by individuals marked with larger black feather spots compared to individuals with smaller spots, by larger individuals and by those experimentally treated with corticosterone. We conclude that the onset and magnitude of dispersal is sensitive to the stress hormone corticosterone, melanin-based coloration and body size.

Post-fledging movements, mortality and migration of juvenile northern gannets

Studying the at-sea movements and behaviour of juvenile seabirds is logistically challenging, but new technologies now allow tracking birds on their first migration, giving a more complete picture of population-level spatial ecology. We investigated the post-fledging migration of juvenile northern gannets Morus bassanus from the world’s largest colony, at Bass Rock, Scotland. We first examined the movements and survival of 38 juveniles over their initial days at sea with GPS precision for up to 53 d post-fledging. We then compared their migration journeys with those of 35 adults tracked with geolocators. Almost one-third of juveniles died within 2 mo of leaving the colony, and this mortality was often associated with apparent uncertainties in their direction of migration, including marked, abrupt and often repeated changes in bearing within the North Sea. Both juveniles and adults then migrated as far as the Canary Current Large Marine Ecosystem (CCLME) off the Atlantic coast of West Africa, initially taking both clockwise and counter-clockwise routes around the UK. Juveniles covered a distance each day similar to that of adults, but they reached the CCLME much more quickly, mainly because they travelled more directly, staying close to the coast throughout most of their migration, whereas adults additionally spent long periods over relatively restricted areas of ocean further offshore. The CCLME is a hotspot of unregulated fishing activity, and our findings highlight the importance of this region across different age-classes of birds, echoing previous calls that the regional strengthening of marine conservation should be a high priority.

Independence day: Post-fledging movements and behavior of adult Eastern Towhees (Pipilo erythrophthalmus) in landscapes managed for American Woodcock (Scolopax minor)

ABSTRACT Umbrella species management offers a potential solution to the financial and logistical challenges of managing for the many declining species in early-successional forests, a habitat that ...

Facultative polygamy may influence post-fledging movements in a brood-splitting passerine

Animal space-use patterns can vary widely with age, sex, and stage of the annual cycle, but the factors that drive pattern shifts are poorly understood. Here, we provide preliminary evidence that mating strategy (i.e., polygamy) influences movements of parents attending recently fledged young. We monitored the space use during the post-fledging period for Vermivora spp. broods led by a male and female with a split brood in 2014 and the same male with 2 fledglings in 2015. We observed contextand sex-specific space-use patterns that seemed to be driven by the male's attention to a secondary polygamous nest in 2014. When attending his secondary nest, the male restricted his primary brood's movements to within the nesting habitat close to his secondary nest until the nest failed. This pattern was distinct from movements of both the 2014 female and the same male in 2015 when he lacked a secondary nest. These observations may explain some reports from other studies that female-led broods disperse farther than male-led broods. Future work should explicitly consider the potential impacts of facultative polygamy on post-fledging space use, especially in species traditionally considered monogamous.

Inter-island Movements of Two Barbary Falcon (Falco peregrinus pelegrinoides) Juveniles in the Canary Islands

We studied the post-fledging movement of two sibling (male and female) juvenile Barbary Falcons (Falco peregrinus pelegrinoides) hatched in Lanzarote (Canary Islands) in 2011 using satellite tracking. Birds were tracked from fledging in May to the end of November, when the signals of both transmitters were lost. During the first 45 d following fledging, both birds behaved similarly and made some flights 3000 km from the nest, probably using a ship as a perch. Because Barbary Falcon populations of the Canary Islands are listed as “threatened” due to anthropogenic threats (e.g. collisions with human-made structures, illegal shooting, nest-robbing, and hybridization with escaped falconry falcons) and little is known about their post-fledging dispersal movements, more studies of such life-history characteristics, using ringing and remote sensing, are urgently needed to develop management actions for their conservation.

Post-fledging movement and spatial ecology of the endangered Cape Vulture (Gyps coprotheres)

The post-fledging dependence period (PFDP) is one of the most critical stages in the life history of some avian species. Birds are particularly sensitive to mortality during this stage as they must learn essential skills, such as efficient locomotion, proficient food location and predator avoidance. Knowledge of the PFDP would provide valuable information for conservation management of endangered species, many of which experience high juvenile fatality rates. Post-fledging movements of five endangered Cape Vultures were recorded using Global Positioning System/Global System for Mobile communication telemetry in South Africa. Home range sizes, distances travelled from the nest and habitat use were determined over 11 months during the PFDP. Fledglings increased their home range progressively for the first 2 months, then exhibited a rapid increase in home range size associated with dispersal from their natal colony. Maximum net daily distance also rapidly increased following the dispersal period. A preference for protected areas and woody vegetation (representing cliff faces used for roosting) in terms of habitat use for foraging was evident. The knowledge of the movement and habitat use of juvenile Cape Vultures can aid in the effective conservation planning for the species. Conservation programs in identified areas can be focused on power line and wind-farm mitigation, areas of supplementary feeding and anti-poisoning events.

Post-fledging movements and habitat associations of White-tailed Sea Eagles (Haliaeetus albicilla) in Central Asia

ABSTRACT Behavior of young birds can have important consequences for population dynamics. We investigated the autumnal post-fledging movements of 3 White-tailed Sea Eagles (Haliaeetus albicilla) hatched in Kazakhstan. All 3 eagles traveled south, flying on average 25–108 km/d. Movement was nonrandom, with eagles generally traveling near mosaics of forest, open areas, and water, and rarely using areas with little vegetation. As the first study of movements of White-tailed Sea Eagles in arid Central Asia, this study provides insight into potential limiting factors and how these birds interact with their environment during long-distance movements.

Insights into post-fledging dispersal of Bearded Vultures Gypaetus barbatus in southern Africa from GPS satellite telemetry

ABSTRACTCapsule: Fledglings progressively increase their home range size and ranging behaviour as they age.Aims: To examine the home range size and ranging behaviour of Bearded Vulture fledglings during the post-fledging dependence period and determine the onset of natal dispersal.Methods: Post-fledging movements of three individuals were investigated in southern Africa using global positioning system (GPS) satellite telemetry which enabled home range sizes and distances travelled from the nest to be calculated.Results: Fledglings increased their home range size from an average of 0.4–10 999 km2 (100% Minimum Convex Polygons) and 9.13–11 466 km2 (fixed 95% kernels) within the first six months post fledging. They also increased home range use as they aged with maximum daily distances travelled from the nest occurring between 98 and 136 days post fledging (when fledglings were aged between 222 and 262 days), after which time they dispersed from their natal area. Distances between fixes were highest during the dispersal period.Conclusion: GPS satellite telemetry allows us to accurately demonstrate how fledglings progressively increase and use their home ranges as they age and undertake pre-dispersive exploratory flights. Results confirm the notion that juveniles disperse at the onset of the following breeding season and suggest that dispersal occurs earlier in the southern hemisphere.

Behavioral development and habitat structure affect postfledging movements of songbirds

ABSTRACTPostfledging survival of neotropical migrant songbirds has been linked to seasonal and annual changes in the environment and to individual condition. Understanding what influences variation in postfledging movements may provide insight into the differential value of habitat across life‐history stages. We conducted a radio‐telemetry study of postfledging ovenbirds (Seiurus aurocapilla; n = 45) and Acadian flycatchers (Empidonax virescens; n = 62) in mature‐forest fragments from 2012 to 2015 in Missouri, USA. We documented variability in behavior and space use and used generalized linear mixed models to evaluate the relationship of postfledging movement rates to individuals’ condition, temporal variables, and local habitat variables. We found effects of age and season on movement distances for both study species. Additionally, daily movements of fledgling ovenbirds were negatively related to understory foliage density, a characteristic previously linked to increased survival. Habitat features are useful in predicting the postfledging movements of ovenbirds. By including behavioral development (age) and season in movement models, we were able to isolate and detect habitat effects on movement of ovenbirds and Acadian flycatchers. We suggest researchers use models of daily movement to further strengthen resource quality hypotheses generated by habitat selection and survival studies. © 2016 The Wildlife Society.

Post-fledging movements of white-tailed eagles: Conservation implications for wind-energy development.

The presence of poorly sited wind farms raises concerns for wildlife, including birds of prey. Therefore, there is a need to extend the knowledge of the potential human-wildlife conflicts associated with wind energy. Here, we report on the movements and habitat use of post-fledging satellite-tagged white-tailed eagles in Finland, where wind-energy development is expected to increase in the near future. In particular, we examine the probability of a fledgling approaching a hypothetical turbine that is placed at different distances from the nest. We found that this probability is high at short distances but considerably decreases with increasing distances to the nest. A utilisation-availability analysis showed that the coast was the preferred habitat. We argue that avoiding construction between active nests and the shoreline, as well as adopting the currently 2-km buffer zone for turbine deployment, can avoid or minimise potential impacts on post-fledging white-tailed eagles.

Adult and hatch-year blackpoll warblers exhibit radically different regional-scale movements during post-fledging dispersal.

Using a broad-scale automated telemetry array, we explored post-fledging movements of blackpoll warblers breeding in Atlantic Canada. We sought to determine the full spatial scale of post-fledging dispersal, to assess support for three hypotheses for regional-scale post-fledging movement, and to determine whether learning influenced movement during this period. We demonstrated that both young and adults moved over distances more than 200 km prior to initiating migration. Adults moved southwest, crossing the Gulf of Maine (GOM), consistent with the commencement of migration hypothesis. Hatch-year birds exhibited less directional movements constrained geographically by the GOM. Their movements were most consistent with exploration hypotheses--that young birds develop a regional-scale map to aid in habitat selection, natal dispersal and subsequent migrations.

Association of Sex, Fledging Date, and Sibling Relationships with Post-Fledging Movements of Burrowing Owls in a Nonmigratory Population in the Imperial Valley, California

Natal dispersal is an important driver of population and colonization dynamics, yet factors that affect timing and distance of post-fledging movements are poorly understood. We studied post-fledging movements of 34 (12 male and 22 female) juvenile Burrowing Owls (Athene cunicularia) between June 2002 and April 2003, in a nonmigratory population in the Imperial Valley, California. We found high variation in movement patterns among individuals. Juvenile Burrowing Owls left their nest throughout the year, with two females (6%) remaining within 100 m of their natal burrow until the beginning of the following year's breeding season. Juvenile Burrowing Owls moved up to 11.7 km (males: 397 ± 124 m; females 1762 ± 630 m) between emergence from the nest to the following breeding season. Those that fledged early in the season remained closer to their nests for a longer period than those that fledged later in the season. Female Burrowing Owls remained ≤100 m from their natal nests for a longer duration than males. Members of male–female, but not male–male, sibling pairs were more likely to be within 100 m of one another than members of female–female sibling pairs. After members of sibling pairs were >100 m apart, distance between members of sibling pairs was related only to time since fledging. Our study, conducted in a highly simplified agricultural environment, provides evidence that sex, fledging date, and sibling relationships can be responsible for the high individual variation in post-fledging movements of Burrowing Owls that has often been attributed to environmental variation.La dispersión natal es un impulsor importante de las dinámicas poblacionales y de colonización, sin embargo se conoce muy poco sobre los factores que afectan los tiempos y la distancia de los movimientos post abandono del nido. Estudiamos los movimientos posteriores al emplumamiento de 34 (12 machos y 22 hembras) individuos juveniles de Athene cunicularia entre junio del 2002 y abril del 2003, en una población no migratoria en el Valle Imperial, California. Encontramos una elevada variación en los patrones de movimiento entre individuos. Los juveniles de A. cunicularia dejaron sus nidos a lo largo del año, con dos hembras (6%) que permanecieron a menos de 100 m de su madriguera hasta el comienzo de la próxima época reproductiva. Los juveniles de A. cunicularia se movieron hasta 11.7 km (machos: 397 ± 124 m; hembras: 1762 ± 630 m) desde la emergencia del nido hasta la próxima estación reproductiva. Aquellos individuos que dejaron el nido a comienzos de la temporada permanecieron más cerca de sus nidos por un periodo más prologado que aquellos que abandonaron el nido más tarde en la temporada. Las hembras de A. cunicularia permanecieron ≤100 m de sus nidos natales durante más tiempo que los machos. Fue más probable encontrar a miembros de pares de hermanos macho–hembra, pero no macho–macho, a menos de 100 m el uno del otro que miembros de pares de hermanos hembra–hembra. Después de que los miembros de pares de hermanos estuvieron separados por >100 m la distancia entre los miembros de un par de hermanos estuvo relacionada sólo con el tiempo transcurrido desde la partida del nido. Nuestro estudio, realizado en un ambiente agrícola altamente simplificado, proporciona evidencia de que el sexo, la fecha del emplumamiento y las relaciones entre hermanos pueden ser responsables de la alta variación individual de los movimientos posteriores al emplumamiento de individuos de A. cunicularia, que a menudo ha sido atribuida a la variación ambiental.

Postharvest regeneration, sciurid abundance, and postfledging survival and movements in an Ovenbird population

ABSTRACT Several studies have emphasized the importance of postfledging survival when estimating avian population growth rates, yet high variation exists in reported estimates. Mechanisms influencing postfledging survival also remain poorly understood. The influences of local habitat quality and landscape context on postfledging movements also remain largely undocumented. We measured daily postfledging survival and movements in Ovenbirds (Seiurus aurocapilla) in selection cut plots (30–40% basal area removal) and controls. Specifically, we tested predictions from the “concealment” hypothesis (higher survival/shorter movements with increased fledgling concealment), “body condition” hypothesis (higher survival/longer movements with increased body mass), and “predator abundance” hypothesis (higher survival/shorter movements when predator abundance is low) by monitoring fledgling survival (n = 55) and movements (n = 41) during the first 2 weeks postfledging. Fledglings were monitored over 2 breeding seasons i...

Movements of imperial eagle Aquila heliaca juveniles and description of monitored areas in the border zone between Austria, Hungary and Slovakia

Abstract Five juveniles of the imperial eagle were tracked during 2011-201 2. Movements were monitored in the western part of Slovakia and in the border area between Austria, Hungary and Slovakia. Three eagles came from the Záhorská nížina Lowlands and the others from the Malé Karpaty Mts and the Podunajská nížina Lowlands. Post-fledging movements were recorded in areas around the nests. Post-fledging areas covered a large territory (minimum convex polygons - 89, 941 , 969 km2). During the postfledging period the eagles carried out exploratory flights (1 2-33 km from the nest). One temporary settlement area (TSA) was identified in the border area between Austria, Hungary and Slovakia (minimum convex polygon - 68 km2). Two eagles with radio transmitters were recorded in this area. In the TSA and the post-fledging areas two habitat categories were dominant: arable land and forests. Heterogeneous agricultural areas were also important in the TSA (8%).

Postfledging movements in birds: Do tit families track environmental phenology?

ABSTRACT. Recent research on reproduction in animals has emphasized phenology and prey matching in the long term and on large spatial scales (e.g., linked to global climate change). We studied how individuals within one reproductive cycle and at small spatial scales may try to maximize access to food resources that vary in space and time. Herbivorous mammals are known to track favorable phenological stages of their food plants and move seasonally on the landscape. Whether phenology similarly affects spatial movements of birds on their breeding grounds is largely unknown. We studied postfledging movements of Blue Tits (Cyanistes caeruleus) and Great Tits (Parus major) when the young were escorted by parents during 19 to 43 days posthatching. This was done over 4 years in a 1.6-km2 woodland area in Norway in which an elevational gradient (105–266 m) caused a phenological delay in vegetation and peak abundance of caterpillar prey at the higher elevations. Postfledging movements were similar in the two tit sp...