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1.
ABSTRACT Dispersal events can affect the distribution, abundance, population structure, and gene flow of animal populations, but little is known about long‐distance movements due to the difficulty of tracking individuals across space. We documented the natal and breeding dispersal of shrubland birds among 13 study sites in a 1000 km2 area in southeastern Ohio. In addition, we radio‐marked and tracked 37 adult males of one shrubland specialist, the Yellow‐breasted Chat (Icteria virens). We banded 1925 juveniles and 2112 adults of nine shrubland species from 2002 to 2005. Of these, 33 (1.7%) juveniles were encountered in subsequent years (2003–2006) as adults (natal dispersal) and 442 (20.9%) birds initially banded as breeding adults were re‐encountered in subsequent years (breeding dispersal). Apparent survival of juvenile shrubland birds on their natal patches was 0.024 (95% CI 0.016–0.036). After accounting for the probability of detection, we found that 21% of birds banded as juveniles and recaptured as adults returned to their natal patches, whereas 78% of adult birds showed fidelity to the patch where they were originally captured. Moreover, natal dispersers tended to move farther than breeding dispersers (corrected natal median = 1.7 km ± 0.37; corrected breeding median = 0.23 km ± 0.10). We used our estimates of natal dispersal and annual apparent survival to estimate true survival at 0.11 (95% CI 0.07–0.18) for juveniles in their first year. However, this estimate was only applicable for birds dispersing within 7 km of their natal patches. Interpatch movements of radio‐marked Yellow‐breasted Chats were not uncommon, with 13 of 37 males located in more than one habitat patch. Overall, we observed low natal philopatry, but high adult site fidelity for shrubland birds in our study area. Considering the frequency of short‐distance movements observed (median = 531 m, range = 88–1045 m), clustering of patches within 1 km might facilitate use of shrubland habitat.  相似文献   

2.
PHILIP WARREN  & DAVID BAINES 《Ibis》2007,149(4):758-762
Radio-transmitters were fitted on 146 juvenile Red Grouse Lagopus lagopus scoticus (116 hens, 30 cocks) to study the timing, frequency and distances of dispersal on managed grouse moors in northern England between 1999 and 2002. A third of the radiotagged birds were shot. Disturbance on shoot days meant that radiotagged birds were shot at points more than twice as far from the catch location as the points when they were last recorded alive. For birds that were shot, the distance from the catch location to the place they were shot was more than twice the natal dispersal distances of the survivors. Therefore, shot birds were excluded from the dispersal analysis. Juvenile hens dispersed significantly further (mean 861 m, range 50–4660 m) than juvenile cocks (mean 343 m, range 90–660 m). Dispersal distances were not related to predispersal Grouse densities at the catch area in summer or to Grouse densities in the following spring. The mean date of dispersal for juvenile hens was 6 October ± 4 days (se), with only one record of spring dispersal (14 March) of 1490 m.  相似文献   

3.
Thirteen juvenile Golden Eagles Aquila chrysaetos were tracked during their first year of life using satellite telemetry. Distances to the nest attained during that period and the age at the onset of juvenile dispersal were explored. The performance of nine different criteria to determine that age was analysed. In general, after a brief period of restricted movements around the nest, the average distance to the nest increased with time. Maximum distances to the nest ranged between 57.7 and 184.3 km, and were considerably greater in females (mean ± sd, 138.5 ± 44.5 km) than in males (70.5 ± 14.0 km). No sex difference was observed in the age at which that distance was attained (males: 329 ± 32 days, females: 312 ± 20 days). The onset of juvenile dispersal took place around the fifth month of life (September in Spain). Eight of the nine criteria provided similar results, suggesting that in Spain dispersal starts when birds are between 140 and 180 days old, and that the post-nestling period lasts between 60 and 120 days. For future studies, to determine the age at which the onset of juvenile dispersal occurs, we recommend the use of either the first day on which individuals were located beyond the mean distance between nests of different pairs (10 km in our study area), or the date of the record midway between the first and the last location recorded during the month in which the maximum variability in the distance to the nest was observed.  相似文献   

4.
Variation in timing and distance of dispersal movements of juvenile birds may result from differences in competitive ability. Dispersal by low-ranking juveniles may be initiated before dominants if the latter force subordinate siblings from natal areas. Conversely, when vacant territories are limited and are acquired on a first-come first-served basis, selection could operate on young to disperse as early as possible. In this case, dominant individuals with priority of access to resources in the natal area will mature more quickly and are expected to disperse first. If costs of dispersal increase with dispersal distance, dominant juveniles are expected to disperse shorter distances. Alternately, if there are advantages to long-distance dispersal, then dominants, which are in better condition, should disperse further than subordinates. We examined effects of social rank on the timing and distance (to wintering area) of dispersal movements by juvenile western screech-owls, Otus kennicottii, in southwestern Idaho. Based on observations of aggressive interactions made using video cameras attached to nestboxes, we assigned dominance ranks to nestlings within nine broods. We radiotracked young throughout the postfledging period to determine order of dispersal, and we located them after leaving their natal areas to determine distances to apparent overwintering areas. In six of seven broods, for which dispersal information could be recorded, the most dominant juvenile dispersed first. Moreover, in five of seven broods, the least dominant individual was the last individual to disperse, and the order of dispersal matched the dominance hierarchy in four of seven broods. In contrast, social status did not affect postfledging dispersal distance. We conclude that social dominance relationships influenced the timing of dispersal in juvenile western screech-owls but not distance travelled to overwinter sites. Copyright 1999 The Association for the Study of Animal Behaviour.  相似文献   

5.
We studied the post-juvenile dispersal of 18 radiotagged juvenile Hazel Grouse Bonasa bonasia (14 males, four females) in an expanding population in the southeastern French Alps between 1998 and 2001. The mean dispersal distances between the capture sites of juveniles in September–October and the centre of the home range in the following spring was 4 km for males (range 0.1–24.9 km) and 2 km for females (range 0.2–5.6 km). The distances recorded for two long-dispersing males (15 and 24.9 km) are greater than those reported to date for Hazel Grouse. Using our radiotracking data, we interpret the pattern of range expansion that has been occurring since the 1950s around our study area. Barriers to dispersal included rocky ground and other alpine habitats above 2000 m and over 1 km wide, but Hazel Grouse did cross open agricultural land at lower elevation. Two patterns of dispersal movements were recognized in juveniles: erratic movements that led to settlement on or near the natal site, and direct movements to a new range relatively far from the natal area. We discuss the adaptive consequences of these different behaviour patterns.  相似文献   

6.
Many populations of long‐distance migrants are declining and there is increasing evidence that declines may be caused by factors operating outside the breeding season. Among the four vulture species breeding in the western Palaearctic, the species showing the steepest population decline, the Egyptian Vulture Neophron percnopterus, is a long‐distance migrant wintering in Africa. However, the flyways and wintering areas of the species are only known for some populations, and without knowledge of where mortality occurs, effective conservation management is not possible. We tracked 19 juvenile Egyptian Vultures from the declining breeding population on the Balkan Peninsula between 2010 and 2014 to estimate survival and identify important migratory routes and wintering areas for this species. Mortality during the first autumn migration was high (monthly survival probability 0.75) but mortality during migration was exclusively associated with suboptimal navigation. All birds from western breeding areas and three birds from central and eastern breeding areas attempted to fly south over the Mediterranean Sea, but only one in 10 birds survived this route, probably due to stronger tailwind. All eight birds using the migratory route via Turkey and the Middle East successfully completed their first autumn migration. Of 14 individual and environmental variables examined to explain why juvenile birds did or did not successfully complete their first migration, the natal origin of the bird was the most influential. We speculate that in a declining population with fewer experienced adults, an increasing proportion of juvenile birds are forced to migrate without conspecific guidance, leading to high mortality as a consequence of following sub‐optimal migratory routes. Juvenile Egyptian Vultures wintered across a vast range of the Sahel and eastern Africa, and had large movement ranges with core use areas at intermediate elevations in savannah, cropland or desert. Two birds were shot in Africa, where several significant threats exist for vultures at continental scales. Given the broad distribution of the birds and threats, effective conservation in Africa will be challenging and will require long‐term investment. We recommend that in the short term, more efficient conservation could target narrow migration corridors in southern Turkey and the Middle East, and known congregation sites in African wintering areas.  相似文献   

7.
Capsule Natal dispersal was rapid and distances were short. Winter ranging and breeding dispersal were limited. Few birds undertook large movements.

Aims To investigate the natal and breeding dispersal of Marsh Tits, including the timing of dispersal movements.

Methods Nestlings, juveniles and adults were ringed and searched for over 4500 ha during summer, autumn–winter, and spring over six years. Dispersal distances were measured as metric distances and multiples of territory widths. Ranging distances were compared with dispersal distances.

Results Median distances of natal dispersal were 2.6 territory widths for males (704.5 m) and 3.1 territory widths for females (1065.0 m). Median distances of breeding dispersal were 0.2 territory widths for males and females (58.6 and 53.1 m respectively). Most natal dispersal was completed soon after independence, with further movement in spring. Breeding dispersal was also detected during these periods. Median ranging distances were short, and some winter floaters were identified.

Conclusion Marsh Tits had short dispersal distances, with most dispersal activity occurring in June. Results suggested that dispersal behaviour was sensitive to habitat fragmentation, resulting in poor settling success outside of the natal wood. Habitat fragmentation may, therefore, be a contributory factor in the decline of the Marsh Tit population in Britain.  相似文献   

8.
In most cooperatively breeding birds the offspring of one sex, usually male, delays dispersal to remain on the natal territory and helps its parents to rear subsequent young. Thus delayed dispersal could be the first step in the evolution of cooperative breeding. We studied natal dispersal in a population of the group-living speckled warbler, Chthonicola sagittata, based on observations of a colour-banded population over 3 years. Unlike other group-living members of the Acanthizinae, all juvenile males in this population dispersed to settle on foreign territories as subordinates, which do not help rear the young. Speckled warblers showed all the life history traits that are thought to result in a saturated habitat and lead to delayed dispersal: they were sedentary, had high adult survival and had a male-biased sex ratio. However, they differed from other acanthizids in occurring at low density (0.18 birds/ha) on large breeding territories (6-12 ha), with a maximum of two males per territory. This may allow subordinates to live on foreign territories yet avoid aggression from dominants. A benefit of dispersal is that it provides an additional route to gaining a breeding vacancy. Dispersers can acquire vacancies on their new territory or on a neighbour's, but incest avoidance would be likely to constrain nondispersing males to neighbours' territories. A model of relative lifetime success showed that the survival benefits of natal philopatry are unlikely to outweigh this benefit of dispersal.  相似文献   

9.
Understanding dispersal and habitat selection behaviours is central to many problems in ecology, evolution and conservation. One factor often hypothesized to influence habitat selection by dispersers is the natal environment experienced by juveniles. Nonetheless, evidence for the effect of natal environment on dispersing, wild vertebrates remains limited. Using 18 years of nesting and mark–resight data across an entire North American geographical range of an endangered bird, the snail kite (Rostrhamus sociabilis), we tested for natal effects on breeding-site selection by dispersers and its consequences for reproductive success and population structure. Dispersing snail kites were more likely to nest in wetlands of the same habitat type (lacustrine or palustrine) as their natal wetland, independent of dispersal distance, but this preference declined with age and if individuals were born during droughts. Importantly, dispersing kites that bred in natal-like habitats had lower nest success and productivity than kites that did not. These behaviours help explain recently described population connectivity and spatial structure across their geographical range and reveal that assortative breeding is occurring, where birds are more likely to breed with individuals born in the same wetland type as their natal habitat. Natal environments can thus have long-term and large-scale effects on populations in nature, even in highly mobile animals.  相似文献   

10.
Natal dispersal and its consequences in Black Grouse Tetrao tetrix   总被引:3,自引:0,他引:3  
Data on dispersal distances of juveniles are important for understanding the genetic structure of populations, population regulation processes and the effects of landscape ecology on metapopulation dynamics. We studied dispersal in juvenile Black Grouse Tetrao tetrix in the French Alps between 1990 and 1998, by radiotracking 39 young grouse captured in August or autumn in a study area of 836 ha. Natal dispersal occurred in two discrete phases, autumn (October) and spring (mid-April to early May), with periods of reduced mobility between. The mean distance travelled by females exceeded that of males in autumn but not in spring. The natal dispersal distance of females was greater than that of males, and resulted in 81% of females leaving the study area to nest 5–29 km from their site of capture. This emigration must have been compensated for by immigrants because the number of hens in the study area increased during the study. Males were more philopatric. By the summer after capture, only 9% had emigrated from the study area. Despite the longer dispersal distances of females, there was no difference in the survival functions of the sexes between the ages of 6 weeks and 13 months.  相似文献   

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