News News

The juvenile dispersal distances of the Spanish imperial eagle

The distribution of juvenile dispersal distances of a territorial long-lived species with deferred maturity, the Spanish imperial eagle, was investigated. A reintroduction program was used as an experimental approach to test predictions of different hypotheses about the distribution of juvenile dispersal distances: competition and wandering behavior. The maximal juvenile dispersal distances of 59 young eagles were determined; (i) 30 wild non-manipulated individuals, and (ii) 29 translocated young under an ad libitum feeding program, released with adults breeding in the area. The competitive displacement hypothesis predicts a leptokurtic distribution of distances in wild non-manipulated young as well as in released young. Under the ‘wandering' hypothesis, however, a leptokurtic distribution is expected in wild young but a normal distribution would be expected in young released, owing to a general improvement in the nutritional status of released young that have been fed ad libitum, as is usual in reintroduction programs. Additionally, a negative relationship between hatching date and dispersal distances is expected in wild young but no relationship in released young under ad libitum feeding. Mean maximum dispersal distances for all the juvenile eagles was 142.8 Km. No differences between sexes were found, nor between populations or between wild and reintroduced young. Wild young distances were not normally distributed, being closer to a Poisson distribution. In contrast, released young with adults (under ad libitum feeding) showed a normal distribution. Wild birds showed a significant negative relationship between dispersal distance and hatching date, with young that hatched late in the season dispersing shorter distances. However, released young under ad libitum feeding showed no significant relationship between hatching date and dispersal distance. These results support the "wandering" hypothesis as the main driver of the distribution of dispersal distances. informacion[at] Ferrer & Morandini (2017) Better nutritional condition changes the distribution of juvenile dispersal distances: an experiment with Spanish imperial eagles. J Avian Biol doi:10.1111/jav.01468
Average (0 Votes)

Latest News Latest News

Geographic isolation, key to the absence of parasites of avian malaria in Cory’s shearwater

The apparent scarcity or absence of blood parasites in some avian groups, such as seabirds, has been related to intrinsic and extrinsic factors including host immunological capacity, host-parasite...

The roles of remote sensing in nature conservation

In this volume, the ability of new technologies, such as drones, camera traps or miniaturized sensors, to enhance our information on habitat condition, species occurrence, invasive species mapping...

UV filters in wild bird eggs

The study shows that UV filters have reached the eggs of Doñana birds, and reveals that OH-derivatives are transferred by the mother to the egg before the lying.