A B S T R A C TPopulation models have played a chief role informing management decisions for the endangered Bonelli's eagle (Aquila fasciata) in Spain. In this paper, we incorporate spatial structure and stochasticity in the construction of individual-based metapopulation models, and use these models to explore the effects of possible management actions on the persistence of the species in Spain. To build the models we used data on seven subpopulations that have experienced different trends in the last decades, and we introduced new estimates of pre-adult survival rate. The elasticity analysis of our models showed that when the interchange of individuals among sub-populations is taken into account, preadult mortality plays the key role in determining the overall population trend. This is in contrast to what it has been suggested by previous demographic models that modelled local populations as isolated. Specifically, a 20% decrease in pre-adult mortality during the first two years of life was enough for the stabilization of the metapopulation (i.e., k P 1.0). However, neither a similar decrease in the values of adult mortality, nor an increase in the percentage of breeders, modified the declining trend of our model metapopulation. This reinforces the idea that to ensure the long-term persistence of the species in Spain, management actions should aim at minimizing pre-adult mortality. These include locating and protecting the areas used by juvenile Bonelli's eagles (e.g., temporary settlements), minimizing the risk of electrocution in power lines, and preventing human persecution. Introduction 53During the last decades there has been an increasing aware-54 ness of the roles of space and environmental and demo-55 graphic stochasticity in populations' dynamics (e.g., Tilman 56and Kareiva, 1997;Hanski, 1999;Lande et al., 2003), with com-57 puter simulations playing a key role in the analysis of the ef-58 fects of those factors on populations' trajectories 59 (Lindenmayer et al., 1995;Hanski, 1999). For stage-structured 60 populations an alternative to simulations for projecting pop-61 ulation trajectories is the use of matrix population models 62 (e.g., Caswell, 2001). These matrix population models have 63 been influential in the derivation of management recommen-64 dations for many endangered species (e.g., Crouse et al., 1987; 0006-3207/$ -see front matter Ó 2008 Published by Elsevier Ltd. doi:10.1016/j.biocon.2008.01.011 * Corresponding author: Address: Estació n Bioló gica Terra Natura, CIBIO -Fundació n Terra Natura, Universidad de Alicante, Apdo. 99 E, 03080 Alicante, Spain. Tel.: +34 965903400x3202; fax: +34 963543670. Q2E-mail addresses: Pascual.Lopez@uv.es, lopez.pascual@gmail.com (P. Ló pez-Ló pez). and use these models to explore the effects of possible man-107 agement actions on the persistence of the species in Spain.a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c 108 Methods 109We used the Vortex simulations software (Lacy, 1993(Lacy, , 2000 110 Lacy et al., 2005) to develop model...

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 postnestling 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.

Here we provide the first assessment of the accuracy of lightweight satellite transmitters (,80 g) under actual operating conditions and the performance of the Argos system in southern Europe. To estimate transmitter accuracy we used transmitters equipped with a Global Positioning System (GPS) and compared the location estimates provided by Argos with the estimates provided by the GPS. Using the 68th percentile to define the accuracy of locations estimates, observed accuracy was 4 km for Location Class (LC) 1, 15 km for LC 0, 20 km for LC A, and 59 km for LC B, which is in line with estimates reported by other authors. Yet, the error of the remaining 32% of the data ranged between 4 km and 11 km, 15 km and 217 km, 20 km and 145 km, and 59 km and 493 km, respectively, suggesting that using the 68th percentile to estimate accuracies might give misleading confidence on the accuracy of location estimates. Using the 90th percentile is probably more appropriate. Less than 10% of the locations we obtained corresponded to the more accurate LCs (3, 2, and 1), with Argos failing to provide a position estimate in 45% of the attempts. The low number of high-quality location estimates is likely a consequence of the electromagnetic interference reported for our study area, rather than a defect of the Platform Transmitter Terminals (PTTs), which under good conditions of signal reception seem to be as reliable as heavier ones. The recent advent of lightweight GPS transmitters overrides most of these problems. Yet, whereas the smallest Argos-GPS PTTs weigh 30 g, which restricts their use to animals weighting .1,000 g, conventional PTTs can be as small as 9.5 g, allowing their use with animals weighting