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José María Gil-Sánchez

Bio: José María Gil-Sánchez is an academic researcher from University of Granada. The author has contributed to research in topics: Population & Bonelli's eagle. The author has an hindex of 20, co-authored 50 publications receiving 1111 citations. Previous affiliations of José María Gil-Sánchez include Junta of Andalusia & Universidad Miguel Hernández de Elche.


Papers
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Journal ArticleDOI
01 Mar 2006-Oikos
TL;DR: Assessing the relative contribution of habitat heterogeneity and bird quality (in terms of age) on the productivity of sympatric golden Aquila chrysaetos and Bonelli's eagles Hieraaetus fasciatus found temporal changes in bird quality combined with intra- and interspecific competition explained variability in territory productivity rather than habitat heterogeneity among territories per se.
Abstract: Density-dependent breeding performance due to habitat heterogeneity has been shown to regulate populations of territorial species, since the progressive occupation of low quality territories as breeding density increases may cause a decline in the mean per capita fecundity of a population while variation in fecundity increases. Although the preemptive use of sites may relegate low quality individuals to sites of progressively lower suitability, few studies on density dependence have tried to separate the effects of territory quality from individual quality, and none have simultaneously considered the effects of heterospecific competitors. Using two long-term monitored populations, we assessed the relative contribution of habitat heterogeneity and bird quality (in terms of age) on the productivity of sympatric golden Aquila chrysaetos and Bonelli’s eagles Hieraaetus fasciatus under different scenarios of intra- and inter-specific competition. Productivity (number of offspring fledged) varied among territories and average annual productivity was negatively related to its variability in both species and populations, thus giving some support to the habitat heterogeneity hypothesis. However, the effect of habitat heterogeneity on productivity became non-significant when parental age and local density estimators were included in multivariate analyses. Therefore, temporal changes in bird quality (age) combined with intra- and interspecific competition explained variability in territory productivity rather than habitat heterogeneity among territories per se. The recruitment of subadult breeders, a surrogate of mortality in eagles, strongly varied among territories. Habitat heterogeneity in productivity may thus arise not because sites differ in suitability for reproduction but because of differences in factors affecting survival. Territories associated with high mortality risks have a higher probability of being occupied by young birds, whose lower quality, interacting with the density competitors, leads to a reduction of productivity. Sitedependent variability in adult survival and interspecific competition may be extensive, but so far largely overlooked, factors to be seriously considered for the site-dependent population regulation framework.

111 citations

Journal ArticleDOI
TL;DR: The role of this healthy subpopulation in an Iberian metapopulation context is discussed, and it is proposed that the potential interference of golden eagles should be taken into account when designing management strategies for Bonelli's eagles.

76 citations

Journal ArticleDOI
TL;DR: Consejeŕia de Medio Ambiente de the Junta de Andalucia, c/ Doctor Eduardo Garcia-Trivino Lopez, 15.
Abstract: MIGUEL A. SIMON,∗ JOSE M. GIL-SANCHEZ,† GEMA RUIZ,† GERMAN GARROTE,† EMIL B. MCCAIN,‡§ LEONARDO FERNANDEZ,† MARCOS LOPEZ-PARRA,† EVA ROJAS,† RAFAEL ARENAS-ROJAS,† TERESA DEL REY,† MARIBEL GARCIA-TARDIO,† AND GUILLERMO LOPEZ∗∗† ∗Consejeŕia de Medio Ambiente de la Junta de Andalucia. c/ Doctor Eduardo Garcia-Trivino Lopez, 15. 23009 Jaen, Spain †Agencia de Medio Ambiente y Agua de Andalucia. c/ Johan Gutenberg s/n, Isla de la Cartuja 41092 Seville, Spain ‡Iberus Medio Ambiente S.L., Avda. Granada 35 PI: 1 Pt: A. 23003 Jaen, Spain §Parque Natural Sierra de Andujar. Cercado del Cipres. Camino de los Rubiales s/n 23740 Andujar (Jaen), Spain

74 citations

Journal ArticleDOI
TL;DR: The former and present distribution of white clawed crayfish (Austropotamobius pallipes) in the province of Granada (southern Spain) is studied in this article.

74 citations

Journal ArticleDOI
TL;DR: In this article, the authors performed a population viability analysis of the whole western European population (France, Portugal, and Spain) of the endangered Bonelli's Eagle (Aquila fasciata) and explored the consequences of uncertainty in population processes and parameters on PVA predictions.
Abstract: Population viability analysis (PVA) has become a basic tool of current conservation practice. However, if not accounted for properly, the uncertainties inherent to PVA predictions can decrease the reliability of this type of analysis. In the present study, we performed a PVA of the whole western European population (France, Portugal, and Spain) of the endangered Bonelli's Eagle (Aquila fasciata), in which we thoroughly explored the consequences of uncertainty in population processes and parameters on PVA predictions. First, we estimated key vital rates (survival, fertility, recruitment, and dispersal rates) using monitoring, ringing, and bibliographic data from the period 1990-2009 from 12 populations found throughout the studied geographic range. Second, we evaluated the uncertainty about model structure (i.e., the assumed processes that govern individual fates and population dynamics) by comparing the observed growth rates of the studied populations with model predictions for the same period. Third, using the model structures suggested in the previous step, we assessed the viability of both the local populations and the overall population. Finally, we analyzed the effects of model and parameter uncertainty on PVA predictions. Our results strongly support the idea that all local populations in western Europe belong to a single, spatially structured population operating as a source- sink system, whereby the populations in the south of the Iberian Peninsula act as sources and, thanks to dispersal, sustain all other local populations, which would otherwise decline. Predictions regarding population dynamics varied considerably, and models assuming more constrained dispersal predicted more pessimistic population trends than models assuming greater dispersal. Model predictions accounting for parameter uncertainty revealed a marked increase in the risk of population declines over the next 50 years. Sensitivity analyses indicated that adult and pre-adult survival are the chief vital rates regulating these populations, and thus, the conservation efforts aimed at improving these survival rates should be strengthened in order to guarantee the long-term viability of the European populations of this endangered species. Overall, the study provides a framework for the implementation of multi-site PVAs and highlights the importance of dispersal processes in shaping the population dynamics of long-lived birds distributed across heterogeneous landscapes.

71 citations


Cited by
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TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

14,171 citations

30 Apr 1984
TL;DR: A review of the literature on optimal foraging can be found in this article, with a focus on the theoretical developments and the data that permit tests of the predictions, and the authors conclude that the simple models so far formulated are supported by available data and that they are optimistic about the value both now and in the future.
Abstract: Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

2,709 citations

Journal Article
TL;DR: In this paper, a test based on two conserved CHD (chromo-helicase-DNA-binding) genes that are located on the avian sex chromosomes of all birds, with the possible exception of the ratites (ostriches, etc.).

2,554 citations