Breeding performance, age effects and territory occupancy in a Bonelli's Eagle Hieraaetus fasciatus population

Jose A. Martinez, Jose F. Calvo, Jose E. Martinez, Inigo Zuberogoitia, Jabi Zabala, Stephen M. Redpath

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Bonelli's Eagle Hieraaetus fasciatus is one of the most endangered birds of prey in Europe. Despite mounting interest and research, several questions regarding the conservation implications of territory occupancy and site-dependent population regulation remain insufficiently explored for this species. Here, we report on a 12-year study of the territorial structure of a Bonelli's Eagle population in southeastern Spain. No signals of population decline were found in the breeding population, as mean annual productivity was stable and the presence of mixed-age pairs in the population decreased with the years. However, the average proportion of subadults occupying territories was larger than that observed in other Spanish populations. Contrary to the predictions of a despotic distribution model, we found no significant relationship between occupancy rates and breeding parameters. Our results showed significant variations in productivity attributable to differences in the quality of individuals (i.e. mixed versus adult pairs), but no variability among territories per se (i.e. caused by habitat heterogeneity). Moreover, coexistence with intraguild species did not have any significant effect on productivity, although the proximity of Eagle Owls Bubo bubo affected the occupation rate of territories. Finally, our population does not appear to experience site-dependent population regulation, as a positive relation between mean annual productivity and density was found. The threat posed by changes in land use in the study area leads us to suggest that strict protection of current territories is necessary to ensure population persistence, and we suggest that a significant population increase is only likely if new or deserted territories become available.

Original languageEnglish
Pages (from-to)223-233
Number of pages11
JournalIbis
Volume150
Issue number2
Early online date27 Nov 2007
DOIs
Publication statusPublished - Apr 2008

Fingerprint

reproductive performance
breeding
population regulation
productivity
breeding population
population decline
Bubo
coexistence
occupation
effect
Aquila fasciata
persistence
birds of prey
land use
land use change
endangered species
population growth
habitat
prediction
Spain

Keywords

  • ideal despotic distribution
  • intraguild predation
  • inverse density dependence
  • population regulation
  • territory quality

Cite this

Breeding performance, age effects and territory occupancy in a Bonelli's Eagle Hieraaetus fasciatus population. / Martinez, Jose A.; Calvo, Jose F.; Martinez, Jose E.; Zuberogoitia, Inigo; Zabala, Jabi; Redpath, Stephen M.

In: Ibis, Vol. 150, No. 2, 04.2008, p. 223-233.

Research output: Contribution to journalArticle

Martinez, Jose A. ; Calvo, Jose F. ; Martinez, Jose E. ; Zuberogoitia, Inigo ; Zabala, Jabi ; Redpath, Stephen M. / Breeding performance, age effects and territory occupancy in a Bonelli's Eagle Hieraaetus fasciatus population. In: Ibis. 2008 ; Vol. 150, No. 2. pp. 223-233.
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