High survival rate of a critically endangered species, the Azores Bullfinch Pyrrhula murina, as a contribution to population recovery |
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Authors: | David Monticelli Ricardo Ceia Ruben Heleno Hugo Laborda Sergio Timóteo Daniel Jare?o Geoff M Hilton and Jaime A Ramos |
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Institution: | (1) Laboratory of Tropical and Subtropical Forestry, Unit of Forest and Nature Management, Gembloux Agricultural University, 2 Passage des D?port?s, 5030 Gembloux, Belgium;(2) Sociedade Portuguesa para o Estudo das Aves, 105 Av. da Liberdade, 1250-140 Lisbon, Portugal;(3) School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, UK;(4) Wildfowl & Wetlands Trust (WWT), Slimbridge, Glos, GL2 7BT, UK;(5) Institute of Marine Research (IMAR/CMA), Department of Life Sciences, University of Coimbra, Apartado 3046, 3001-401 Coimbra, Portugal |
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Abstract: | This paper reports analyses of a capture–mark–recapture (CMR) dataset of 149 Azores Bullfinches ringed on S?o Miguel island
(Azores) between 2005 and 2007, and recaptured–resighted on a monthly basis over a 4-year period (2005–2008) throughout their
breeding range. We examined the effect of time, age (adults vs. juveniles), gender (adult males and females), and environmental
covariates (temperature, rainfall, NAO index) on survival probabilities. The modelling found a high and constant monthly survival
probability (mean ± SE) estimated at 0.96 ± 0.01, similar between both adults and juveniles and independent of environmental
conditions and gender. These findings agree with expectations from island-based life-history theory where relatively mild
conditions and lack of predators should favour high survival rates to compensate for the low reproductive output. The annual
survival rate was estimated at 0.62, which was also consistent with this pattern when compared with survival estimates of
mainland bullfinch and passerine species on other subtropical islands obtained in similar CMR studies. Based on a canonical
estimator, the size of the studied population (mean ± SE) was estimated at 1608 ± 326 individuals. Given that the population
size was only around 120–400 individuals in the early 1990s, we suggest that the high survival probabilities currently applying
to this critically endangered species may have substantially contributed to the recent recovery of this population. Future
research studies on the species’ demography should continue to monitor survival in order to measure the effect of management
interventions currently taking place within the range of the Azores Bullfinch, including the restoration of the biodiversity
rich laurel forest, but also focusing on nest success, which is important for understanding population dynamics. |
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