Spatial and seasonal variation in abundance within an insular grey parrot population

Valle, S, Collar, NJ, Harris, WE and Marsden, SJ (2017) Spatial and seasonal variation in abundance within an insular grey parrot population. African Journal of Ecology. ISSN 0141-6707

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Abstract

© 2017 John Wiley & Sons Ltd. Populations of Psittacidae are endangered by habitat loss and the international pet market. The grey parrot (Psittacus erithacus) is among the most traded species, yet little is known about densities and their variability in time and space. The population of grey parrots on the island of Príncipe (Gulf of Guinea) was estimated with distance sampling, in both pre- and postbreeding seasons. Abundance was related to a range of habitat features using generalized additive models. Densities averaged 48 ± 3 (SE) individuals km-2 in the prebreeding and 59 ± 4 in the postbreeding season, both extremely high compared to elsewhere in Africa and to other parrot species. Despite a population of 6000-8000 individuals over only 139 km2, parrots were patchily distributed, being unrecorded in ~25% of surveyed areas. Abundance varied seasonally, with densities being significantly higher in secondary compared to primary forest in the post- but not in the prebreeding season. Abundance was most tied to the presence of nest-tree species prior to breeding and to feeding-tree species and lightly sloping ground after breeding. These results highlight the need to preserve a matrix of habitat types to provide resources for parrots across seasons and ensure that surveys recognize seasonality in habitat use as a potential bias.