Population viability and conservation of African Grey Parrots on the island of Príncipe, Gulf of Guinea

Simon Valle


Understanding the conditions under which trade of harvested species is non-detrimental to wild populations is one of the priorities of global biodiversity conservation. Parrots are among the most endangered bird orders in the world, with 37% of the species listed as threatened. The pet trade, together with habitat loss, is considered the main cause of worldwide parrot population declines. Nonetheless, it has been suggested that a controlled harvest can be kept sustainable, and even beneficial to a species’ conservation, if data on its population dynamics were available.
Parrots are long-lived birds which inhabit dense forest habitats, and their crucial life history traits have rarely been described in the wild. Even fundamental measures like population size and density are missing for most species. Parrots nest in natural tree cavities which can easily go overlooked, so critical demographic parameters such as proportion of the population that breeds in a given year are seldom known. Parrot nesting requirements and their importance as a population limiting factor are yet to be fully understood. Parrots are ‘slow’ breeders with a high nestling mortality, but specific nest productivity studies are rare. Furthermore, reliable mark and re-sighting studies of parrots virtually unknown outside of Australia, so juvenile and adult survivorship can only be guessed at. Finally, although harvest is a widespread and lucrative activity, the magnitude of the annual harvest on a given population is seldom quantified reliably. Thus, population dynamics of parrot species are still largely unknown, although it would be crucial to understand the effects of pet trade and habitat disruption on their population viability.
The African Grey Parrot Psittacus erithacus (henceforth ‘AGP’) is one of the most popular avian pets due to its longevity and mimicry ability. AGP is the object of a US$18 million/year trade business, which takes tens of thousands of individuals from the wild, but to date no study has assessed the impact of such harvest on wild populations. Thus, there is an opportunity to generate crucial information on AGP ecology and conservation status. The best information available to date suggests that this species is in decline in most of its vast distribution range. Príncipe is a small island (136 km2) in the Gulf of Guinea (West Africa) which is home to a large population of AGP which has a long tradition of parrot harvesting and trade. Hence, Príncipe offers a unique opportunity to study the population dynamics of this species along with the effects of harvest and to use our results to inform management of traded populations elsewhere in AGP’s range. 

This PhD research will thus contribute to our understanding of the population dynamics and conservation biology of AGPs on the island of Príncipe but will provide a framework within which the sustainability of other traded parrot populations elsewhere can be assessed.


 1.    To estimate the population size and density of AGP in a range of natural and anthropogenic habitats across Príncipe.

2.    To examine the nesting requirements of AGP, the effect of habitat alteration on nest site availability, and to estimate nest density and proportion of the population that breeds in a given year.

3.    To estimate nest productivity and nestling mortality in a range of habitats, and link these to habitat quality.

4.    To estimate juvenile and adult survival and to investigate causes of mortality.

5.    To assess current and historic magnitude of parrot harvest and its impact on Príncipe’s society and economy

6.    To build demographic models to investigate the effects of bird trade and habitat disturbance on the AGP population on Príncipe, and test their applicability to mainland populations of AGP and to other parrot species.

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