title: Using Africa's protected area network to estimate the global population of a threatened and declining species: a case study of the Critically Endangered White-headed Vulture Trigonoceps occipitalis.
abstract: The White-headed Vulture Trigonoceps occipitalis (WhV) is uncommon and largely restricted to protected areas across its range in sub-Saharan Africa. We used the World Database on Protected Areas to identify protected areas (PAs) likely to contain White-headed Vultures. Vulture occurrence on road transects in Southern, East, and West Africa was adjusted to nests per km(2) using data from areas with known numbers of nests and corresponding road transect data. Nest density was used to calculate the number of WhV nests within identified PAs and from there extrapolated to estimate the global population. Across a fragmented range, 400 PAs are estimated to contain 1893 WhV nests. Eastern Africa is estimated to contain 721 nests, Central Africa 548 nests, Southern Africa 468 nests, and West Africa 156 nests. Including immature and nonbreeding birds, and accounting for data deficient PAs, the estimated global population is 5475 - 5493 birds. The identified distribution highlights are alarming: over 78% (n = 313) of identified PAs contain fewer than five nests. A further 17% (n = 68) of PAs contain 5 - 20 nests and 4% (n = 14) of identified PAs are estimated to contain >20 nests. Just 1% (n = 5) of PAs are estimated to contain >40 nests; none is located in West Africa. Whilst ranging behavior of WhVs is currently unknown, 35% of PAs large enough to hold >20 nests are isolated by more than 100 km from other PAs. Spatially discrete and unpredictable mortality events such as poisoning pose major threats to small localized vulture populations and will accelerate ongoing local extinctions. Apart from reducing the threat of poisoning events, conservation actions promoting linkages between protected areas should be pursued. Identifying potential areas for assisted re-establishment via translocation offers the potential to expand the range of this species and alleviate risk.
authors.affiliation: Hawk Conservancy Trust Andover Hampshire SP11 8DY UK; Centre for Wildlife Assessment and Conservation School of Biological Sciences University of Reading Berkshire RG6 6AS UK.
authors.forename: Campbell
authors.initials: C
authors.lastname: Murn
authors.affiliation: Department of Forest Resources and Wildlife Management National University of Science and Technology Bulawayo Zimbabwe.
authors.forename: Peter
authors.initials: P
authors.lastname: Mundy
authors.affiliation: Ornithology Section Department of Zoology National Museums of Kenya P.O Box 40658 Nairobi 00100 Kenya; The Peregrine Fund 5688 West Flying Hawk Lane Boise Idaho 83709.
authors.forename: Munir Z
authors.initials: MZ
authors.lastname: Virani
authors.affiliation: BirdLife Botswana PO Box 26691 Gaborone Botswana.
authors.forename: Wendy D
authors.initials: WD
authors.lastname: Borello
authors.affiliation: Centre for Wildlife Assessment and Conservation School of Biological Sciences University of Reading Berkshire RG6 6AS UK.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Holloway
authors.affiliation: Rue de la Rivière 10220 Rouilly - Sacey France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Thiollay
keywords: Decline; Trigonoceps occipitalis; White‐headed Vulture; nest densities; protected areas