Population Estimates and Breeding Biology of the Petrels Pterodroma externa and P. longirostris on Isla Alejandro Selkirk, Juan Fernandez Archipelago
- 1 August 1987
- journal article
- Published by Oxford University Press (OUP) in Ornithological Applications
- Vol. 89 (3) , 581-586
- https://doi.org/10.2307/1368646
Abstract
The Juan Fernandez Petrel (Pterodroma externa externa) and Stejneger's Petrel (P. longirostris) are respectively confined as a breeding race and a breeding species to Isla Alejandro Selkirk in the Juan Fernandez archipelago. The mixed upland colony of the two species was mapped and the density assessed by quadrat methods. The 1985-1986 world breeding population of the two species was estimated as 1,131,000 ± 209,000 pairs, comprising 1,000,000 pairs of P. e. externa and 131,000 pairs of P. longirostris. Predation by introduced cats fell disproportionately on the smaller P. longirostris. Both species bred in the southern summer, laying in late December and early January. Incubation spells were lengthy averaging about 3 weeks. In other respects the petrels' breeding biology was typical of Pterodroma species.Keywords
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