Breeding, Morphology, and Growth of the Endangered Dark-Rumped Petrel

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Abstract
Dark-rumped Petrels (Pterodroma phaeopygia phaeopygia) in the Galapagos archipelago [Pacific Ocean] breed on several islands. Life-history characteristics such as mate and site fidelity, large egg size, long incubation periods, long incubation bouts, and chick growth patterns are similar to those of other procellarids. Adults nest annually, but the timing of breeding is out-of-phase among the islands of Floreana, Santa Cruz, and Santiago. Banding data for 1,500 adults and juveniles indicated that little or no interbreeding occurs among islands. From adult morphological characteristics measured during five years on Floreana and one year on both Santiago and Sant Cruz, we found that on Floreana, adults were sexually monomorphic in all measured characteristics except bill height, and the adults from Floreana tended to be larger in both size and mass than adults from the other two islands. The possibility that each island''s population is distinct should be considered when formulating management plans concerning this species.