The Hybrid Skua: A Southern Ocean Enigma

• Published in: The Wilson bulletin (Wilson Ornithological Society) 1988-09, Vol.100 (3), p.345-356
• Main Author: Parmelee, David F.
• Format: Article
• Language: English
• Subjects: Aves; Biological and medical sciences; Bird banding; Bird nesting; Breeding; Eggs; Female animals; Fundamental and applied biological sciences. Psychology; Hybridity; Male animals; Mating behavior; Nesting sites; Penguins; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0043-5643; 2162-5204

Mixed pairs of South Polar Skuas (Catharacta maccormicki) and Brown Skuas (C. lonnbergi) were banded and observed during a 9-year study within a narrow zone of sympatry near the Antarctic Peninsula. A history of their territorial, mate, and other preferences disclosed that mixed pairs usually, but not invariably, reside near penguin colonies; male maccormicki usually, but not invariably, pair with female lonnbergi; some mixed pairs remained faithful, whereas members of others readily remated with the same or different species; nesting success in mixed pairs paralleled nesting success in maccormicki, indicating a major role of the male in securing food for the female before egg laying. Although hybrids resulting from mixed matings resembled lonnbergi in appearance, their mating, feeding, and migratory behavior resembled those of maccormicki. At least some F1hybrids were fertile, but matings between maccormicki and lonnbergi were less than expected by chance alone, and the two skuas were considered close but separate species. Field identification of hybrids was extremely difficult and likely will confuse observers along the migratory routes.