Habitat Constraints and Spatial Bias in Seabird Colony Distributions

• Published in: Ecography (Copenhagen) Vol. 23; no. 5; pp. 575 - 578
• Main Authors: Forbes, L. Scott, Jajam, Martin, Kaiser, Gary W.
• Format: Journal Article
• Language: English
• Published: Oxford Munksgaard International Publishers 01.10.2000; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Aves; Biological and medical sciences; Breeding; Burrows; Canada, British Columbia; Cerorhinca monocerata; Colonies; Fundamental and applied biological sciences. Psychology; Habitats; Marine; Nesting sites; Perceptual localization; Population ecology; Ptychoramphus aleuticus; Random allocation; Sea birds; Synthliboramphus antiquus; Vertebrata; Wildlife habitats; Canada; Pacific Ocean; North America; America; INE, Canada, British Columbia; Nesting site; Interspecific comparison; Trophic factor; Population number; Environmental factor; Habitat selection; Island; Marine environment; Vertebrata; Spatial distribution; Intraspecific competition; Colony; Aves; Food supply
• ISSN: 0906-7590; 1600-0587
• DOI: 10.1034/j.1600-0587.2000.230508.x

What governs the size and location of seabird colonies has long intrigued population ecologists. Previous analysis of the distribution of colonies of four European seabirds revealed a spatial bias - large colonies occurred farther apart than expected by chance alone - suggesting that intraspecific competition for food supplies during breeding may regulate colony size. Here we use computer intensive statistics to show that a similar spatial bias exists in three burrow-nesting seabirds - Cassin's auklet Ptychoramphus aleuticus, rhinoceros auklet Cerorhinca monocerata, and ancient murrelet Synthliboramphus antiquus - nesting off the Pacific coast of Canada. Local habitat constraints explain much of the existing spatial bias: large colonies cannot fit on small islands, and large islands suitable for colonies tended to occur far apart. However, a residual spatial bias still remained for ancient murrelets and Cassin's auklets (but not rhinoceros auklets) after habitat constraints are built into the analysis, for which intraspecific food competition remains a plausible explanation.