Passive Interference Competition by Glaucous-Winged Gulls on Black-Legged Kittiwakes: A Cost of Feeding in Flocks
Maniscalco JM, Ostrand WD, Suryan RM, Irons DB. 2001. Passive Interference Competition by Glaucous-Winged Gulls on Black-Legged Kittiwakes: A Cost of Feeding in Flocks. The Condor. 103(3):616-619
We analyzed data from two independent studies of foraging Black-legged Kittiwakes (Rissa tridactyla) in Prince William Sound, Alaska. Our purpose was to determine if Glaucous-winged Gulls (Larus glaucescens) hindered prey capture by kittiwakes. At tightly aggregated feeding flocks, gulls remained on the water directly over the prey and foraged by making brief hop-plunges or surface-seizes. Kittiwakes, in contrast, fed by diving from the air into open spots in the flock or around its periphery. Data from both studies indicated that kittiwakes made fewer feeding attempts in flocks that had greater numbers of gills. However, kittiwake success rate per feeding attempt did not change as the number of gulls increased. Kittiwakes were more likely to avoid flocks that had a greater number of Glaucous-winged Gulls. Gulls successfully pirated less than 1% of fish captured by kittiwakes. Our findings suggest that passive interference may be costly for smaller birds that feed in multispecies feeding flocks.
- Type
- Journal Article
- Authors
- Maniscalco, John; Ostrand, William; Suryan, Robert; Irons, David
- Units
- GLBA , KLGO , SEAN , SITK
- Keywords
- Black-legged Kittiwake, Fish SCHOOLS, Glaucous-winged Gall, interspecific competition, multispecies feeding flocks, Murrelets, passive interference competition, Prince William Sound, Roseate terns, Seabirds, Selection, Success