Title
Breeding biology of royal and cayenne terns at a mixed-species colony in Patagonia
Author(s)
Quintana F., Yorio P.
Published
1997
Publisher
Wilson Bulletin
Abstract
We studied the breeding biology of Royal (Sterna maxima) and Cayenne terns (S. eurygnatha) at Punta Leon, Patagonia, during 1989-93. In all years, both species bred in a single colony with their nests intermingled. Colony size varied between 1,150 and 1,830 pairs. Colony formation occurred during the first or second week of October. Nesting densities were relatively high (9.8 to 11.1 nests/m2). Both species started to lay eggs during the second and third week of October in all years. During 1993, clutch size for Royal and Cayenne terns was 1.3 ± 0.5 and 1.1 ± 0.3, respectively. The length of the incubation period was 25.7 ± 0.9 and 29.1 ± 3 days for Royal and Cayenne terns, respectively. During 1993, hatching success was 0.72 ± 0.34 and 0.68 ± 0.42 chicks per nest for Royal and Cayenne terns, respectively. Egg losses (45.3%) were mainly from predation. First-hatched chicks were observed during mid November. Chick survival to 10 days of age was 90% and 66.7% for Royal and Cayenne terns, respectively. At approximately 20 days of age, some tern chicks started to abandon the colony to form creches at the beach. Royal and Cayenne terns generally fed out of sight from the colony and preyed upon the same species, including Odontestes spp., Stromateus brasiliensis, Engraulis anchoita, and Sprattus fueguensis.
Keywords
Engraulis anchoita; Odontestes; Sprattus fueguensis; Sterna eurygnatha; Sterna maxima; Stromateus brasiliensis
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