Pseudo-egg and exotic egg adoption by Kelp Gulls Larus dominicanus vetula

Abstract

Ground-nesting birds, particularly larids, are known to include a variety of items in their nests as pseudo-eggs, as well as to adopt the eggs of conspecifics or other species. Three hypotheses have been put forward to explain this phenomenon: incubation stimulus, mistaken-food, and mistaken-egg hypotheses. Of 382 Kelp Gull Larus dominicanus vetula nests monitored during 2013/14, 11 instances of pseudo-egg (mostly driftwood and beef/ lamb bones), and one instance of exotic egg, adoption were recorded. A combination of all three hypotheses was attributed for the adoption of pseudo-eggs, whereas the exotic egg adoption could have been due to the need for incubation stimulus or a case of mistaken food.

Keywords: incubation stimulus, mistaken-egg hypothesis, mistaken-food hypothesis