Territorial Behavior and nesting dispersion in Red-Necked Grebes

The Red-necked Grebe (Podiceps grisegena) is a species in which breeding pairs use both overt aggression and ritualistic behavior to defend territories for breeding and feeding. However in some areas, they also breed in colonial groups. The behavior of grebes breeding on a single large lake (2,537 ha), where some breed solitarily and others breed in colonies, was examined. Specifically, I compared the frequency and spatial distribution of behavioral interactions between pairs that had dispersed nests with those breeding in close proximity. Grebes breeding in a colony engaged in more overt behavioral interactions and spent more time conducting platform behavior during pre-nesting than their solitary counterparts. In addition, the locations of ritualized and overt interactions from the nest were greater for solitary breeders. However, grebes breeding in the colony tolerated conspecifics at closer distances which, suggests that those breeding in higher aggregations may expend more energy when dealing with conspecifics.