Should I Stay or Should I Go: Influences on Roseate Terns' (Sterna dougallii) Decisions to Move the Chicks

Abstract

In this study, we investigated the relative influence of habitat variables on the decision by Sterna dougallii (Roseate Tern) parents to move from (movers) or to stay at (stayers) the nest after chick hatch. At Country Island, NS, Canada, 75% of the 21 Roseate Tern breeding pairs in this study were movers. Using a model-selection approach, we found that the chicks were more likely to be moved from nest sites in cobble beach habitat with low vegetation height and high nest densities of congener terns. However, differences in reproductive parameters among movers and stayers were not statistically significant. Though we could not establish whether moving the chicks or staying were adaptive strategies, we provide firm evidence that Roseate Tern chicks are moved to areas of lower tern densities. Chicks move further away from other terns as they age, perhaps as a mechanism to avoid kleptoparasitism as their nutritional requirements increase. Based on our findings, Roseate Terns appear more likely to rear their chicks to fledging at the original nest site when nest densities of other tern species are low (≤0.02 nests/m2) in highly vegetated areas. Thus, to enhance Roseate Tern productivity in places where they are endangered, such as Atlantic Canada, we suggest that species recovery programs place artificial nest cover, e.g., next boxes and wooden logs, in areas with potential for taller vegetation growth that are suboptimal nesting habitat for S. paradisaea (Arctic Tern)and S. hirundo (Common Tern).