Regulation of incubation behavior in Black Brant

We assessed the influence of climatic, environmental,. and biological facto rs on nest attentiveness of female Black Brant (Branta bernicla nigricans). Within females, nest attentiveness varied significantly with time of day, rainfall, ambient temperature, incubation day, and (incubation day)(2). We examined variation among females in individual investment in reproduction b y comparing the amounts of nutrients invested in the clutch with those inve sted in incubation. We compared nest attentiveness with the amount of nutri ent reserves available to test the hypothesis that a trade-off exists betwe en nutrient investment in eggs and investment in incubation. Among females, nest attentiveness was lower in 1992 ((x) over bar = 82%) than in 1993 ((x ) over bar = 87%) and increased with clutch volume and mass. Our results sh ow that environmental conditions influence incubation behavior in Black Bra nt. We detected a trade-off between investment in eggs and nest attentivene ss, but the results are also consistent with the hypothesis that females va ry in individual quality and this variation influences egg production as we ll as incubation.