PARENT SESSION
Oral Session #64: Avian Ecology. Presiding: P. Warren.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Hall of Ideas I.
Modeling the impact of time of first clutch initiation: new directions to an old problem?
Nagy, Laura1, Holmes, Richard1, 1
ABSTRACT- Current dogma assumes individuals that breed earlier produce more young because they have more time available in the breeding season. To test this assumption, I developed a model parameterized with 4 years of reproductive data from Black-throated Blue Warblers (Dendroica caerulescens). The goals were 1) to predict the number of young fledged per pair based on clutch initiation date, 2) to determine the implications of breeding late, 3) to examine the sensitivity of the parameters in the model and to 4) apply different recruitment curves to the results. Parameters included probability of nest survival, probability of renesting, number of days until renesting, and, if a nest failed, number of days until nest failure. Results showed a significant decline in number of young fledged/pair/year as date of first clutch initiation increased (P<0.0001). The model was most sensitive to the probability of renesting, which decreased with time, and least sensitive to number of days until renesting. The latter result suggests that length of time, per se, may not be a critical factor. Instead, some measure indirectly correlated with time (i.e., physiological change of the bird, availability of resources) may reduce the probability of a bird renesting, causing the decline in reproductive output relative to the first clutch initiation.
KEY WORDS: Warbler, seasonal, modelling, double-brood