Meeting Abstract

P1.151  Tuesday, Jan. 4  “Cream skimming” versus “best of a bad situation:” Are all reproductive opportunists alike? HAHN, T.P.; CORNELIUS, J.M.; WATTS, H.E.*; KELSEY, T.R.; Univ. of California, Davis; Max Planck Inst. for Ornithology; Loyola Marymount Univ.; National Audubon Society hwatts1@lmu.edu

Birds time breeding to match occurrence of favorable conditions. For many this means seasonal breeding. In a few cases nearly continuous breeding is possible, and in others unpredictable conditions favor flexible, or “opportunistic,” schedules. Reproductive opportunists include Australian desert species (e.g., zebra finches) and a few temperate zone species (e.g., crossbills). Opportunism has been assumed to be the consequence of selection favoring an ability to exploit favorable conditions that are rare and unpredictable. Our studies of one opportunist, the red crossbill, suggest an alternative: Species that are good at locating favorable conditions, unpredictable though they may be, may breed opportunistically not because they must, but because they can. This alternative hypothesis makes predictions different from those based on the conventional view, particularly regarding life history and endocrine mechanisms. Specifically, “cream skimmers” that breed flexibly because they are good at locating resource booms may invest in survival at the expense of current reproduction when they need to, and turn off the reproductive neuroendocrine system completely at times. In contrast, taxa making the “best of a bad situation” should invest in reproduction at the expense of survival when a reproductive opportunity arises, and maintain tonic readiness to initiate breeding rapidly at any time. We suggest that although some opportunists, including some populations of zebra finches, may match the conventional “best of a bad situation” scenario, others, including crossbills, may be “cream skimmers.”