Meeting Abstract

P2.16  Sunday, Jan. 5 15:30  Obligation versus exploitation: Does mobility affect the evolution of opportunistic breeding in songbirds? CORNELIUS, JM*; DINGLE, RDH; WATTS, HE; HAHN, TP; CSU-Monterey Bay cornelius@ucdavis.edu

Birds coordinate life cycle events with changing environmental conditions. For many this leads to seasonal partitioning of reproduction and survival-enhancing processes- such as plumage molt. In a few cases, however, unpredictable conditions favor opportunistic schedules. Opportunism results from selection favoring an ability to exploit rare and unpredictable resources and, because such opportunities may be limited, opportunism is traditionally assumed to be obligate (i.e., obligate opportunism). Obligate opportunists should invest in reproduction at the expense of survival when a reproductive opportunity arises and maintain readiness to initiate breeding at any time. We suggest an alternative: Species with high mobility may be good at locating unpredictable resources and may therefore breed opportunistically not because they must but because they can (i.e., rich patch exploitation). The two hypotheses make different predictions concerning life history trade-offs. Rich patch exploiters should be more likely to invest in survival-enhancing processes (molt, immune function, stress responsiveness) at the expense of current reproduction. We present data indicating that some opportunists may match the conventional “obligate opportunist” scenario while others may be better categorized as “rich patch exploiters.”