Meeting Abstract

111.3  Saturday, Jan. 7  Carryover or compensation? The effect of delayed plumage molt in House Finches (Carpodacus mexicanus) BRAZEAL, KR*; HAHN, TP; UC Davis; UC Davis

Most animals need to time their annual cycle stages to appropriately correspond with optimal environmental conditions. In seasonally-breeding birds, the timing of the transition between breeding and molt represents an important life-history trade-off between the benefits of extended current reproduction and the costs of delayed molt, which can impair survival. Another consequence of delayed molt could be a carryover effect, causing delayed molt in subsequent years. Conversely, proximate mechanisms controlling molt may allow for animals to make appropriate timing adjustments. This study examined whether such a carryover effect exists. House finches captured in June 2010 were given either control or testosterone implants prior to the start of molt. The implants were replaced every 2 months and then removed in December. Testosterone treatment delayed the beginning of molt by 2-3 months in most birds and completely prevented molt until implant removal in a few birds. Despite the lengthy delay of molt in 2010, the timing of molt in 2011 did not significantly differ between the control and previously T-treated groups. Those birds that did not molt until after implant removal therefore completed two molt cycles within the same calendar year. Molt start date in 2010 and 2011 was significantly correlated among control birds but not among T-treated birds. These results suggest that the timing of molt can carryover from year to year on a small scale, but extremely late-molting birds are able to compensate in subsequent years and still regain a normal molt schedule.