Effects of prior residence and age on breeding performance in yellow warblers

Age-related increases in reproductive success could be the result of better survival by successful breeders (survival hypothesis), greater dispersal b y unsuccessful breeders (dispersal hypothesis), and/or age-related differen ces in the ability to compete for breeding opportunities (constraint hypoth esis). We used banding and nesting data from four consecutive breeding seas ons to examine the effects of prior residency on several indices of breedin g performance in Yellow Warblers (Dendroica petechia). We compared the bree ding performance of returning birds with that of new arrivals, and of indiv iduals between successive breeding seasons. There were no differences in cl utch size between new arrivals and returning individuals, nor within indivi duals between successive breeding seasons. Among males, prior residence had no effect on whether a clutch was started, but among females the number of prior residents that initiated a clutch was higher than expected, and the number of new arrivals that did not was lower than expected. In contrast, t here were no differences in laying or hatching date between new arrivals an d returning individuals, but within-individual comparisons showed that malt s bred earlier in successive breeding seasons. Previous reproduction increa sed subsequent return rates only 1 out of 3 years in both sexes. Returning males were larger than new arrivals, but there were no differences in femal es. Within-individual size increases between successive breeding seasons oc curred in both sexes. These results are consistent with the constraint hypo thesis, but the proximate mechanisms by which these differences arise remai n to be determined.