NESTING SUCCESS, NEST SITES, AND PARENTAL CARE OF THE LEAST FLYCATCHER IN DECLINING MAPLE FORESTS

We compared nesting success, nest site characteristics, and parental c are of the least flycatcher (Empidonax minimus) between healthy and de clining sugar maple (Acer saccharum) stands in southern Quebec, from 1 987 to 1989. On average, decline had caused a 20-30% foliage loss. A p revious study showed that the least flycatcher was the most abundant s pecies in these stands, even though some negative correlations between population densities and the intensity of decline were detected. Nest ing success averaged 53% and did not differ between healthy and declin ing sites. Nests were located in larger trees in declining sites, and foliage loss in the canopy above the nest was twice as high as in heal thy sites. Nestling feeding frequency was significantly higher in decl ining sites than in healthy ones. Mean meal size did not differ betwee n sites, suggesting that nestlings received more food in affected stan ds in spite of evidence of lower insect abundance. The nestling diet w as principally composed of Lepidoptera, Diptera, Hymenoptera, and Cole optera in declining and healthy sites. Parents spent more time at the nest in declining sites in 1988, presumably because of increased brood ing demand resulting from cold weather that year. We suggest that nest lings were thermally stressed in declining sites because of canopy fol iage loss and that parents had to work more (i.e., provide more feedin g and brooding) to maintain breeding success. Therefore, even though a moderate level of decline does not affect nesting success, flycatcher s may still be negatively affected in more subtle ways.