HABITAT SELECTION AND BREEDING STATUS OF SWAINSONS WARBLERS IN SOUTHERN MISSOURI

Habitat selection and productivity are poorly documented for the Swain son's warbler (Limnothlypis swainsonii) throughout its breeding range. In southern Missouri in 1992-93, we quantified and compared habitat s tructure of occupied and unoccupied canebrakes (Arundinaria gigantea) and monitored nests to determine productivity. Twenty-nine of 100 cane brakes searched in 1992 were occupied by Swainson's warblers. Occupied canebrakes (n = 29) had higher cane density (P = 0.009), lower canopy (P = 0.018) and sub-canopy height (P = 0.008), and less herbaceous gr ound cover (P = 0.003) than did unoccupied canebrakes (n = 30). In 199 3, we compared 16 additional occupied sites with 15 new unoccupied sit es. Cane height (P = 0.030), tree diameter at breast height (dbh) (P = 0.006), and percent herbaceous cover (P = 0.001) were higher in occup ied than in unoccupied canebrakes, whereas percent leaf litter was low er (P = 0.011). Using the 1992 data, we developed a linear logistic re gression model to predict the probability of Swainson's warbler occurr ence. Applied to the 1993 data, this model correctly predicted only 3 of 16 occupied and 8 of 15 unoccupied canebrakes. We then pooled the d ata and developed a new model that correctly predicted 31 of 45 occupi ed and 35 of 45 unoccupied canebrakes. Clutch size averaged 3.55 eggs/ nest (n = 17) and nest production was 2.12 fledglings/nest. We failed to identify consistent distinctions between occupied and unoccupied ca nebrakes, and reproductive success was within the range reported for t his and similar species. Therefore, based upon our results, we found n o evidence that suitable habitat limited Swainson's warbler abundance in Missouri.