Declines in animal populations worldwide are of critical conservation concern. However, without an understanding of optimal habitat preference, it is often difficult to determine what factors are driving these losses. Red-headed woodpecker (Melanerpes erythrocephalus L.) populations have declined by over 70% in the last 50 years, and yet in some areas the birds seem to maintain stable populations. The aim of this study was to empirically test the effects of various habitat factors on red-headed woodpecker abundance. We were particularly interested in whether oak species (Quercus sp.) present in largely savanna environments (an endangered ecosystem in the Midwestern United States) affect woodpecker abundance, as this has not been tested to our knowledge, and acorns of oaks are a critical food source for this bird. After conducting 138 point-count surveys and habitat analysis at sites throughout Northeastern Illinois, multiple linear regression with backwards elimination was used to generate a model showing which habitat factors most influenced red-headed woodpecker population density.
Results/Conclusions
Our model indicated that number of snags, percent white oak group trees, and percent oaks overall were not significant factors in predicting red-headed woodpecker abundance, however decreasing canopy cover, increasing dead limbs, and increasing red oak group trees at a site were significant factors. These results confirm and expand upon previous studies, suggesting that the oak savanna environment is important to the success of red-headed woodpecker populations. Our findings that percent red oak (primarily black oak Q. velutina) group trees, but not white oak group trees, is positively related to woodpecker abundance at a site deserves further attention, as this may indicate that the optimal habitat requirements of red-headed woodpecker populations are more specific than previously thought. Overall, knowledge of these factors is important for informing managers in conservation planning for this iconic species in the future.