Reproductive success is a misleading indicator of nest-site preferences inthe Red-winged Blackbird

Several methods are used to detect nest-site preferences of birds. One meth od postulates that individuals will prefer those nest-site features that in crease their reproductive success. To determine which features affect repro ductive success, and hence should be preferred, the method examines correla tions between reproductive success and various nest-site features. When a s tatistically significant correlation is found, it is concluded that individ uals exhibit a preference for that feature. In the absence of a correlation , it is concluded that individuals are indifferent to the feature. Here, I argue that this method may lead to misleading conclusions. If good sites ar e abundant, all individuals should choose them. Consequently, there will be little variation in the features of the chosen sites. This limited variati on, when related to reproductive success, may fail to yield a statistically significant correlation and thus lead to the erroneous conclusion that ind ividuals have no preference. An alternative method of detecting nest-site p references is to compare features of chosen sites with features of availabl e sites. In this study, I used both methods to investigate nest-site select ion in the Red-winged Blackbird (Agelaius phoeniceus). I compared vegetatio n features of nest sites with those of randomly selected sampling sites and found significant differences. The differences imply that Red-winged Black birds prefer vegetation that grows in small patches and is tall and sparse, and the plants have thick stems. I found no relationship between these veg etation features and reproductive success. These results suggest that Red-w inged Blackbirds have strong preferences for certain vegatation features, b ut these preferences cannot be detected from correlations with reproductive success.