Tree Species Preferences of Foraging Songbirds During Spring Migration in Floodplain Forests of the Upper Mississippi River: Tree Data

We evaluated bird foraging preferences for tree species during spring migration 2010-2013. We used the point center-quarter method to assess relative availability (tree importance values, IV) of tree species and tallied bird foraging observations on tree species as well as recording the phenophase of used trees on five 40 ha plots of contiguous floodplain forest between La Crosse, Wisconsin, and New Albin, Iowa, from 15 April through 1 June 2010-2013. We quantified bird preferences by comparing proportional use of tree species by each bird species to estimates of tree species availability (IV) for all four years and for each year separately. Bird data records contain the plot identity, date, time of the observation, species of bird, sex if distinguishable, tree species in which it was foraging, location the bird was in the tree, dbh of the tree, phonological phase of the tree and any comments about the observation (foraging in flowers, if tree was in flower, etc.)