Artificial cavities enhance breeding bird densities in managed cottonwood forests

The paucity of natural cavities within short-rotation hardwood agroforests restricts occupancy by cavity-nesting birds. However, providing 1.6 artificial nesting cavities (nest boxes)/ha within 3- to 10-year-old managed cottonwood forests in the Mississippi Alluvial Valley increased territory density of cavity-nesting birds. Differences in territory densities between forests with and without nest boxes increased as stands aged. Seven bird species initiated 38 nests in 173 boxes during 1997 and 39 nests in 172 boxes during 1998. Prothonotary warblers (Protonotaria citrea) and eastern bluebirds (Sialia sialis) accounted for 67% of nests; nearly all warbler nests were in 1.8-L, plastic-coated cardboard (paper) boxes, whereas bluebird nests were divided between paper boxes and 3.5-L wooden boxes. Larger-volume (16.5-L) wooden nest boxes were used by eastern screech owls (Otus asio) and great crested flycatchers (Myiarchus crinitus), but this box type often was usurped by honey bees (Apis mellifera). To enhance territory densities of cavity-nesting birds in cottonwood agroforests, we recommend placement of plastic-coated paper nest boxes, at a density of 0.5/ha, after trees are >4 years old but at least 2 years before anticipated timber harvest.