Notes on the Nesting Habits of the American Robin (Turdus migratorius L.)

Abstract

The vast area occupied by the Robin during the breeding season indicates its toleration of a wide variety of habitats. In the norther portion of its range it pushes out beyond the limit of trees where it nests in low bushes. The factors limiting the northward distribution are not clearly evident. Vegetation is important, certainly as nesting cover and perhaps as food. Along the southern limit of the breeding range the species is extending its range. In certain parts of Texas and California the Robin has moved into new areas following the establishment of a water supply by man. In the southeastern states the species is pushing steadily nearer to the Gulf of Mexico and the Atlantic Ocean, having recently reached these bodies of water in certain regions. No change in the environment seems to have preceded or accompanied this extension in the latter region. In areas where the Robin is a common nesting bird it inhabits many diverse types of environment. The changes which man introduces seem usually to favor it. Dense forests are not unsuitable to this bird, nor are Robins absent from the treeless plains of the prairie states, but in both of these environments inhabited areas are more frequently selected than unpopulated ones. It is in the suburban areas that the requirements of the Robin are best filled. Open lawns are very productive feeding grounds and the shade trees growing about houses and along streets are used successfully as nesting sites. The fact that this bird thrives in and about villages and towns is responsible for its great increase in numbers during the period that man has settled throughout its range. The habitat must furnish sufficient food for the adults and their young. Many foods are eaten by Robins, but they must be relatively soft. Grains and other hard fruits cannot be digested. The habitat must provide water for in arid regions Robins occur only about sources of water. The cover requirements