Breeding Behavior and Nesting of the Eastern Robin

Abstract

The wide distribution, aibundance, comparative tameness and accessibility of the robin, Turdus migrattorius, has made it a popular subject for study. Famer (1945, 1949) has taken advantage of the large numbers banded to compute its mortality rates and longevity; Young (1951) has examined the territorial behavior, Speirs (1946) the movements, and there are innumerable short notes on various aspects of its life history. However, the only previous extensive study of the breeding behavior and nesting of the robin is that of Howell (1942). This paper furnishes data to supplement those of Howell's, discusses the subject of mating behavior, and considers in detail the breeding success, the nesting season, and population dynamics. The material was gathered during the spring and summer from 1947 to 1949 at Madison, Wisconsin. Two major study areas were used. The first, known as the Ho-Nee-Um area, is located in the University of Wisconsin Arboretum. It is a small (5.2 acres) park-like area, where arbor-vitae, Thuja occidentalis, furnished the main nesting cover. For a detailed description see Young (1949a, 1951). Many robins at Ho-Nee-Um were individually marked in connection with a concurrent territory study (Young 1951), and these marked birds were also watched for breeding behavior. Marked birds are herein referred to as M1, M12, etc. ( c ), and 9F, 13F, etc. ( V ). This study area was visited almost daily during the breeding season in each of the three years; the visits usually lasting from 2 to 3 hours,, with a total of about 700 hours spent on the area. The second area used was the Forest Hills Cemetery at Madison, which was under observation mainly during 1948 and 1949. It was, usually visited about 3 times a week, each visit lasting from 1 to 2 hours, for about 100 hours total. The nests were ordinarily examined every other day. On a few unavoidable occasions longer lapses of timne intervened, and at certain, stages the nests were checked more frequently. Each visit to a nest was of as, short a duration as possible (to determine the status) since intensive observation of incubation, brooding, and development of the young was not in the scope of the study.