A Nesting Study of the Wood Thrush

Publication Type:Journal Article
Year of Publication:1943
Authors:Brackbill, H
Journal:The Wilson Bulletin
Volume:55
Issue:2
Date Published:1943
ISBN Number:00435643
Keywords:Catharus, Catharus mustelinus, Corvidae, Cyanocitta, Cyanocitta cristata, Garrulus, Garrulus glandarius, Hylocichla, Hylocichla mustelina
Abstract:A pair of color-banded Wood Thrushes in suburban Baltimore remained together through two broods of three young each; nesting success was 100 per cent. The second nest was built 90 yards north-northeast of the first; the general locations of the two were similar; the placements differed. The immediate proximity of a stream was not found, as by some other observers, to be a habitat requirement. The female alone incubated. Attentive periods at the first and second nests averaged 31 and 27 minutes, respectively; inattentive periods 8½ and 6 1/10 minutes; the percentage of daylight hours spent on the nest was 78 and 80.3. The incubating bird's behavior during rain and during high wind is described. The first-brood hatch extended over two days, that of the second brood over three. The hatching hour of one egg was 6:59 A.M., 2 hours 17 minutes after sunrise. The shell was carried away. The female alone brooded the nestlings. Brooding lasted throughout the young's nest life. No progressive daily decrease in the brooding was found, nor any clear correlation between weather and amount of brooding except at temperatures of 93° F. and above, when attentiveness changed from covering to mere attendance--without shading. Both parents fed the young. The male made many more feedings than the female, but the female showed the better appreciation of the nestlings' needs; on the young's first days she gave them softer food than did the male, and she also trimmed certain portions away from some of the food he tendered. During comparable series of observations the average rate of feedings at the first nest was 9.3 per hour, at the second nest only 4.7, with equivalent food loads. Both parents were somewhat less attentive to the second brood than to the first. For example, the male guarded the first nest between almost all of the female's sittings, but guarded the second during only 60 per cent of her absences. At the first nest single periods of brooding by the female often encompassed two or three food trips by the male, but the female almost always flew away from the second nest the moment her mate arrived. The parents were equally responsible for the 50 per cent drop in feeding rate from brood to brood. The nestlings' excreta were usually eaten, by both parents, but two or three times, during morning twilight, were carried away. All of the first brood left the nest on the same day, when 12 and 13 days old. These birds were doing some of their own foraging by the age of 20 and 23 days; they continued to be fed by the parents to the age of 25 to 32 days; they left the territory, presumably independent, at 28 to 32 days. Two broods seem to be the rule at Baltimore. First-brood territory was about 100 × 100 yards in extent, second-brood territory probably 100 × 125 yards. Both adults defended territory against their own species, but not especially vigorously; the observed defenses are described. On the other hand, the female once fed a juvenile of a trespassing family that remained in the territory five days. The study pair were very tolerant of several other species, displaying hostility only toward a Blue Jay and a Purple Grackle. The notes uttered by male, female, and young are described, with comment on their uses; the female's use of a note suggesting song is mentioned. Partial albinism in the female was not inherited in the juvenal plumage by any of the six young.
URL:http://www.jstor.org/stable/4157231
Short Title:The Wilson Bulletin
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