I found no nests of either species before they contained a complete complement of eggs and therefore was unable to ascertain the incubation period for these species. Brood patches were evident on female Sharp-tailed Sparrows by June 1, probably indicating that laying began near this date. Cruickshank (1942:456) lists egg dates of the Sharp-tailed Sparrow as concentrated in early June, with extremes of May 19 and August 4. He thinks the species probably has two broods. For the Seaside Sparrow, Cruickshank (1942:458) states there is probably but one brood and that egg dates are concentrated in early June, with extremes May 23 and July 2. Stone (1937:907, 911) considers four eggs a normal clutch for both species, but cites instances where three and five eggs were thought to be complete sets. Four of the eight Seaside Sparrow nests I found contained at least three eggs, and four contained at least four eggs. Four of the five Sharp-tailed Sparrow nests I found contained at least three eggs and one contained four eggs.
Female Seaside Sparrows do all of the incubation. The male, while the female is on the nest, remains a short distance away. He sings often and gives alarm notes when there is a local disturbance. These chipping notes bring the female off the nest, and then they both chip at the intruder. The male accompanies the female to the feeding grounds and normally they return together.
As previously mentioned, male Sharp-tailed Sparrows take no part in the nesting activities.
YOUNG
I studied growth and changes in behavior of the young. Since I could see no behavioral differences between the nestlings of the two species, this subject will be discussed jointly for the two forms.
Growth
The color of the natal downs of both species is similar. Dwight (1900:190), who saw newly hatched nestlings only of the Sharp-tailed Sparrow, described the color as grayish wood-brown. A series of white neossoptiles is present at the posterior end of the ventral tract in both species. These feathers are more numerous in the Seaside Sparrow. Dwight (1900:98) saw no neossoptiles on the underparts of any of the passerines he examined. Seaside Sparrows have a mid-dorsal row of downs in the dorsal tract near the uropygium. These feathers are lacking in the Sharp-tailed Sparrow and constitute the major difference, in this plumage, between the two species. The neossoptiles of three Seaside Sparrows and one Sharp-tailed Sparrow were counted. These counts were checked on the young birds studied in the field. The number and placement of these feathers appear in plate five. There appears to be a consistently greater number of natal downs in Seaside Sparrows, when compared with Sharp-tailed Sparrows.
Table 1—Daily Weight in Grams of Nestling Seaside Sparrows and Sharp-tailed Sparrows from Lavallette, Ocean Co., New Jersey.