Part 6

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.

======+================================================================+ Day | Ammospiza maritima | Average | ------+---------+------+---------+------+------+------+------+---------+ 0 | ... | 2.2 | 2.3 | ... | ... | 2.2 | 1.8 | 2.1 | 1 | 3.0 | 3.3 | 3.5 | 3.7 | 3.3 | 2.6 | 2.1 | 3.1 | 2 | 4.6 | 5.0 | 5.2 | 5.0 | 4.8 | 3.7 | 3.0 | 4.5 | 3 | 7.0 | 5.5 | 7.2 | 6.9 | 6.9 | 5.9 | 4.7 | 6.3 | 4 | 9.4 | 8.1 | 10.6 | 9.1 | 9.1 | 7.6 | 6.4 | 8.6 | 5 | 12.5 | 11.1 | 12.3 | 11.4 | 11.1 | 9.9 | 8.7 | 11.0 | 6 | 14.6 | 13.1 | 11.1 | 13.9 | 13.7 | 12.6 | 9.6 | 13.0 | 7 | 11.6 | 13.9 | 12.1 | 15.1 | 14.8 | 14.3 | 11.8 | 13.7 | 8 | 14.9 | 15.5 | 13.4 | 14.9 | 14.8 | 14.6 | 12.4 | 14.4 | 9 | 15.2 | 15.8 | 13.8 | 16.2 | 16.1 | 16.0 | 14.4 | 15.4 | 10 | ... | ... | ... | ... | 15.9 | 15.5 | 14.3 | 15.2 | ------+---------+------+---------+------+------+------+------+---------+

------+---------+------+---------+------+------+---------+ Day | Ammospiza caudacuta | Average | ------+---------+------+---------+------+------+---------+ 0 | 1.6 | ... | 1.8 | 1.7 | 1.7 | 1.7 | 1 | 1.8 | 2.3 | 2.5 | 3.0 | 2.1 | 2.3 | 2 | 3.3 | 2.7 | 4.1 | 4.6 | 3.1 | 3.6 | 3 | 5.0 | 3.7 | 5.9 | 6.4 | 4.7 | 5.1 | 4 | 6.8 | 5.4 | 8.4 | 9.1 | 6.7 | 7.3 | 5 | 8.6 | 6.9 | 10.7 | 11.2 | 9.5 | 9.4 | 6 | 10.2 | 8.9 | 12.8 | 13.0 | 10.9 | 11.2 | 7 | 12.1 | 11.4 | 14.5 | 13.6 | 12.3 | 12.8 | 8 | 13.5 | 12.9 | 15.3 | 14.5 | 13.3 | 13.9 | 9 | 12.2 | 13.4 | 15.9 | 14.9 | 13.6 | 14.0 | 10 | 12.7 | 14.0 | 15.5 | 15.0 | 14.0 | 14.2 | 11 | ... | ... | ... | 15.1 | 14.4 | ... | ------+---------+------+---------+------+------+---------+

These weights are not figured in the averages; see text.

Seven nestling Seaside Sparrows and five nestling Sharp-tailed Sparrows were weighed at 24-hour intervals until they left their nests. The birds were weighed in early morning before they had received much food. Weights of these individuals, and daily averages for each species are shown in Table 1. The weights in the zero column were of nestlings that had not been fed. The weight of one hatchling (1.9 gm.), which does not appear in the table, is included in the average for the zero column. Two young Seaside Sparrows, approximately a week old, fell out of a nest between 9:30 a.m. July 6 and 5:30 a.m. July 7. When I found them below the nest, at the latter time, their temperatures were far below normal, and they had lost a considerable amount of weight. These abnormally low weights were not figured in the averages. The weights of Sharp-tailed Sparrows 11 days old were obtained by confining the birds to the vicinity of the nest with a screen.

At hatching and throughout nestling life and post nestling life Seaside Sparrows average heavier than Sharp-tailed Sparrows of comparable age (Table 1). Weights of adults of the two species that were netted or collected between May 6 and June 27, 1955, within two miles of Chadwick, Ocean County, New Jersey, follow: Fourteen males of Ammospiza maritima averaged 24.2 gm. (21.9-27.4 gm.); three females averaged 22.3 gm. (19.8-24.4 gm.). Thirty-three males of A. caudacuta averaged 20.7 gm. (18.0-23.1, 25.8 gm.); 14 females averaged 17.8 gm. (15.3-19.0 gm.), 2.9 gm. less than the males. One female Sharp-tailed Sparrow, weighing 23.1 gm., was not included in the averages because it had an egg with shell in the oviduct.

Montagna (1940:195-196) weighed a series of breeding Sharp-tailed Sparrows (21 males; 5 females) from Popham Beach, Maine, and found the males to be only 0.2 gm. heavier than the females, but he stated that the small number of females weighed, and the high percentage of these that contained eggs, probably lessened the difference in weight found at other seasons.

The four linear measurements that I took on the same series of adults confirmed the size difference: Seaside Sparrows average larger than Sharp-tailed Sparrows, and males average larger than females in both species. The average and range for each measurement taken on the sparrows is presented in Table 2.

Four linear measurements were also taken daily on the young sparrows. A summary of these data appears in Figure 1.

Behavior

The first indication of hatching is a crack in the side of the egg along the line of greatest circumference. The crack is extended along this line by the egg tooth, and then contraction of muscles of the neck by the embryo separates the shell into two pieces. Extension of the legs frees the bird from the shell. I held the eggs of two Seaside Sparrows in my hand and watched this procedure. In each instance the young bird defecated in the shell before freeing itself. A barely audible "peep" note was heard from one hatchling Sharp-tailed Sparrow when I held it near my ear. When free from the shell, the young birds rest on their tarsi, abdomen and forehead; their down dries in a few minutes, and their skin becomes noticeably darker. One sparrow gaped five minutes after hatching and all the young gaped later the same day. The abdomen of the young becomes distended when they are fed by the parents.

Ammospiza caudacuta

Ammospiza maritima

Drawings of the nestlings of the two species of Ammospiza approximately three days of age showing the variation in the amount and placement of the neossoptiles in the two species. Abbreviations for feather tracts in which downs were found: ca, capital; h, humeral; a, alar; d, d´, dorsal; cr, crural; v, ventral.]

An aerial view of the marshes at Chadwick (upper left) and Lavallette (lower left). The Atlantic Ocean appears in the upper right of this photograph.]

TABLE 2--LINEAR MEASUREMENTS IN MILLIMETERS OF ADULT SEASIDE SPARROWS AND SHARP-TAILED SPARROWS CAPTURED OR COLLECTED WITHIN TWO MILES OF CHADWICK, OCEAN COUNTY, NEW JERSEY, BETWEEN MAY 6 AND JUNE 27, 1955.

========================================================= Ammospiza maritima --------------+-------------------+---------------------+ | 14 males | 3 females | --------------+-------------------+---------------------+ wing (chord) | 64.14 (60-66) | 58.33 (58-59) | tail | 55.28 (54-59) | 51.00 (49-53) | tarsus | 23.00 (22-25) | 22.17 (21-23) | culmen | 15.18 (15-15.5) | 14.50 (13.5-15.0) | --------------------------------------------------------- Ammospiza caudacuta --------------+-------------------+---------------------+ | 33 males | 15 females | --------------+-------------------+---------------------+ wing (chord) | 58.79 (55-61) | 55.67 (54-58) | tail | 49.48 (46-53) | 46.93 (45-50) | tarsus | 20.91 (20-22) | 20.30 (20-21) | culmen | 13.67 (13-14) | 13.23 (12.5-14.0) | --------------+-------------------+---------------------+

In the first 24-hour period after hatching the soft "peep" note is heard frequently. The young are better able to right themselves, and many feather papillae show distinctly through the skin.

On the second day young are capable of moving short distances by using their wings and feet. A thick ridge of tissue forms over the eyeball where the eyelids later delaminate. The call is now a double version of the "peep" note described above.

When the young are three days old the eyelids open, but only slightly. In the next three days the young become better co-ordinated and the eyes open fully. The egg tooth was last seen on a young bird on the sixth day. All incoming feathers remain sheathed until the seventh day.

On the seventh day young show the first signs of cowering. Previously, they all begged when I came to the nest. The remiges remain sheathed, but the body feathers emerge from the tips of the sheaths. A quiet reedy call replaces the "peep" note. A quiet, but squealing distress call was also first noted on the seventh day, when the young were handled.