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. [Illustration: PLATE 5 _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.] [Illustration: PLATE 6 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.