Part 7

On the eighth day the remigial sheaths become gray (previously they were dark blue) and begin to slough off. When removed from the nest, the young attempt to escape. Begging is less frequent and cowering is the predominant attitude towards intruders.

The first young of both species left the nest on the ninth day. It must be remembered, however, that this remark, and succeeding remarks, concerning departure of young from nests pertains to young that were disturbed daily by me. The others climbed to the edge of the nest when they were left alone, but remained in the nest when they were all replaced. Gaping was recorded once on the ninth day. Stuart W. John watched two Sharp-tailed Sparrows on my study area leave a nest. They climbed out and immediately hid in a tussock of grass a few inches behind the nest.

On the tenth day when I parted the branches over one Seaside Sparrow nest, the four young jumped from the nest and scattered in the grass. One of these birds gave a chipping note similar to the distress call of adults. No bird remained in a nest longer than ten days. Four young left the nest after nine days, seven young left on the tenth day. When the young leave the nest they are able to run rapidly through the dense grass. The young are fed by the parents for approximately 20 days after they leave the nest. Twenty-three days after one young Seaside Sparrow left the nest it was netted at the opposite end of the island, 300 yards from the territory of its parents.

Young Seaside Sparrows fly in an uncertain but characteristic manner when they are flushed from the grass. They dive clumsily into the grass after a short flight, making it easy to identify them as birds of the year.

The plumage of sparrows of the Genus Ammospiza serves to conceal them in their habitat. In juvenal and adult plumage, the Sharp-tailed Sparrow is a brown-backed, streaked bird, the color and pattern blending with the matted grasses (Allen, 1925:67) where the species feeds and nests. The Seaside Sparrow, as an adult, is olive-gray. Its color corresponds to that of the substratum where the species forages. The juvenal plumage of the Seaside Sparrow resembles that of the Sharp-tailed Sparrow. I believe that young Seaside Sparrows have this brown, streaked plumage because they spend most of their time in the dense grass. In the Seaside Sparrow a complete post-juvenal molt begins in late August. The resulting plumage resembles that which is acquired by the adults when they complete their post-nuptial molt (Dwight, 1900:192-193).

FOOD, FEEDING, AND CARE OF THE YOUNG

The food habits of Seaside Sparrows and Sharp-tailed Sparrows have been studied by Judd (1901:64-66), who concluded that both species are highly insectivorous. In 51 stomachs of Sharp-tailed Sparrows 81 per cent of the contents was animal. The results of investigation of stomachs of Seaside Sparrows were similar. In each of the two species the bill is more elongated and less conical than in other sparrows. For the two species studied, the shape of the bill seems to be an adaptation for feeding on insects.

When searching for food, Sharp-tailed Sparrows walk through the dense black grass, deftly brushing stems aside with their bill as they go. Open areas are generally traversed by rapid running. I never noticed either species hopping. They stop to investigate openings in the matted understory of grass, often sticking their heads into the holes. Many times I saw these sparrows stretch or jump to pick insects from stems. Many droppings, almost certainly those of Sharp-tailed Sparrows, were present in areas of damp, matted grass. Females, when feeding young, obtain most of the food near the nest; several times I saw birds catch insects when they were within inches of their nest. Sharp-tailed Sparrows feed also along the banks of pools and creeks, and along the perimeters of marshes. Sharp-tailed Sparrows seem to be less restricted in the types of feeding habitats they can use than are Seaside Sparrows.

Seaside Sparrows always returned to the edge of the marsh to procure food, according to my observations. The birds at Lavallette fed extensively on noctuid moths. In the feeding territories of two pairs of Seaside Sparrows, along the strip of washed-up eel grass, I found at least 40 wings of these moths. In several instances the four wings of one moth were lying close together in the same relative position in which they had been on the animal. Legs and pieces of thorax were also discarded occasionally. I watched adults take these moths from the stems of the smooth cord-grass and snip the wings off with their bills. Moth wings were present in the other feeding territories, but not in so great a quantity. Once I saw a female return to the nest with a spider in her bill. Spiders were abundant throughout the marsh.

Dwight (1900:193) was surprised that the two species living in the same environment, and therefore suffering equally from abrasion from the coarse marsh grasses, should have a different number of molts per year. The Sharp-tailed Sparrow has a complete pre-nuptial, as well as a complete postnuptial, molt. The Seaside Sparrow has only a postnuptial molt, the nuptial plumage being acquired by wear. My observations of the feeding habits of the two species indicate that they do not live in precisely the same environment. The Sharp-tailed Sparrow, which has two complete molts annually, generally forages in dense, abrasive vegetation. The Seaside Sparrow, which has but one molt each year, forages in relatively open areas.

Several times I saw adult Seaside Sparrows fly from their nests toward the feeding territories with fecal sacs in their bills. On the feeding grounds, I found several of these sacs discarded near the moth wings. I saw also female Sharp-tailed Sparrows leave their nests with fecal sacs. I did not see sparrows of either species swallow fecal sacs.

One nest, that of a Seaside Sparrow containing four young, became fouled with excrement when the young were nine to ten days old. It is interesting that these young were cared for only by a male, at least for the last four days of nest life, and that one of the young birds died two days before the others left the nest. This male's mate was probably a female that I banded on June 18 (the young left the nest on June 23) and never saw again. A female, whose mate was probably killed by me on June 15, continued to incubate the three eggs until they hatched on June 29, but deserted the nest when the young were two days old. This female was seen again on August 1 more than 500 yards from her nest site on the island immediately north of the study area.

Devotion of parent passerine birds to the young typically increases with the growth of the young (Nice, 1943:245). This may explain why the mateless female deserted its nest when the young were only two days old, whereas a mateless male continued to care for his six-day-old young. The death of one nestling, and the eventual fouling of his nest may indicate that the job was too much for one adult to perform. The correlation of increasing devotion of the parents with increasing age of the young was further illustrated by the distraction display, noted by me, on the part of a pair of Seaside Sparrows on the day their young left the nest. As I lifted the four nine-day-old young from the nest for weighing, they began to give the distress call. This attracted the parents from the feeding area approximately 60 yards away. The two adults ran around on the ground within ten feet of me giving the tsip note and fluttering their wings. Several times the adults flew within a few feet of me, making a vibrating sound with their wings. Although I realized the function of this display, it was distracting nevertheless.

ACKNOWLEDGMENTS

I am indebted to Assistant Professor Harrison B. Tordoff for comments and suggestions throughout the preparation of this manuscript, and to Mr. Stuart W. John who photographed the birds and the habitat scenes. The aerial photograph of the study island is reproduced with the permission of Fairchild Aerial Surveys, Inc., and the photograph of Lavallette and Chadwick through the kindness of the Lavallette Yacht Club. The drawings were made by Mr. John R. Beeder. Additionally I wish to express my gratitude to Dr. Dean Amadon, Mr. H. Lyman Sindle, and Mr. Lester B. Woolfenden for help and advice in certain aspects of the field work.

SUMMARY

A comparative study of the breeding behavior of the Seaside Sparrow and Sharp-tailed Sparrow was made in New Jersey in 1955.

Observations of marked individuals indicate that the Seaside Sparrow is monogamous and territorial, whereas the Sharp-tailed Sparrow is promiscuous, and at least the male is non-territorial. The male Seaside Sparrow defends its territory by chasing and singing. The male Sharp-tailed Sparrow confines itself to a breeding home range. This range is not a territory; it is inhabited by several males. Female Sharp-tailed Sparrows may be territorial; this is not certainly known.

The Seaside Sparrow sings louder, more distinctly, more often, and from more exposed perches than does the Sharp-tailed Sparrow. These characteristics seem to be correlated with territorial habits. Other calls are described and their functions are discussed.

The Seaside Sparrow nests in marsh-elder bushes, or in areas of mixed vegetation. The Sharp-tailed Sparrow prefers the inner, drier areas of a marsh, where black grass is dominant. The Seaside Sparrow places its nest farther above the ground than does the Sharp-tailed Sparrow. Both species used only black grass in constructing the nest.

Copulation is described. The incubation period was not determined for either species. Three or four eggs seem to be a normal clutch. Females do all of the incubating.

The young remained in the nests nine to ten days. These nests, of course were disturbed, for I visited them at least daily. The nestlings of the Seaside Sparrow are fed by both parents. Male Sharp-tailed Sparrows seem not to know the location of the nests and take no part in rearing the young at least up to time of fledging. The natal down of both species is described. Data on growth and behavior of the young are presented.

Seaside Sparrows obtained most of their food from the shoreline of the marsh, in areas of open mud and smooth cord-grass. The plumage of the adult matches, in color, this mud. The Sharp-tailed Sparrow feeds everywhere in the marsh, but mostly in areas of dense and matted black grass. The plumage on the dorsum of this species is brown and streaked resembling the dead grass. Juvenal Seaside Sparrows, which spend most of their time concealed in the dense grass, resemble adult and juvenal Sharp-tailed Sparrows in plumage. Sharp-tailed Sparrows molt completely twice per year. The Seaside Sparrow molts but once per year. The difference in number of molts, too, is correlated with habitat preference, since the grassy forage habitat of the Sharp-tailed Sparrow must result in greater abrasion of the plumage than does the open feeding habitat of the Seaside Sparrow.

LITERATURE CITED

ALLEN, GLOVER M.

1925. Birds and their attributes. Marshall Jones Co., Boston, Massachusetts. xiii + 338 pp., frontispiece, 45 pls., 6 figs.

CRUICKSHANK, ALLAN D.

1942. Birds around New York City, where and when to find them. The American Museum of Natural History, Handbook Series, No. 13, New York. xvii + 489 pp., frontispiece, 35 pls.