Comparative Breeding Behavior of Ammospiza caudacuta and A. maritima Part 2

Both species emit alarm notes. Although variable, the Seaside Sparrow has two general types. One, recorded by me as a short _chip_ or _tick_ was given by both s.e.xes whenever I was near a nest. The other type, a high, sharp _tsip_, is indicative of a higher degree of excitement.

When I captured young already out of the nest, or when I investigated nests containing young old enough to depart, the adults gave this call.

The tail is jerked downward each time this note is given.

The alarm call of the Sharp-tailed Sparrow is not so loud as that of the Seaside Sparrow and it is not given so often. I described it as a short _tsick_ or _tsuck_. Females emitted such calls when I was at their nests or when male Sharp-tailed Sparrows came near their nests.

Males may have a similar call, but I never recorded it. Montagna (1942a:116) remarks on the quietness of this species. This is especially evident when one compares Sharp-tailed Sparrows with Seaside Sparrows.

PLATE 1

[Ill.u.s.tration: FIG. _a_. An aerial photograph of the Lavallette study island. One inch equals approximately 375 feet. The area covered by sand has been extended since this photograph was taken. This is indicated in figure _b_ of this plate.]

[Ill.u.s.tration: FIG. _b_. Map of the Lavallette study island. All fringillid nests that I found are indicated and the territorial boundaries of the Seaside Sparrows are shown.

[triangle]--Seaside Sparrow [dot]--Sharp-tailed Sparrow [star]--Song Sparrow]

PLATE 2

[Ill.u.s.tration: FIG. _a_. The south sh.o.r.e of the Lavallette study island showing the two major driftlines and the spa.r.s.ely vegetated areas. This is the feeding habitat of the Seaside Sparrow.]

[Ill.u.s.tration: FIG. _b_. A close-up view of a segment of the sh.o.r.eline.

Note the s.p.a.cing of the clumps of cord-gra.s.s (_Spartina alterniflora_).

A six inch ruler propped against a 12 inch stick is included to indicate the size and s.p.a.cing of the plants.]

PLATE 3

[Ill.u.s.tration: FIG. _a_. The inner portion of the marsh on the Lavallette study island showing the rows of marsh-elder bushes (_Iva frutescens_) and the extensive areas of black gra.s.s (_Juncus gerardi_).

Areas of mixed black gra.s.s and cord-gra.s.s appear in the foreground. All the nests of Sharp-tailed Sparrows were found in the areas of black gra.s.s. Four of the eight nests of Seaside Sparrows were in the marsh-elder. One of the blinds that I used is shown in this photograph.]

[Ill.u.s.tration: FIG. _b_. A mated, banded pair of Seaside Sparrows in a dead marsh-elder bush near their nest. Note the abdomen of a moth protruding from the bill of the female on the right.]

PLATE 4

[Ill.u.s.tration: FIG. _a_. A female Sharp-tailed Sparrow at the entrance to her nest. The throat on this bird is dark because of dye applied by me.]

[Ill.u.s.tration: FIG. _b_. The nest of a Sharp-tailed Sparrow viewed from above. Stems of black gra.s.s were parted to take the picture. The outer rim of this nest (lower right) is made of living stems of black gra.s.s.]

COPULATION

In late June at the Lavallette area there was an influx of unbanded Seaside Sparrows. Certain of these new arrivals established territories in areas unoccupied by the remaining original residents. These new residents were birds that probably had unsuccessful nestings elsewhere.

Because of tropical storms that almost covered the island with water in August, I doubt that any of these late nestings were successful. On July 7 at 8:30 a.m., while watching a pair of these new arrivals, I recorded my only observation of copulation in the Seaside Sparrow. The female seemed to be searching for a nest site when copulation occurred.

The female crawled about in a marsh-elder bush seemingly testing the various forks in the branches for size. The male followed her, remaining a few inches above and behind. Several times the two birds disappeared in the lower branches and were hidden by the surrounding black gra.s.s. Finally, while the female squatted on a branch the male mounted. He fluttered his wings before mounting and continued to do so as coition took place.

I began observations at Lavalette on June 16, too late to observe copulation of the early residents. All the nests contained eggs by that time. At Chadwick, pair formation seemingly never occurred, at least with the males I was studying. The territories established by males at Chadwick contained few marsh-elder bushes. Possibly females, finding no suitable nest sites, refused to accept these territories.

Copulation in the Sharp-tailed Sparrow was observed several times. It occurs most frequently in the course of, or immediately following, a fight between several males. I do not know what instigates the gathering of several males into these groups; it may be a certain behaviorism of a female, or possibly, merely the appearance of a female. Montagna (1942a:117) was convinced that females of _A. c.

subvirgata_ were present in these fights. On the other hand, in two instances with _A. c. diversa_ where he collected all the birds in the group, no females were present. Twice, at Chadwick, my observations indicated that females of _A. c. caudacuta_ were not always involved in these groups. In these instances all the birds in the group had previously been banded and diagnosed as males. Possibly a female was the original stimulus of these groups, and she may have disappeared while the males were fighting with each other. I found it difficult to distinguish fighting males from a copulating pair. On June 3, however, a banded pair was observed. Copulation occurred on the ground. The male fluttered his wings as he mounted and the female remained motionless.

Copulation lasted approximately three seconds; immediately thereafter the male flew to a nearby cattail stem and the female climbed a tussock of gra.s.s and chipped quietly. This same female was seen to copulate with other males, and males were observed copulating with several females.

_A. m. maritima_ is monogamous, the pair-bond being maintained throughout a breeding cycle. _A. c. caudacuta_ is promiscuous, relations between the s.e.xes being limited to copulation. For _A. c.

subvirgata_ a relations.h.i.+p other than promiscuity has been intimated (Lewis, 1920:587-589). Concerning observations of the nest he found at Yarmouth, Nova Scotia, Lewis wrote: "The nest was found after I had quietly watched the parent Sparrows for about an hour, while they were bringing food to their young.... The male sang from time to time from a piece of driftwood on the marsh about 30 feet distant from the nest.

When I was examining the nest and the young birds, the parents made no demonstration for some minutes, but later they came near and uttered chip's, much like those of Savannah Sparrows."

NESTS

I found the nests of all eight pairs of Seaside Sparrows which nested on the Lavallette study island in 1955. Four nests were supported by marsh-elder bushes, three of which were dead. These nests were placed low enough to be hidden by numerous stems of black gra.s.s, as were the other four nests. Of the remaining four nests, three were placed in tussocks of black gra.s.s and the fourth one gained support mostly from cord-gra.s.s stems. The eight nests ranged from 9 to 11 inches (9.6 inch average) from the rim to the ground, the four nests in the bushes being the highest. The outside diameters of the nests ranged from 3 to 4.5 inches (3.9 inch average) and the outside depth varied between 2 and 3.5 inches (2.7 inch average). Seven of the nests had an inside depth of 1.5 inches; the other one was only an inch from the rim to the floor. The inside diameter of the cup varied between 2 and 2.5 inches.

As mentioned above all eight nests were s.h.i.+elded by stems of black gra.s.s. Stems were not woven over the nests by the birds; rather it was the choice of the nest sites that resulted in the concealment. The only plant used for nest material was black gra.s.s.

In all cases the black gra.s.s limited the directions from which the nests could be entered. Six of the nests were approached from a direction varying between northeast and southeast. The prevailing winds of spring and summer are from the south and southwest; the black gra.s.s consequently leans in the opposite direction. The remaining two nests were entered from the northwest. These were nests built in marsh-elder bushes where the gra.s.s stems were held upright by the branches of the bushes.

One nest, built in a small dead marsh-elder bush, was tilted by the growth of stems of black gra.s.s which were used for support on one side.

This tilting did not cause the contents to spill, but, I judged, did cause the adults to desert the nest.

Seven nests of the Sharp-tailed Sparrow were found; two of these were old nests. Four of the five nests used in the breeding season of 1955 were found on the Lavallette marsh study area, the other one I discovered on the Chadwick marshes. Two young Sharp-tailed Sparrows that I saw at Lavallette were not from nests I found, nor were they from the same nest. Therefore, a minimum of six Sharp-tailed Sparrows bred on the Lavallette island. Measurements were taken of only the five nests that were used in 1955. The Sharp-tailed Sparrow builds its nest closer to the ground than does the Seaside Sparrow. The five nests were five to six inches off the ground; the two nests of a previous year appeared to have been no higher. The Sharp-tailed Sparrow nests were built in areas where black gra.s.s was the predominant plant, and the nests were constructed entirely from this gra.s.s. The outside diameters varied from 3 to 4.25 inches (3.4 inch average). The outside depth of the nests varied from 2 to 3.5 inches (2.8 inch average). The inside depth was 1.5 inches in all nests and the inside diameter ranged from 2 to 2.5 inches (2.1 inch average).

Harrison F. Lewis (1920:587) studied a nest of _A. c. subvirgata_ in a small salt marsh near Bunker's Island at the southern end of Yarmouth Harbor, Yarmouth, Nova Scotia, which he found on June 12, 1920. For details of this nest I quote Dr. Lewis. "The nest proper was a neat, round cup of fine, dry, dead gra.s.s, with some horsehair in the lining.

Its foundation consisted of some small ma.s.ses of 'eel-gra.s.s' and roots.

Its dimensions were: inside diameter, 2.5 in.; outside diameter, 4.5 in.; inside depth, 1.5 in.; outside depth 2.375 in. It was elevated above the general surface of the marsh by being placed on the top of a low, gra.s.sy ridge, about fourteen inches high, formed from material thrown up when a ditch was dug across the marsh, many years before.

During some storm a mat of dead 'eel-gra.s.s' had been left on top of this ridge, and this had later been lifted by the growing marsh gra.s.s, leaving several inches between it and the ground. The nest was placed on the northwest edge of this mat, about half of the nest being under it, while the other side was sheltered and concealed by gra.s.s about six inches high. The nest was not sunk in the ground at all."

Two of the nests found were entered from the north-northeast, the other three from the east-southeast. All five nests were sheltered above by stems of black gra.s.s. Three of the nests were beneath a layer of dead black gra.s.s where a clump of erect living stems parted the mat. One nest (pl. 4, fig. a) was situated where cattail stubs held the black gra.s.s somewhat erect. Green stalks as well as dead stalks were woven into a canopy over this nest. Another nest was constructed on a mat of black gra.s.s under and among numerous horizontal living stems, some of which were woven into the outer lining of the nest (pl. 4, fig. b).

Nests of both species were found in tussocks of black gra.s.s. The locations of these sites differed. The Sharp-tailed Sparrow prefers the higher and therefore dryer portions of the marsh where black gra.s.s is the characteristic plant. Contrastingly the Seaside Sparrow almost always chooses the wetter portions of the marsh (Cruickshank, 1942:45; Forbush and May, 1939:514; Stone, 1937:906; personal observations) where several species of plants are abundant. In areas that have been ditched, as have almost all marshes in New Jersey, the mound of excavated muck is ideal for the growth of marsh-elder. Rows of these bushes are present on many of the marshes of New Jersey (pl. 3, fig.

a). The location of four of the eight Seaside Sparrow nests in these "hedgerows" indicates that they provide suitable, if not preferred, sites for the species.

EGGS AND INCUBATION

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 pa.s.serines 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 const.i.tute 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.