Vesper sparrow

Locally, the vesper sparrow breeds in the inner coastal plan of South Jersey and the Piedmont, Highlands, and Ridge and Valley regions of northern and central New Jersey. Nesting is concentrated in the north-west of the state, throughout most of New Jersey.

Vesper sparrows are rare fall migrants in New Jersey, occurring from mid-October to mid-November, with an average of ten records each fall at Cape May Point. Vesper sparrows rarely over-winter along the southern coastal region of New Jersey. The vesper sparrow is an extremely rare spring migrant. Spring migrants occur from early April to mid-May.

Vesper sparrows reside in cultivated fields, grasslands, and pastures. Farmed areas that are adjacent to fallow fields or contain uncultivated strips along fence-rows are favored. These fallow areas provide nesting habitat, cover, foraging sites, and singing perches. On active farmlands, human disturbance and crop harvesting can threaten nesting sparrows. Fallow fields and grasslands provide a safer haven for nests.

Vesper sparrow habitats are typically sparsely vegetated with patches of bare ground, low vegetation and scattered shrubs. Habitats are typically dry and well drained. Nests are placed within clumps of cover that afford protection from predators. Elevated perches, such as fence posts provide singing posts from which males can advertise their territories and attract mates. Territory size may range from 1.2 to 7.9 acres. Similar habitats are used throughout the year.

The diet of the vesper sparrow consists of invertebrates and seeds. During the summer months, the diet consists largely of invertebrates such as beetles, grasshoppers and other insects. Weed and grass seeds are also consumed during this time, although in a smaller proportion. Young sparrows are fed invertebrates almost exclusively. Vesper sparrows are a beneficial species in agricultural areas, as they consume many crop-destroying insects. In the fall and winter, seeds of various plants are sought. Vesper sparrows forage on the ground in weedy fields, brushy edges, and recently mowed fields.

During April, male vesper sparrows arrive on their breeding grounds and establish territories. About a week later, the females return. Vesper sparrows exhibit site fidelity, as pairs return to the same nesting location during consecutive years. They often form small colonies, with three to six pairs nesting in an area.

Over a one- to two-week period, the female vesper sparrow constructs a cup nest of grasses, and lines it with thinner grasses. The ground nest often is concealed in a hollow at the base of a weed or grass tuft.

By the second or third week of May, the female lays a clutch of three to five greenish white eggs that are blotched with brown. Both parents, although primarily the female incubate the eggs for 11 to 13 days. The protective incubating adult will not flush from the nest until nearly stepped upon, at which time it will feign injury to lure an intruder away. At 9 to 13 days, the chicks, not yet independent, leave the nest. The adults continue to care for the young, which seek cover in the surrounding vegetation, for several weeks. If a pair produces a second clutch, the male will tend to the first brood while the female begins incubating the subsequent clutch.

Due to its dependence on farming fields, the vesper sparrow has suffered significant population declines resulting from the ebb of agriculture in New Jersey. The vesper sparrow has been adversely impacted by the conversion of farmlands to development. In addition, habitat loss has resulted in the fragmentation of agricultural areas. Habitat fragmentation may impede vesper sparrows from nesting, as they require large tracts of suitable habitat.

Within cultivated areas, vesper sparrows may be negatively affected by agricultural operations. Early or frequent harvesting may destroy nests and kill sparrow eggs or young. Likewise, the cultivation of fallow strips and edges surrounding farm fields eliminates habitat. A reduction in cover may make vesper sparrows and their young more vulnerable to predators. The vesper sparrow is also a common host for the brown-headed cowbird. This bird is a nest parasite that lays its eggs in the nests of other birds at the expense of the host bird.

Management for vesper sparrows must include the preservation of breeding habitats such as farmlands, grasslands, and open fields. Large, contiguous tracts of suitable habitat, should receive the highest conservation priority. Within cultivated areas, management practices can be implemented to benefit vesper sparrows. Mowing within nesting habitats should be restricted during the breeding season to protect nests and young. Fence rows and fallow strips of herbaceous or shrubby vegetation should be set aside as uncultivated land, yet should be maintained as early successional habitats, either through selective cutting or mowing.

In uncultivated lands such as fallow fields or grasslands, management practices must be implemented in order to maintain the successional stage. Controlled burns, selective cutting, mowing, or grazing can be implemented as habitat management tools. Management, which must be conducted outside of the breeding season, can be executed prior to the birds’ arrival. Fields should be managed on a rotational scheme, so that no more than half of the grassland area is burned or cut in one year. To enhance managed habitats for vesper sparrows, a mixture of native warm-season grasses should be planted.