Savannah sparrow

Savannah sparrows breed in the Ridge and Valley and Highlands regions of northern New Jersey and in the inner coastal plain of southwestern New Jersey.

The savannah sparrow is a common fall migrant in New Jersey, from mid-September through early November. Spring migrants occur from mid-March through late April. The savannah sparrow is an uncommon winter resident, found in small flocks along the coast, inland grasslands, and fields.

Savannah sparrows nest in a variety of open habitats. Suitable fields must provide a mix of short and tall grasses, a thick litter layer, dense ground vegetation, and scattered shrubs, saplings, or forbs. Savannah sparrows are relatively tolerant of vegetative succession, and occupy fields of varied ages, including those with early woody growth. In the nonbreeding season they inhabit a variety of habitats including coastal dunes, fallow fields and pastures.

Savannah sparrows rely on seasonally abundant food sources. They feed mainly on insects in the summer and grass and weed seeds during the winter. In the nesting season, they feed on invertebrates such as insects, larvae, and caterpillars. Young sparrows are fed invertebrates along with fruit and berries.

A few weeks after the males arrive, the females arrive and pairs are formed. Savannah sparrows require large grasslands of approximately 20-40 acres. Within this area males establish territories of 1-2 acres. In areas of high-quality habitat, they may nest semi-colonially, or polygyny may occur. Individuals often return to the same nesting site in successive years and mated pairs typically remain together in subsequent years.

The female constructs a cup nest, concealed by vegetation, in a slight depression on the ground. Located within clumps of grass or at the base of a shrub, the nest is woven of thick grasses and lined with thinner grasses.

Egg dates for the savannah span from mid-May to late June. The female lays a clutch of four to five eggs. Eggs are pale and heavily marked with reddish brown mottling. The female incubates the eggs for 8 to 13 days. Both adults feed and guard the young, performing distraction displays to lure predators away from the nest. Monogamous males provide a greater amount of parental care than polygynous males. At 8 to 14 days, the young leave the nest but remain with their parents for an additional two weeks. By about 20 days old, the young are able to fly.

In some cases the pair may produce a second clutch. This extends the breeding season into late July or early August. If only one clutch is produced, the adults spend a longer amount of time with their fledglings, remaining with them for an additional three weeks or more. If the female lays a second clutch, she may continue to care for the first brood while building a new nest and incubating the subsequent clutch. Savannah sparrows exhibit fidelity to their natal sites, where young may return to breed the following year.

Habitat loss and modern agricultural practices threaten nesting savannah sparrows in New Jersey. The amount of suitable habitat has been reduced by the decline of farming, succession and the development of open space. The result is an increase in small, fragmented patches of farmland. These are more vulnerable to nest predation and are less likely to be used by savannah sparrows. On existing farms, modern agricultural practices such as monocultures reduce habitat quality. In addition, earlier and more frequent mowing can result in destruction of nests, eggs, and young.

Active management is needed to maintain grassland habitats for savannah sparrows. Vegetative succession can be suppressed through annual mowing, controlled burns, or light grazing. All these treatments should be implemented outside of the nesting season. Fields should be grazed or burned on a rotational basis to provide habitat for nesting sparrows while implementing management. Controlled burns should be conducted every four years. At grassland restoration sites, a mix of tall and short grasses and forbs should be planted. Finally, vegetated coastal dunes should be protected to provide habitat for wintering sparrows.