Savannah Sparrow Life History

Habitat

On both their summer and winter ranges, Savannah Sparrows live in grasslands with few trees, including meadows, pastures, grassy roadsides, sedge wetlands, and cultivated fields planted with cover crops like alfalfa. Near oceans, they also inhabit tidal saltmarshes and estuaries. In Alaska and northern Canada, they live among the shrubby willows of the tundra.Back to top

Food

During the breeding season, Savannah Sparrows eat nutritionally rich insects and spiders. They stalk through grassy areas or along beaches in search of beetles, grasshoppers, and other bugs, as well as spiders, millipedes, and pillbugs, snapping them up in their bill and swallowing them whole. When white frothy spittle masses appear on goldenrod plants, Savannah Sparrows hop up on the plant and devour the spittlebug nymphs inside the foam. On their winter range, Savannah Sparrows switch to a diet of mostly small seeds from grasses and forbs. Along coastal areas, they may eat tiny crustaceans. Back to top

Nesting

Nest Placement

Savannah Sparrows hide their nests amid a thick thatch of the prior season’s dead grasses in densely vegetated areas. The nest is usually on the ground or low in grasses, goldenrod, saltmarsh vegetation, or low shrubs such as blueberry, blackberry, rose, and bayberry. The female selects the nest site, often choosing a spot on the edge of her mate’s territory, thus forcing him to defend new areas and causing conflict with a neighboring male.

Nest Description

The female builds the nest in one to three days. The nest is about 3 inches across and composed of two parts: an exterior of coarse grasses and in the middle, a finely woven tiny cup of thin grass. This inner cup is about 2 inches across and 1 inch deep.

Nesting Facts

Behavior

Like many grassland sparrows, Savannah Sparrows walk along the ground to forage for bugs, occasionally running or hopping to seize prey. Flights are typically quick and low among grasses. At the outset of the breeding season, males perch on the outer limbs of shrubs and trees or atop fence posts to sing and declare their territory. They also use these vantages to keep watch over their area. If another Savannah Sparrow enters a male’s territory, he may use a “flutter flight” display to scare him away—fluttering up with his tail cocked and legs dangling, beating his wings slowly to hover in the air. Males also raise their wings vertically behind their backs in a territorial display, as well as chase intruders off their territory. Males engage in a similar type of flutter-flight display above females during courtship. In the middle and southern parts of their range, many Savannah Sparrow males breed with more than one female, though in the north of their range Savannah Sparrows tend to be monogamous (perhaps because the male’s help is needed at the nest for raising young quickly in a short northern summer). Leading up to winter migration, Savannah Sparrows gather in large flocks and become increasingly restless until one night, they depart.Back to top

Conservation

Savannah Sparrows are widespread and abundant but their populations declined by about 45% between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 170 million and rates them 8 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Savannah Sparrow likely benefited from human changes to landscapes that cleared forests and opened up pasturelands early in the twentieth century, but they may have lost ground due to the urbanization that followed and the shift in agricultural practices that favored intensive row-cropping for corn and soybeans instead of dairy farms and hayfields. Owing to their foraging style, these sparrows are susceptible to some crop pesticides and may eat granular pesticides that are scattered in cornfields. Savannah Sparrow nesting can be disrupted when grassy areas are mowed, or fields hayed before their young have fledged. Overgrazing by expanding populations of Snow Geese in northern Manitoba may be reducing suitable habitat for Savannah Sparrows there.

Credits

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

Wheelwright, N. T. and James D. Rising. (2008). Savannah Sparrow (Passerculus sandwichensis), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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