0 the vesper sparrow (pooecetes gramineus) is a medium-sized american sparrow .
1  it is the only member of the genus pooecetes .
2 adults have light brown upperparts and light underparts , both with darker streaking .
3  they have a white eye ring and a long dark brown tail which shows white outer feathers in flight .
4 their breeding habitat is open grassy areas across most of north america .
5  the nest is an open cup on the ground under a clump of grass .
6 these birds migrate to the southern and central united states and mexico .
7 these birds forage on the ground , mainly eating insects and seeds .
8  outside the nesting season they often feed in small flocks .
9 the male sings from a higher perch , such as a shrub or fencepost , which indicates his ownership of the nesting territory .
10  the musical song begins with two pairs of repeated whistled notes and ends in a series of trills , somewhat similar to that of the song sparrow .
11 this bird's numbers are declining in the eastern parts of its range due to habitat loss .
