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