0 the olive-sided flycatcher , contopus cooperi , is a passerine bird .
1  it is a medium-sized tyrant flycatcher .
2 adults are dark olive on the face , upperparts and flanks .
3  they have light underparts , a large dark bill and a short tail .
4 the song is a whistled quick-three beers .
5  the call is a rapid pip pip pip .
6 contopus borealis is a junior synonym of contopus cooperi , according to the 1997 aou checklist , quoted by bison .
7  the name of this species is listed as contopus borealis in many older guides .
8 their breeding habitat is coniferous woods across canada , alaska and the northeastern and western united states , and other types of wooded area in california .
9  olive-sided flycatchers are abundant in early postfire landscapes that have burned at high severity .
10 these birds migrate to central america and the andes region of south america .
11 they wait on a perch at the top of a tree and fly out to catch insects in flight .
12 the female usually lays 3 eggs in a shallow open cup nest on a horizontal tree branch .
13  the male defends a large area around the nesting territory .
14  both parents feed the young birds .
15 the numbers of this bird are declining , probably due to loss of habitat in its winter range .
