The olive-sided flycatcher, or Contopus borealis, is a big-headed flycatcher that sits bolt upright on the top of the highest branch of the trees. As if to ensure that birders notice it, the bird calls "pip-pip" loudly.
Adults are dark olive on the face, upperparts and flanks. They have light underparts, a large dark bill and a short tail.
This flycatcher feeds, as most flycatchers do, on insects. In summer, a high percentage of these insects are various wasps, flying ants, and bees. It also eats beetles, grasshoppers, moths, and others. Usually, it forages by watching from a high, exposed perch, and then by hawking.
The nest of the olive-sided flycatcher is usually in a tree on a horizontal branch well out from the trunk. They prefer conifers, but sometimes will nest in deciduous trees. Also, the height of the nest is quite variable, ranging from 5-70 feet above ground. It is usually well hidden among dense twigs or needles.
The nest, usually built by the female, is composed of twigs, grass, weeds, and lined with finer materials. It is a flat open cup.
The female lays 3 eggs that are white to pinkish, with brown and gray spots. The female incubates for 17 days. When the young hatch they are fed by both parents. At 21-23 days old, the young take their first flight.