Lehigh Valley bird sightings for September 24

Philadelphia Vireo

While birders were scanning the skies last week for hawks, eagles and falcons, an extraordinary number of sightings of Philadelphia Vireos were reported throughout the Lehigh Valley region.

The Philadelphia Vireo is a migratory bird often mistaken at first glance by its common relative, the Red-eyed Vireo. The two species live in the same kind of habitat: deciduous trees such as aspen, willow, alder, ash and maple. But they don't get along very well. They've been known to fight for territory.

Despite its name, the Philadelphia Vireo is almost never seen in the Lehigh Valley except for an occasional sighting during migration in the spring and fall. The bird migrates mostly at night. It spends its days refueling for the flight across the Gulf of Mexico to wintering grounds in Central America, where it is found from the Yucatan Peninsula to Panama.

The Philadelphia Vireo breeds in Canada north of the Great Lakes, with the greatest concentrations found between Quebec and Saskatchewan. It nests in trees. The female produces three to five eggs. Both parents incubate the eggs, which hatch in about 14 days. The young leave the nest 12 to 14 days after hatching.

A comparison: Red-eyed Vireo

Adults are mainly olive-brown on the upper parts with yellow underparts and a gray crown. They have no wing bars and no eye ring but display dark eyes through the dark eyes and a white stripe just above them. 

The diet consists of mostly of caterpillars, moths, beetles, wasps, bees, ants, bugs and some spiders. It is a berry-eater in late summer and fall, when bayberry and dogwood fruit are available. The bird forages mostly in deciduous trees, flitting from branch to branch looking for insects. It often will hover from foliage or hang upside down to feast on insects located underneath twigs.

So where did the Philadelphia Vireo get its name? Other than migration time, the bird is rarely seen in the City of Brotherly Love. It turns out that ornithologist John Cassin collected a specimen of the bird in Philadelphia during the 1851 migration, hence the name. Birders of the era sometimes called it the Brotherly-love Vireo, according to Tennessee's Watchable Wildlife.

Populations of the Philadelphia Vireo appear to have increased between 1966 and 2014, the North American Breeding Survey reports.

Philadelphia Vireo

Regional sightings of the Philadelphia Vireo appear in Dave DeReamus's report for the Eastern PA Birdline, which is sponsored by the Lehigh Valley Audubon Society. The list covers the week ended September 24.

Pen Argyl, Northampton County
Gray-cheeked Thrush: 1 on September 20.

Jacobsburg State Park, Northampton County
Philadelphia Vireo: 2 on September 16 and 1 on September 22.

Williams Township, Northampton County
Connecticut Warbler: 1 on September 23.

Monocacy Nature Center, Northampton County
Philadelphia Vireo, 1 on September 22.

Little Gap, Northampton County
Ruffed Grouse, 1 on September 18.
Philadelphia Vireo, 1 on September 16.

Little Gap, Carbon County
(at the Blue Mountain Ski Resort)
Philadelphia Vireo, 1 on September 18.

Bake Oven Knob, Lehigh County
Osprey, 34 on September 17.
Bald Eagle, 12 on September 17 and 10 on September 20.
Broad-winged Hawk, 1,901 on September 20 and 519 on September 22.
Peregrine Falcon, 2 on September 20 and September 22.
Philadelphia Vireo, 1 on September 16 and September 23.

Long Swamp Township, Berks County
Mississippi Kite, 1 on September 22 (fly-by).

Green Lane Reservoir, Montgomery County
(at the Church Road area)
Black-crowned Night Heron, 1 on September 19.
Snowy Egret, 1 from September 19 through September 22.
American Golden-Plover, 2 on September 22.
Stilt Sandpiper, 1 on September 17 and 2 from September 19 to September 21.
Sanderling, 2 on September 19 and 1 on September 20.

Peace Valley Park, Bucks County
Lesser Black-backed Gull, approximately 50 on September 17.
Forster's Tern, 2 on September 16.
Philadelphia Vireo, 1 on September 17.
Gray-cheeked Thrush, 1 on September 17.

Red-breasted Nuthatches continue to be reported from several sites last week.

To report bird sightings to Dave DeReamus, send an e-mail to becard.com with the word "Birdline" in the subject heading.