Nashville Warbler – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

Okay, so it happened to be cloudy with drizzle at sunrise—not the best conditions for observing birds in the treetops. But that inclement weather effectively grounded the overnight flight of migrating songbirds leading to a really big fallout in the lower Susquehanna valley this morning.

While straining one’s neck to gaze up into the forest canopy, hundreds of migrants including warblers, vireos, tanagers, thrushes, and flycatchers could be seen. Identifying each was impossible.

Here are of few of this morning’s arrivals. Manually setting the camera to a slower shutter speed compensated a little bit for the backlighting caused by cloudy conditions.

Peak numbers of Broad-winged Hawks will pass through the area during the coming two weeks. They most often migrate in groups, with sizes ranging from several individuals to hundreds or even thousands of birds. Despite this being a less than ideal day for riding thermals and gliding off towards the southwest to continue their journey to the tropics, some “broad-wings” ventured aloft and were on their way soon after the drizzle subsided during mid-morning.

A Broad-winged Hawk lifts off from the cover of the forest where it spent the night.

The same Broad-winged Hawk (bottom) and an adult Bald Eagle gain altitude on a thermal updraft before the former glides away toward the southwest.

Rain from the remnants of Hurricane/Tropical Storm Harvey ended just after daybreak this morning. Locally, the precipitation was mostly absorbed into the soil. There was little runoff and no flooding. The river level at Conewago Falls is presently as low as it has been all summer. Among the pools and rapids of the Pothole Rocks, numbers of migrating birds are building.

Mist and a low cloud ceiling created poor visibility while trying to see early morning birds, but they’re here. The warblers are moving south and a small wave of them was filtering through the foliage on the edge of the Riparian Woodlands. One must bend backwards to have a look, and most could not be identified due to the poor lighting in the crowns of the trees where they were zipping about. Five species of warblers and two species of vireos were discerned.

There are increasing concentrations of swallows feeding on insects over the falls. Hundreds were here today, mostly Tree Swallows (Tachycineta bicolor). Bank Swallows (Stelgidopteryx riparia) numbered in the hundreds, far below the thousands, often 10,000, which staged here for migration and peaked during the first week of September annually during the 1980s and 1990s. Their numbers have been falling steadily. Loss of nesting locations in embankments near water may be impacting the entire population. A reduction in the abundance of late-summer flying insects here on the lower Susquehanna River may be cause for them to abandon this area as a migration staging point.

Bank and Tree Swallows by the hundreds were feeding upon flying insects above the waters of Conewago Falls today. Lesser numbers of Northern Rough-winged Swallows *(Stelgidopteryx serripennis)* and Barn Swallows *(Hirundo rustica)* joined the swarm.

Clear weather in the coming nights and days may get the migrants up and flying in large numbers. For those species headed to the tropics for winter, the time to get moving has arrived.

Category: Nashville Warbler

Big Fallout

Harvey Passes By