Wood Thrush – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

May 13, 2025May 13, 2025

Nest Builders at Work

For many animals, an adequate shelter is paramount for their successful reproduction. Here’s a sample of some of the lower Susquehanna valley’s nest builders in action…

Pileated Woodpecker Excavating Nest — Many of our year-round resident bird species get a head start on the breeding season as cavity nesters. Some of these mated pairs use naturally occurring hollows, while still others take advantage of the voids left vacant by the more industrious previous occupants. Woodpeckers in particular are responsible for excavating many of the cavities that are later used as homes by a variety of birds and mammals to both rear their young and provide winter shelter. Pileated Woodpeckers, like other members of the family Picidae, have an almost mystic ability to locate diseased or insect-infested trees for selection as feeding and nesting sites. In this composite image, a pair is seen already working on a potential nursery during mid-January. After use by the woodpeckers, abandoned cavities of this size can become nesting sites for a variety of animals including bees, small owls, Great Crested Flycatchers, Wood Ducks, Hooded Mergansers, and squirrels.

Downy Woodpecker at Nest — After use as a nesting site, a void excavated by Downy Woodpeckers can be occupied in subsequent years by chickadees, titmice, nuthatches, wrens, and other cavity-dwelling species.

Muskrat with Leafy Twig — This Muskrat (*Ondatra zibethicus)* with a leafy twig in tow takes advantage of spring’s new growth to construct or repair its house,…

Muskrat House — A Muskrat house in March. In the absence of leafy twigs, dried cattail stems will suffice. As it ages and decays, the house’s organic matter generates heat and makes an ideal location for turtles to deposit and hatch their eggs.

Soon after Neotropical migrants begin arriving in the forests of the lower Susquehanna watershed, they begin constructing their nests. The majority of these species build “outdoors”, not within the confines of a tree cavity. Here we see a Wood Thrush with its bill full of dried leaves and other materials…

Wood Thrush Nest — …ready to line the cup of its nest in the fork of a small understory tree.

Though it often arrives during early April after spending the winter in sub-tropical and even some temperate climes, the Blue-gray Gnatcatcher must wait to start construction of its nest until many of the Neotropical migrants arrive in early May.

Blue-gray Gnatcatchers — Back at the nest site…

Baltimore Oriole with Nesting Material — Baltimore Orioles weave one the most unique nests of any species occurring in eastern North America.

Baltimore Oriole Nest — Unfortunately for them, man-made litter can often seem to be the ideal material for binding the nest together. In an area only sporadically visited by anglers, this oriole had no trouble finding lots of monofilament fishing line, trash that can fatally entangle both adult and young birds of any species. If you see any fishing line at all, please pick it up and dispose of it properly.

Baltimore Oriole — Always keep an eye open for fishing line and get it before the birds do!

Like many other avians, male Brown-headed Cowbirds are now relentlessly pursuing females of their kind.

Watching and waiting. The Indigo Bunting evades cowbird parasitism by first recognizing the invader’s egg. They then either add a new layer of nest lining over it or they abandon the nest completely and construct a new one. Some patient buntings may delay their breeding cycle until after cowbird courting behavior ceases in coming weeks.

May 8, 2024May 14, 2024

A Pre-dawn Thunderstorm and a Fallout of Migrating Birds

In recent days, the peak northbound push of migratory birds that includes the majority of our colorful Neotropical species has been slowed to a trickle by the presence of rain, fog, and low overcast throughout the Mid-Atlantic States. Following sunset last evening, the nocturnal flight resumed—only to be grounded this morning during the pre-dawn hours by the west-to-east passage of a fast-moving line of strong thundershowers. The NOAA/National Weather Service images that follow show the thunderstorms as well as returns created by thousands of migrating birds as they pass through the Doppler Radar coverage areas that surround the lower Susquehanna valley.

Sterling, Virginia, Doppler Radar west of Washington, D.C., at 4:00 A.M. E.D.T. indicates a dense flight of northbound migrating birds located just to the south of the approaching line of rain and thunderstorms over the State College, Pennsylvania, radar coverage area. (NOAA/National Weather Service image)

More northbound birds are indicated at 4 A.M. by the radar station located at Dover, Delaware… (NOAA/National Weather Service image)

…and by the Mount Holly, New Jersey, radar site. (NOAA/National Weather Service image)

Many of the migrating birds shown here over the Binghamton, New York, radar station at 4 A.M. probably overflew the lower Susquehanna region earlier in the night. (NOAA/National Weather Service image)

And these birds over Albany, New York’s, radar station at 4 A.M. are mostly migrants that passed north over New Jersey and easternmost Pennsylvania last evening and during the wee hours of this morning. (NOAA/National Weather Service image)

Just after 4 A.M., flashes of lightning in rapid succession repeatedly illuminated the sky over susquehannawildlife.net headquarters. Despite the rumbles of thunder and the din of noises typical for our urban setting, the call notes of nocturnal migrants could be heard as these birds descended in search of a suitable place to make landfall and seek shelter from the storm. At least one Wood Thrush and a Swainson’s Thrush (Catharus ustulatus) were in the mix of species passing overhead. A short time later at daybreak, a Great Crested Flycatcher was heard calling from a stand of nearby trees and a White-crowned Sparrow was seen in the garden searching for food. None of these aforementioned birds is regular here at our little oasis, so it appears that a significant and abrupt fallout has occurred.

A White-crowned Sparrow in the headquarters garden at daybreak. It’s the first visit by this species in a decade or more.

Looks like a good day to take the camera for a walk. Away we go!

Along woodland edges, in thickets, and in gardens, Gray Catbirds were everywhere today. We heard and/or saw hundreds of them.

During our travels, American Redstarts were the most frequently encountered warbler. Look for them in low-lying forested habitats.

Many early-arriving Baltimore Orioles have already begun building nests. But widespread territorial fighting today may be an indication that some latecomer orioles became trespassers after dropping in on existing territories during the morning fallout.

Red-eyed Vireos are difficult to see but easily heard in forested areas throughout the Lower Susquehanna River Watershed.

If the oriole isn’t the showiest of the Neotropical migrants, then the Scarlet Tanager is certainly a contender…

The Eastern Wood-Pewee, another forest denizen, has an easy song to learn…a series of ascending “pee-a-wee” phrases interspersed with an occasional descending “pee-urr”. It was one of the few flycatchers we found today, but more are certainly on the way. Their numbers should peak in coming days.

Yellow-rumped Warblers can be especially numerous during migration but tend to peak prior to the arrival of the bulk of the Neotropical species. This was the only “yellow-rump” we encountered today. The majority have already passed through on their way to breeding grounds to our north.

If today you were to visit a streamside thicket or any type of early successional habitat, you would probably find this perky little warbler there, the Common Yellowthroat.

The Yellow Warbler likes streamside thickets too. You can also find them along lakes, ponds, and wetlands, especially among shrubby willows and alders.

Not all songbirds migrate at night. The Bobolink is an example of a diurnal (day-flying) migrant. They’re currently arriving in hay fields that are spared the mower until after nesting season.

There’s obviously more spring migration to come, so do make an effort to visit an array of habitats during the coming weeks to see and hear the wide variety of birds, including the spectacular Neotropical species, that visit the Lower Susquehanna River Watershed each May. You won’t regret it!

Wood Ducks arrived in February and March to breed in the lower Susquehanna valley. Soon after hatching in April or May, the young leave the nest cavity to travel under the watchful gaze of their ever-vigilant mother as they search for food along our local waterways. If you’re fortunate, you might catch a glimpse of a brood and hen while you’re out looking at the more than one hundred species of birds that occur in our region during the first half of May. Good luck!

May 15, 2020August 14, 2023

The Layover

After nearly a full week of record-breaking cold, including two nights with a widespread freeze, warm weather has returned. Today, for the first time this year, the temperature was above eighty degrees Fahrenheit throughout the lower Susquehanna region. Not only can the growing season now resume, but the northward movement of Neotropical birds can again take flight—much to our delight.

A rainy day on Friday, May 8, preceded the arrival of a cold arctic air mass in the eastern United States. It initiated a sustained layover for many migrating birds.

Bobolinks (Dolichonyx oryzivorus) in flocks of as many as fifty birds gathered in weedy meadows and alfalfa fields for the week.

A Bobolink sheltering in a field of Sweet Vernal Grass (Anthoxanthum odoratum) during the rain on Friday, May 8th.

Two of seven Solitary Sandpipers (Tringa solitaria) in a wet field on Friday, May 8. Not-so-solitary after all.

Grounded by inclement weather, Rose-breasted Grosbeaks (Pheucticus ludovicianus) made visits to suburban bird feeders in the lower Susquehanna valley. (Charles A. Fox image)

Freeze warnings were issued for five of the next six mornings. The nocturnal flights of migrating birds, most of them consisting of Neotropical species by now, appeared to be impacted. Even on clear moonlit nights, these birds wisely remained grounded. Unlike the more hardy species that moved north during the preceding weeks, Neotropical birds rely heavily on insects as a food source. For them, burning excessive energy by flying through cold air into areas that may be void of food upon arrival could be a death sentence. So they wait.

A freeze warning was issued for Saturday morning, May 9, in the counties colored dark blue on the map. (NOAA/National Weather Service image)

This radar image from 3:28 A.M. Saturday morning, May 9, indicates a minor movement of birds in the Great Plains, but there are no notable returns shown around weather radar sites in the freeze area, including the lower Susquehanna valley. (NOAA/National Weather Service image)

To avoid the cold wind on Saturday, May 9, this Veery was staying low to the ground within a thicket of shrubs in the forest.

This Black-throated Blue Warbler avoided the treetops and spent time in the woodland understory. He sang not a note. With birds conserving energy for the cold night(s) ahead, it was uncharacteristically quiet for the second Saturday in May.

A secretive Northern Waterthrush (Parkesia noveboracensis) remained in a wetland thicket.

A Scarlet Tanager (Piranga olivacea) tucks his bill beneath a wing and fluffs-up to fight off the cold during a brief May 9th snow flurry.

In open country, gusty winds kept Eastern Kingbirds, a species of flycatcher, near the ground in search of the insects they need to sustain them.

Horned Larks are one of the few birds that attempt to scratch out an existence in cultivated fields. The application of herbicides and the use of systemic insecticides (including neonicotinoids) eliminates nearly all weed seeds and insects in land subjected to high-intensity farming. For most birds, including Neotropical migrants, cropland in the lower Susquehanna valley has become a dead zone. Birds and other animals might visit, but they really don’t “live” there anymore.

Unable to find flying insects over upland fields during the cold snap, swallows concentrated over bodies of water to feed. Some Tree Swallows may have abandoned their nests to survive this week’s cold. Fragmentation of habitats in the lower Susquehanna valley reduces the abundance and diversity of natural food sources for wildlife. For birds like swallows, events like late-season freezes, heat waves, or droughts can easily disrupt their limited food supply and cause brood failure.

For this Barn Swallow, attempting to hunt insects above the warm pavement of a roadway had fatal consequences.

Another freeze warning was issued for Sunday morning, May 10, in the counties colored dark blue on this map. (NOAA/National Weather Service image)

This radar image from 4:58 A.M. Sunday morning, May 10, again indicates the absence of a flight of migrating birds in the area subjected to freezing temperatures. Unlike migrants earlier in the season, the Neotropical species that move north during the May exodus appear unwilling to resume their trek during freezing weather. (NOAA/National Weather Service image)

On Sunday evening, May 10, a liftoff of nocturnal migrants is indicated around radar sites along the Atlantic Coastal Plain and, to a lesser degree, in central Pennsylvania. The approaching rain and yet another cold front quickly grounded this flight.

After a one day respite, yet another freeze warning was issued for Tuesday morning, May 12. (NOAA/National Weather Service image)

And again, no flight in the freeze area. (NOAA/National Weather Service image)

The freeze warning for Wednesday morning, May 13. (NOAA/National Weather Service image)

And the nocturnal flight: heavy in the Mississippi valley and minimal in the freeze area. (NOAA/National Weather Service image)

The freeze on Thursday morning, May 14. (NOAA/National Weather Service image)

At 3:08 A.M. on May 14th, a flight is indicated streaming north through central Texas and dispersing into the eastern half of the United States, but not progressing into New England. (NOAA/National Weather Service image)

The flight at eight minutes after midnight this morning. Note the stormy cold front diving southeast across the upper Mississippi valley. As is often the case, the concentration of migrating birds is densest in the warm air ahead of the front. (NOAA/National Weather Service image)

Today throughout the lower Susquehanna region, bird songs again fill the air and it seems to be mid-May as we remember it. The flights have resumed.

Indigo Bunting numbers are increasing as breeding populations arrive and migrants continue through. Look for them in thickets along utility and railroad right-of-ways.

Common Yellowthroats and other colorful warblers are among the May migrants currently resuming their northward flights.

The echoes of the songs of tropical birds are beginning to fill the forests of the lower Susquehanna watershed. The flute-like harmonies of the Wood Thrush are among the most impressive.

Ovenbirds are ground-nesting warblers with a surprisingly explosive song for their size. Many arrived within the last two days to stake out a territory for breeding. Listen for “teacher-teacher-teacher” emanating from a woodland near you.

September 10, 2017September 4, 2019

Yellowlegs for Breakfast

A few nocturnal migrants flew through the moonlit night to arrive at Conewago Falls for a sunrise showing this morning. A dozen warblers were in the treetops and a Wood Thrush (Hylocichla mustelina) chattered away in the understory of the Riparian Woodlands. Three species of shorebirds were in the falls and on the Pothole Rocks: Least Sandpiper (Calidris minutilla), Lesser Yellowlegs (Tringa flavipes), and Greater Yellowlegs (Tringa melanoleuca).

A Greater Yellowlegs (right) and two Lesser Yellowlegs sandpipers dropped by for breakfast.

The diurnal migration was highlighted by a Merlin (Falco columbarius), an Osprey, and a Bald Eagle, each flying down the river. Most of the other birds in the falls seemed content to linger and feed. There’s no need to hurry folks, only trouble lurks down there in paradise at the moment.