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…
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.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.This Muskrat (Ondatra zibethicus) with a leafy twig in tow takes advantage of spring’s new growth to construct or repair its house,……a process that can be repeated or renewed as necessary throughout the year.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……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.You see, the Blue-gray Gnatcatcher relies on plenty of web-spinning spider activity to supply the construction materials it needs.A Blue-gray Gnatcatcher pulling apart a spider’s web on a warm May morning.Back at the nest site……the sticky spider webs bind together lichens and small bits of bark……to form a perfect little cup for the nesting Blue-gray Gnatcatchers.Baltimore Orioles weave one the most unique nests of any species occurring in eastern North America.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.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.All his effort is expended in an attempt to impress her and thus have a chance to mate.This male can indeed put all his energy into the courtship ritual because Brown-headed Cowbirds toil not to build a nest. They instead locate and “parasitize” the nests of a variety of other songbirds. After mating, the female will lay an egg in a host’s abode, often selecting a slightly smaller species like a Yellow Warbler or native sparrow as a suitable victim. If undetected, the egg will be incubated by the host species. Upon hatching, the larger cowbird nestling will dominate the brood, often ejecting the host’s young and/or eggs from the nest. The host parents then concentrate all their efforts to feed and fledge only the young cowbird.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.
Can it be that time already? Most Neotropical birds have passed through the Lower Susquehanna River Watershed on their way south and the hardier species that will spend our winter in the more temperate climes of the eastern United States are beginning to arrive.
Here’s a gallery of sightings from recent days…
During the past two weeks, thousands of Broad-winged Hawks, including this adult bird, crossed the skies of the lower Susquehanna valley on their way to Central and South America for our winter.A juvenile Broad-winged Hawk passes into the sunset during its first autumn migration.Blackpoll Warblers are among the last of the Neotropical species to transit the region. They’ll continue to be seen locally through at least early October.Blue-headed Vireos are the October vireo during the fall, the other species having already continued toward tropical forests for a winter vacation.The lower Susquehanna region lies just on the northern edge of the wintering range of the Blue-gray Gnatcatcher, a species found nesting locally among treetops in deciduous woods. Look for their numbers to swell in coming days as birds from further north begin rolling through the region on their way south.Sharp-shinned Hawks delight visitors at ridgetop hawk watches during breezy late-September and early-October days. They allow closer observation than high-flying Broad-winged Hawks due to their habit of cruising just above the treetops while migrating.A Sharp-shinned Hawk glides over a lookout.Late September/early October is falcon time at area hawk-counting stations, the Peregrine Falcon often being the most anticipated species.Pale “Tundra Peregrines”, a subspecies that nests in the arctic, are strictly migratory birds in the Mid-Atlantic States. They are presently passing through on their way to South America. Like Neotropical songbirds, their long flights provide them with the luxury of never experiencing a winter season.This Carolina Saddlebags and other migratory dragonflies, which normally leave the area by mid-September, are still lingering in the lower Susquehanna region, much to the pleasure of the falcons that feed upon them.An male American Kestrel in pursuit of dragonflies found swarming around the lookout at Second Mountain Hawk Watch in Lebanon County, Pennsylvania.A male American Kestrel stooping on a dragonfly.Osprey will be among the birds of prey passing hawk watch sites during the coming two weeks. The first week of October often provides the best opportunity for seeing the maximum variety of raptors at a given site. On a good day, a dozen species are possible.Seeing cinnamon-colored juvenile Northern Harriers is symbolic of the October migration flights.Bald Eagles always thrill the crowd.In addition to raptors, resident Common Ravens are regularly sighted by observers at hawk watches and elsewhere during the fall season.Hawk-counting stations sometimes log movements of Red-bellied Woodpeckers during late September and early October. This species has extended its range into the Lower Susquehanna River Watershed only during the past one hundred years, making these seasonal migration movements a recent local phenomenon.Blue Jays are currently on the move with breeding birds from the forests of Canada and the northern United States moving south. Hundreds can be seen passing a given observation point during an ideal morning.Blue Jays find a pile of peanuts to be an irresistible treat. Provide the unsalted variety and watch the show!
Be sure to click on these tabs at the top of this page to find image guides to help you identify the dragonflies, birds, and raptors you see in the Lower Susquehanna River Watershed…
Damselflies and Dragonflies
Birds of Conewago Falls
Hawkwatcher’s Helper: Identifying Bald Eagles and other Raptors
You’ll want to go for a walk this week. It’s prime time to see birds in all their spring splendor. Colorful Neotropical migrants are moving through in waves to supplement the numerous temperate species that arrived earlier this spring to begin their nesting cycle. Here’s a sample of what you might find this week along a rail-trail, park path, or quiet country road near you—even on a rainy or breezy day.
The Black-throated Blue Warbler is one of more than two dozen species of warblers passing through the Lower Susquehanna River Watershed right now. Look for it in the middle and bottom branches of deciduous forest growth.The Veery and other woodland thrushes sing a melodious song. Veerys remain through the summer to nest in damp mature deciduous forests.The American Redstart, this one a first-spring male, is another of the variety of warblers arriving now. Redstarts nest in deciduous forests with a dense understory.Adaptable inquisitive Gray Catbirds are here to nest in any shrubby habitat, whether in a forest or a suburban garden.Blue-gray Gnatcatchers (Polioptilia caerulea) arrive in April, so they’ve been here for a while. They spend most of their time foraging in the treetops. The gnatcatcher’s wheezy call alerts the observer to their presence.Look way up there, it’s a pair of Blue-gray Gnatcatchers building a nest.The Eastern Phoebe, a species of flycatcher, often arrives as early as mid-March. This particular bird and its mate are already nesting beneath a stone bridge that passes over a woodland stream.Orchard Orioles (Icturus spurius) are Neotropical migrants that nest locally in habitats with scattered large trees, especially in meadows and abandoned orchards.In the lower Susquehanna region, the Baltimore Oriole is a more widespread breeding species than the Orchard Oriole. In addition to the sites preferred by the latter, it will nest in groves of mature trees on farms and estates, in parks, and in forest margins where the canopy is broken.The Warbling Vireo (Vireo gilvus) nests in big trees along streams, often sharing habitat with our two species of orioles.Eastern Towhees arrive in numbers during April. They nest in thickets and hedgerows, where a few stragglers can sometimes be found throughout the winter.The Yellow-breasted Chat (Icteria virens) is a migrant from the tropics that sometimes nests locally in thorny thickets. Its song consists of a mixed variety of loud phrases, reminding the listener of mimics like catbirds, thrashers, and mockingbirds.Thickets with fragrant blooms of honeysuckle and olive attract migrating Ruby-throated Hummingbirds. Look for them taking a break on a dead branch where they can have a look around and hold on tight during gusts of wind.The Eastern Kingbird, a Neotropical flycatcher, may be found near fields and meadows with an abundance of insects. In recent years, high-intensity farming practices have reduced the occurrence of kingbirds as a nesting species in the lower Susquehanna valley. The loss of pasture acreage appears to have been particularly detrimental.Savannah Sparrows (Passerculus sandwichensis) can be found in grassy fields throughout the year. Large parcels that go uncut through at least early July offer them the opportunity to nest.Male Bobolinks have been here for just more than a week. Look for them in alfalfa fields and meadows. Like Savannah Sparrows, Bobolinks nest on the ground and will lose their eggs and/or young if fields are mowed during the breeding cycle.Cattail marshes are currently home to nesting Swamp Sparrows. Wetlands offer an opportunity to see a variety of unique species in coming weeks.Shorebirds like this Solitary Sandpiper will be transiting the lower Susquehanna basin through the end of May. They stop to rest in wetlands, flooded fields, and on mudflats and alluvial islets in the region’s larger streams. Many of these shorebirds nest in far northern Canada. So remember, they need to rest and recharge for the long trip ahead, so try not to disturb them.
