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Birds of the North Olympic Peninsula

 

Birds of the Lower Dungeness

River Riparian Forest

by Bob Boekelheide

 

The riparian forest of the lower Dungeness River (defined as the region downstream from the Dungeness Fish Hatchery, or the lower 10.5 river miles) provides wonderful habitat for a wide variety of birds.  The lower Dungeness is relatively unique because it has an unbroken mix of mature coniferous and deciduous trees for several miles, including thickets of various shrub and tree species that provide excellent protection for small birds.  Because of the quality and extent of this habitat, the lower Dungeness forest has been officially designated an Important Bird Area by the Audubon Society. 

The riparian forest is probably most important as breeding habitat for songbirds, not only for species that remain throughout the year, such as Song Sparrows and Spotted Towhees, but also for migrants that travel thousands of miles from their wintering areas, such as Wilson’s Warblers and Pacific-slope Flycatchers.  Some of these travelers are known as “Neotropical migrants” because they annually fly between here and the Neotropical zone in Central and South America.  Some of the longest-distance migrants that breed in the Dungeness forest include Swainson’s Thrushes and Yellow Warblers, both of whom may winter as far south as Peru and Brazil.  Not coincidentally, these species are also among the last to arrive in the spring and the first to depart in late summer. 

Regardless of what adult songbirds eat, most of them primarily feed insects to their young.  Clearly, sizable populations of insects that thrive around aquatic habitats and adjacent riparian forests are key to the birds’ breeding success.  One of the basic tenets of the breeding ecology of birds is that they time their egg laying so that their young are fledging when prey populations are at peak availability.  Nothing could be finer for these birds than large hatchings of caterpillers, or lots and lots of crawling and flying insects, during the critical breeding period from April to July. 

Picture the variety of songbirds that prosper near the river and the variety of ways that they obtain insects and other arachnids.  Wee little Winter Wrens stalk the forest floor, picking insects and spiders from the nooks and crannies of downed logs and bushes.  Kinglets, chickadees, and warblers specialize in gleaning insects and spiders off of leaves and twigs in the canopy, whereas creepers and nuthatches pick prey species from the grooves in the bark of trees.   Birds that prey on the wing, such as swallows, swifts, and flycatchers, pick their favorite insects - midges, moths, beetles, and damselflies - right out of the air.   Adult songbirds literally become insect-capturing machines while they feed chicks, spending hours carrying hundreds or thousands of insects to their hungry broods each day.  Although typically not considered songbirds, woodpeckers chip and drill into the bark of trees, gobbling up the grubs and ants from underneath.            

The river itself directly provides food for birds ranging in size from American Dippers to Bald Eagles.  The dippers have a relatively unique niche for a perching bird, diving into swiftly-flowing rivers and streams to capture insect larvae, fish eggs, and small fish.  They are an amazing example of convergent evolution, feeding and moving in the water very similar to the salt-water inhabiting auklets and murrelets.  Shorebirds such as Spotted Sandpipers pick at aquatic insects at the water’s edge when  they stop beside the river.  Diving ducks that breed along the river, Common Mergansers and Harlequin Ducks, are not afraid to dive into deep pools and swift rapids to capture small fish and other aquatic organisms.  And, of course, spawning salmon provide a bountiful feast for scavenging gulls and eagles during fall and winter.

Songbirds that stay through the fall and winter must be resourceful during lean times, able to switch between food sources as they become available.  Robins, for instance, switch around all winter, concentrating one week on snowberries when the fruit ripens to perfection, then searching out old apples in nearby orchards the next, then foraging on grassy lawns if warm, wet weather brings worms to the surface.  Even though we think that seeds and berries provide most of the nutrition for wintering songbirds, there are still some species that rely on insects during the cold season.  The most obvious of these are kinglets and creepers, both of which are able to find insects and spiders in mid-winter by gleaning foliage and tree bark.  Most wintering birds, however, are the typical seed-eaters that remain at northern latitudes, like sparrows and finches, who are able to rely on natural seed sources and nearby feeders if they are available.

The last main group of birds found in the Dungeness Riparian Forest are the higher trophic level predators - hawks and owls.   Some of these, such as Sharp-shinned Hawks, Cooper’s Hawks, and Merlins, specialize in capturing smaller birds.  Others such as Northern Harriers and Red-tailed Hawks concentrate on rodents.   The edge habitats found alongside the riparian forest provides important hunting grounds for these birds.  Great-horned Owls and Western Screech-Owls nest inconspicuously within the forest, occasionally revealing themselves with their hoots and toots during winter and spring.

Make it a point to walk the Railroad Bridge Trail at dawn some fine spring day in May.  The first bird voices you hear will be from species that either stayed all last winter or else arrived very early in the spring, like robins, Song Sparrows, and White-crowned Sparrows.  The long-distance migrants, like warblers, flycatchers, and Black-headed Grosbeaks, seem to wait until the local have had their say, then they, too, begin their morning chorus.  As the day progresses, you will hear Western Tanagers chortling high in the canopy, Bewick’s Wrens singing away in the shrubs, and Warbling Vireos going on and on into the afternoon, repeating their up-and-down songs over and over.  Finally, as quiet evening shadows grow in the deep woods, the ethereal whistles of the Swainson’s Thrush, the best singer of them all, puts the forest to sleep.