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Guide to Species Groups Because BFL covers species from several taxonomic groups, it’s important to know a little bit about the identification, ecology, and behavior of each group before going into the field. Learning a little about each species group will allow you to quickly and accurately interpret your observations. The purpose of the this section is to cue you in on important behaviors or observations that relate to responses you might see while conducting the survey protocol. There is a detailed description of each species in the Species Accounts, with information on distributions, vocalizations, behaviors, and ecology. For example, when reading the taxonomic summaries below, if you are unsure about the sound or context of a hawk begging call, you could refer to the Sharp-shinned Hawk species account for a thorough description. In the summaries below, we often discuss sexual dimorphism. This term refers to differences that occur between the sexes of a given species. For example, when we say that warblers exhibit sexual color dimorphism it simply means that there is some difference in plumage color between males and females that allows us to distinguish the sexes. Hawks All hawk vocalizations are defined as calls, not songs, which are sometimes heard overhead, above the forest canopy. Begging calls from fledglings are often obvious. We are interested in the forest hawks, which include the Broad-winged Hawk, Red-shouldered Hawk, and accipiters. Hawks exhibit sexual size dimorphism, with the female larger than the male, but do not exhibit color dimorphism. In some species, both sexes can occur in light or dark forms, so we recommend studying a field guide to distinguish between the two, as well as to learn the distinctive body shapes of different groups and species specific behaviors. Hawks are often seen soaring or in flapping flight, so learning flight profiles is very important. The shape of the bird and the way it flies are generally the best clues to its identification. The Broad-winged and Red-shouldered hawks are buteos, which tend to soar with open, flat wings, while accipiters fly with more rapid wingbeats. Hawks will often approach quietly to assess what’s going on, so stay alert if they respond to your playback. Alternatively, they may leave an area in response to mobbing calls because they believe potential prey have been alerted to their presence. Also, keep an eye out for their stick nests high in the canopy. Some squirrel species build similar sized nests; unlike hawks, however, their nests are mostly constructed of leaves. Note that fledglings remain with adults for weeks after leaving the nest, so look for family groups in late spring to mid-summer. A comparison of
Sharp-shinned and Cooper's Hawks Sharp-shinned and Cooper’s hawks are two of the most difficult raptors to tell apart in the field because they have such similar plumages. One of the most noticable differences between them is their size. When the birds are flying, veteran hawk watchers look for the long rounded tail of the Cooper’s Hawk as compared to the shorter, squared-off tail of the sharp-shin. Another excellent field mark is neck length. In flight, the Sharp-shinned Hawk’s head does not extend past the leading edge of the wing, giving this hawk a "short-necked" appearance. The Cooper’s Hawk’s head, on the other hand, extends past the leading edge of the wing, giving this hawk a comparatively "long-necked" appearance. A perched accipiter, however, is a real identification challenge—even when it is as close as your bird feeder. A perched bird’s size can be surprisingly difficult to judge, and to make matters worse, both species exhibit reverse sexual dimorphism—that is, the females are considerably larger than the males. A male sharp-shin may be as small as a jay, and a female Cooper’s may be larger than a crow, but a female sharp-shin and a male Cooper’s may appear to be the same size. A perched Sharp-shinned or Cooper’s hawk can be identified by a combination of subtle field marks. The information in the table below comes from two excellent raptor identification field guides: A Field Guide to Advanced Birding, by Kenn Kaufman, and A Field Guide to Hawks, by William S. Clark, illustrated by Brian K. Wheeler. Although none of the field marks listed here will cinch an identification by itself, you can use a combination of characteristics to increase your confidence in identifying perched raptors.
Woodpeckers Woodpecker vocalizations include calls but not songs. For woodpeckers, drumming serves as the primary mate-attraction and territory-defense sound. Drumming is as distinct as a song, and can often be used alone to identify species. Woodpeckers make irregular hammering sounds as they excavate insects from trees, and sapsuckers produce irregular drumming patterns as they cut sap wells in trees. Note that it is possible and important to distinguish drumming from feeding or nest excavation. Woodpeckers exhibit some sexual color dimorphism. Most males have some red on the head. Please check a field guide for examples. All woodpeckers nest in cavities, and many are very vocal and active in the immediate vicinity of their nest hole. Woodpeckers have a distinct flight pattern: a quick flitter of wings followed by a short tuck with no flapping that gives their flight an undulating, wavy pattern.
Thrushes Thrush vocalizations include songs, performed mainly by the male, and distinctive call notes. Thrushes are often heard calling or singing more frequently than they are seen. Thrushes also give a "whisper song," or a softer, quieter version of their primary song. This may serve as an attempt to disguise their location, making it seem as though they are farther away than they are. The spotted thrushes are best identified by face and breast pattern and overall color, including the flanks. The only thrush that exhibits sexual color dimorphism is the Varied Thrush. See Table 6 for a thrush identification guide to help you in the field. Warblers Some warbler species remain high in the canopy or are frequently hidden in the understory, so learning the songs and calls of these species is often the best way to identify them. Songs are high pitched notes and trills, performed mainly by males, sometimes from a conspicuous perch. Females are typically inconspicuous, and are more difficult to see during nesting because they don’t sing. Call notes and alarm chips are given by both males and females. Warblers usually exhibit sexual color dimorphism, with the female’s plumage generally being a duller version of the male’s. Although warblers move from the understory to the canopy, the area where a warbler is seen feeding is often a good key to its identity. Check the individual Species Accounts for species specific behaviors. NuthatchesDistinctive nuthatch behavior includes creeping along tree trunks like woodpeckers. Unique to nuthatches, however, is the ability to climb from the top to the bottom of the tree, head down, frequently craning their neck backwards for a better view of their surroundings. Nuthatches use their strong, sharp bill to probe into furrows of tree bark. They also feed on insects at the tips of tree branches and on seeds of pine cones. Nuthatches are secondary cavity nesters and often use abandoned woodpecker holes as a nest site. The lack sexual color dimorphism makes it difficult to determine gender by plumage. Flycatchers Flycatchers' short simple songs are perhaps the most reliable method of identifying the similar looking species in this group. They exhibit little sexual color dimorphism and, because catching insects is a solitary pursuit, flycatchers are frequently seen alone. Individuals typically sit erect on an exposed perch, flicking their wings and tails, while waiting for a passing insect. After darting out to catch their prey, they return to their perch to try again. Other birds, including warblers, also flycatch, but are rarely as patient and persistent as flycatchers. Look for wood-pewees high in the forest canopy. Olive-sided Flycatchers are frequently seen flycatching from a dead snag in a forest clearing or bog. The Empidonax flycatchers (including the Willow and Acadian flycatchers) are best identified by voice because their plumage and other characteristics are so similar. Flycatchers can be separated from warblers and vireos by their sit-and-wait foraging behavior, their distinctive vertical profile when perched, and physically by their large triangular heads. Vireos Different species of vireo are often confused with each other and can easily be confused with warblers. A vireo’s bill is more "swollen" than a warbler’s and has a slightly hooked tip that is difficult to see at a distance. Songs, mostly sung by the male, are useful in identifying species. Adults show little sexual color dimorphism. Chickadeess The only chickadee studied by BFL is the Chestnut-backed Chickadee. This species is similar in behavior to other species of chickadees, but with a slightly different song and call. It is also easily distinguished by its chestnut back and flanks. Cuckoos The only cuckoo studied by BFL is the Yellow-billed Cuckoo. The bill color, tail pattern, and eye ring are the best ways to separate the Yellow-billed from the Black-billed cuckoo where the two species overlap. Cuckoos are sometimes difficult to see as they stealthily pluck caterpillars in dense, leafy trees. They are never seen in flocks and are very secretive, seldom straying far from cover and thus best identified by voice. They are often seen darting between patches of cover, so pay attention to shape and plumage to distinguish cuckoos from thrashers and other similar species. Titmice Titmice are similar in behavior to chickadees, but slightly larger. The facial pattern of the Bridled Titmouse is striking and distinctive. The Oak Titmouse was formerly considered a sub-species of the Plain Titmouse, and as the name suggests, this species exhibits no distinctive markings except its crest. Orioles The only oriole studied by BFL is the Scott’s Oriole. The male’s black breast and back are distinctive. The adult female is more easily confused with other female orioles, particularly female Hooded and Orchard orioles where their ranges overlap. Scott’s Orioles are often located by following their call note, a sharp chuck.
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