By Bill Chaisson
This morning we were walking the dog in Moody Park in Claremont, and I was surprised to hear a veery, one of my favorite thrushes. I was surprised on three counts. First, we have been walking in the park through the spring and I had never heard a veery before. Songbirds generally are more enthusiastic singers in May and June, when they are defending their territories and in the early stages of building a nest and raising their young. By now most species are either on their second brood or are feeding nestlings or fledglings from the first brood. Some species may even be finished breeding entirely.
Second, it was after 9 a.m. and the heat was already building. Many birds tend to sing early in the morning, starting before sun-up and tapering off before 8 a.m. Toward dusk they begin singing again. This is especially true of the thrushes, which often sit high up in threes and let fall their double-timbre notes in the most humid part of the day. (When I applied for a burn permit I found out that I am only allowed to have a fire after 5 p.m. because firefighting research has determined that this is the time of day with the greatest amount of moisture in the air.)
Finally, the veery was in the cut-over parcel up the hill from the Moody Park access road. Among the thrushes, I associate the veery in particular with wet, even swampy woodlands. So, I would have expected to hear its song drifting up from the steep wooded gulches downhill from the access road where Gully Brook heads up. I have been hearing a wood thrush song emanating from that area.
I have been referring to “the thrushes” but the species I have in mind are often called “the brown thrushes” or “the spotted thrushes.” The most familiar members of the thrush family, the Turdidae, are the robin and the bluebird. The juveniles of both these species, particularly the robin, have spotted breasts, but these are molted when they grow into their adult plumage. This resembles the phenomenon observed in the big cats. Lion kittens, both the African lion and American mountain lion, are spotted, but the spots are lost as the animals mature.
The “spotted thrushes” of North America are in the genera Catharus and Hylocichla. There are two other genera that are spotted, one in Asia and one in Africa. The other 19 genera look more like the robin and bluebird in that they are generally bright colored and their plumage is often boldly patterned.
The retention of juvenile characters into adulthood is called neoteny. Catharus and Hylocichla seem to have retained into adulthood the appearance of the juveniles of the “true thrushes,” the genus Turdus, which includes the American robin.
The wood thrush (Hylocichla mustelina, the only member of the genus) is the most striking looking of the North American spotted thrushes. It has large bold brown spots on a bright white chest and belly. Its back and tail are a rich brown and the head is reddish brown. It has a distinct, but incomplete white eye ring and its eyes are large and dark. You can see it is related to the robin by the similarity in the shape of the bill and its long strong legs on which it hops rather than walks.
The rest of our spotted thrushes are in the genus Catharus. They are all smaller than the wood thrush and they are distinguished from each other in part by the extent of their spotting, although the most reliable “field mark” is their voices, which are all distinctive and each singularly beautiful in its own way.
The hermit thrush has a brown back and head with a more rufous-red tail. The spots on its chest are smaller than those of the wood thrush and they fade toward the belly and on the sides. The head, back, and tail of the veery are a reddish brown, but the spotting below is even less extensive than that of the hermit thrush.
So, these three thrushes can be distinguished by the distribution of rufous-red: veery, head, back and tail; hermit , tail; and wood, head. The veery also has a distinctive song that gives it its name: the slurred veer-veer-veer spirals downward because each repetition is at a lower pitch. In contrast, the Swainson’s thrush, which is a uniform grayish-brown on the head, back and tail, has a song that spirals upward as each phrase is issued at a higher pitch. The Swainson’s has a more northerly distribution and lives in coniferous forests, while the other three species tend to inhabit deciduous forests.
In the United States, the Bicknell’s thrush breeds only in the high peaks of the Adirondacks, Green and White mountains and the Katahdin region of Maine. It is very similar to Swainson’s thrush; it lives in the same coniferous forests of the northern mountains, has the same amount of spotting on the breast and a similarly grayish-brown head, back, and tail. The Swainson’s thrush, however, has a yellowish wash on the feathers of its face, throat and chest that the Bicknell’s lacks. They also have quite different songs. The Bicknells is a three-part song like that of the wood thrush, but while the tones of the wood thrush are clear and bell-like, those of the Bicknell’s are whirring and slurred, ending in drawn-out note that is either flat or rising in pitch.
The Bicknell’s thrush was considered a subspecies of the gray-cheeked thrush until 1995. The latter species is broadly distributed across the northern coniferous forests of Canada and does not breed in the United States at all. The Bicknell’s was thought to be a relict subspecies, left behind as the coniferous forest retreated northward after the last ice age, hanging on only in the higher elevations.
The songs of all of these birds are unusually beautiful because they sing two notes simultaneously (double timbre). In the case of the wood thrush and the hermit thrush these notes are clear and separated by dramatic intervals that make each one seem to ring in the air. The Swainson’s song also includes dramatic phrasing but some of the notes are blurred around the edges. The veery and the Bicknell’s songs include the most slurring, but the harmonic quality is still present and there are always pauses before they repeat their entire song. The pauses will leave you standing there in the twilight, waiting. Holding your breath, and waiting.