Rose-breasted grosbeaks (Pheucticus ludovicianus) are not particularly uncommon, but I don’t seem to encounter them very often. My first recollection of a meeting took place about 20 years ago on the Backbone Ridge Trail in the Finger Lakes National Forest in Hector, N.Y. The forest there is a relatively recent phenomenon in the sense that it was nearly all farmland as recently as the 1930s. Between 1938 and 1941 the federal government bought up farms and let some of them go back to woodland and maintained others as grassland. The resulting patchwork of habitat supports a rich community of birds (and other plants and animals). The hedgerows in the fields, for example, are home to most of the brown thrashers that I have ever seen.
But I met the rose-breasted grosbeak in the forest proper, a woodland of second-growth deciduous trees that covers the ridge between Cayuga and Seneca lakes through most of the town of Hector. It is a forest that feels entirely different from the New England forests that I grew up with. For one thing, the natural floral community of the Finger Lakes region is more of a Carolinian assemblage—nearly all deciduous with a few pines here and there—compared to the Allegenian assemblage of central New Hampshire: a robust mix of deciduous and coniferous. In addition, much of the farmland of New Hampshire was abandoned after the Civil War, giving them a 70- or 80-year head-start on the forests of the Finger Lakes. Finally, there are few stone walls in central New York. The geology is sedimentary, and the Pleistocene ice sheets crushed the rock into silt and clay; there are very few boulders and cobbles lying around for farmers to drag to the edge of fields and pastures.
The preferred habitat of P. ludovicianus is described as “open deciduous woodlands.” The forest of the Finger Lakes is unfortunately kept more open than it should be by hordes of white-tailed deer. The combination of woodlot and open field is perfect for them, and there is relatively little hunting in the region (compared to New England). Consequently, it is not unusual to see literal herds of deer as you drive through the countryside. In some locations they have decimated the understory, leaving nothing alive except garlic mustard. The entire next generation of trees is missing.
My Wilmot sighting of a male at this time of year is about right. The Atlas of Breeding Birds of New Hampshire states that they typically arrive during the first two weeks of May and the males arrive a few days before the females. I have not seen this species in my neighborhood before, so I’m not sure whether the male I saw was passing through or staying.
There is striking sexual dimorphism in this grosbeak. The male has a black head, back and tail with a white rump and white patches on its black wings, on the wing coverts, primaries, and secondaries. His undersides are white with a triangular red “bib” on the chest and patches of red under the wings. The large bill is white.
The female grosbeak resembles nothing so much as a large female house finch, all brown and white streaks on the body with a wide white line over the eye. But her larger size (8 inches long) distinguishes her from sparrows and most streaked finches. The female rose-breasted, however, looks very similar to the female black-headed grosbeak (P. melanocephalus), and the two species occasionally hybridize. Although their normal ranges do not overlap, many individual instances are known of one breeding in the other’s distribution (see Sibley). Most hybrids are seen in the Dakotas, where populations of both species are small because of the scarcity of trees.
Nest height ranges widely but is usually in a sapling. One Ontario study of 50 nests found them from between 3 and 50 feet above the ground, with an average of ~20 feet. The nests themselves are somewhat flimsy, composed of loosely woven twigs except for the inner cup, which is made of finer grasses. It is usually placed in a fork or upright crotch rather than on a horizontal limb. During the day, the male incubates the eggs about one-third of the time, but at night only the female stays on the nest.
Rose-breasted grosbeaks are foliage gleaners—although they occasionally hawk for insects—and spend much of their time well above the forest floor, searching through the leaves at the ends of branches in order to pick their prey from the surfaces. During the nesting season they eat mostly insects and during migration they switch over to a largely fruit diet. During the late spring and early summer, they forage throughout the canopy for insects and then drop down into the subcanopy in late summer when those tree species begin to bear fruit.
Given their tendency to remain in the canopy much of the time, they are not seen as often as, say, a robin or any of the ground foragers. But they are frequently heard, and their song is often compared to that of a robin. Like that species, the song is a series of warbled phrases, but the tone of the grosbeak is sweeter and cleaner than that of a robin. As a thrush, the robin’s talent is to be able to sing two notes at once, but Turdus migratorius does not have the dramatic sustain of the brown Catharus thrushes. The female rose-breasted also sings while she is building the nest and when she and her mate are exchanging places while brooding their eggs.
My column last week was a downer about the decline in the numbers of many species over the last 50 years. The rose-breasted grosbeak remains generally common, with an estimated population of 11 million, but has decreased in numbers where its forest habitat has become fragmented. It is also a popular cage bird on its winter range in Latin America and the Caribbean.
Bill Chaisson has been a birdwatcher for over 50 years. He lives and works in Wilmot.
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