Blackbirds with Some Color

Of A Feather
By Bill Chaisson
It is hard to miss a Baltimore oriole and yet I feel like I go for years without seeing one and feel surprised when I do. My better half reported one at the end of our road, near a home surrounded by mature deciduous trees alongside Kimpton Brook. I have been down there to look for it and haven’t found it. This is surprising because a black and orange bird with a loud song should be hard to miss.

Jim McCormac, a nature blogger in Ohio, writes about the historical nesting habits of Baltimore orioles:

Why the orioles’ preference for elms? Probably for safety’s sake. The spindly, drooping ultimate branches of elms prohibit access [by] many predators. A raccoon would certainly never make it to a nest … Nor would that most effective of avian nest predators, the black rat snake, I would guess. Fortunately orioles have proven to be adaptive, and have jumped the arboreal ship to other trees for nesting purposes. A favorite is the Eastern Cottonwood, Populus deltoides.

This is an co-evolutionary pairing that was not dangerously tight. The oriole preferred elms, but simply moved on when mature trees became scarce after the 1920s because of Dutch elm disease. The dangerous scenario is exemplified by the Kirtland’s warbler and the jack pine. The warbler nests primarily in even-aged stands of nearly pure jack pine. The trees are only acceptable when they are between 5.5 and 16 feet feet tall. Historically, this kind of habitat was produced regularly by wildfire in their northern Midwestern range. Fire suppression policies have made it one of the rarest North American birds.

The Baltimore oriole (Icterus galbula) has a much broader range than the Kirtland’s warbler and a more catholic taste in habitat. The setting at the end of my road is ideal for them: open deciduous woodland of mature trees along a stream or river. But they also favor nesting and

living in villages where there are large street trees. They avoid conifers and prefer the edges of deciduous forests.

Icterids that live in North America, the so-called New World blackbirds, aren’t particularly black all that often. There are five clades in the family. Three include species that live north of the Mexican border: orioles, meadowlarks and their allies, and grackles and their allies. Only the last includes actual black birds. In fairness, the Neotropical clades—the oropendolas and caciques—are mostly black.

We have two orioles in the Northeast. The other is the orchard oriole (Icterus spurius), which is more common in the southeastern states. The very northeast corner of its range is in southeastern New Hampshire. According to the Atlas of Breeding Birds of New Hampshire, this is a relatively recent phenomenon and nearly all records of breeding are along the seacoast, with one in the Merrimack Valley near the Massachusetts border. Ralph Andrews, writing in the atlas, notes that it can be decades between recorded nesting events and also that many of the sightings are of males in their first-year plumage. He suggests that this is evidence that these are “pioneer” birds, extending the range of the species northward, citing observations from Manitoba that document a similar phenomenon in the northwest corner of their range.

There are interesting differences between the two oriole species. I. spurius is smaller and the males are chestnut brown rather than bright orange. The orange of I. galbula and the chestnut of I. spurius covers the underparts, lower back. The orchard has a black tail, the Baltimore orange and black. In both species first-year males resemble the females with subtle differences.

Their nesting habits are different. The orchard oriole does not build the pendant nest like the Baltimore. Instead the females weave a hanging cup, like a large version of a vireo nest. Furthermore, I. spurius is “semi-colonial”; several pairs often nest within close proximity to one another.

Evolution operates in mysterious ways. When I traveled to Chiapas, Mexico and encountered oropendolas, I saw that they build woven pendant nests that are even more

dangling than those of Baltimore orioles, but they were colonial nesters like the orchard oriole. The canonical explanation for these sorts of similarities within a family is that the traits were present in some shared (likely now extinct) ancestor and passed on in both clades, but expressed among the descendants in different patterns and combinations.

Many bird lovers put out oranges to attract orioles. All orioles are attracted to fruit. They are occasionally regarded as pests in this regard when they enter orchards or other agricultural settings. They are, however, primarily insectivorous, especially during the breeding season while they are feeding young. While the orchard oriole is appreciated in the South for eating large quantities of the cotton boll weevil, Baltimore orioles are lauded for consuming hairy caterpillars, particularly the nuisance species like the spongy moth (formerly gypsy moth) and tent caterpillars. Few songbirds eat hairy caterpillars because the indigestible hairs line their stomachs and hinder absorption of nutrients.

Every once in a while a grackle or a red-winged blackbird seems to get off a pretty note. The songs of orioles are the opposite: they are collections of pretty notes and occasionally a grating sound pops out to remind you that orioles are icterids. While the orchard oriole sounds a bit like a robin in a hurry, the Baltimore’s song consists of 5 to 7 “pure, liquid, whistled” notes followed by a long pause and then they are repeated with variations. This can go on for a while. As with the hermit thrush, the pauses provide drama.

While they sometimes sing on the wing, orioles usually give voice high up in a tree from an exposed perch, and they often have favorite branches to which they regularly return. I just need to find the one at the end of my road.

Bill Chaisson has been a birdwatcher for over 50 years. He lives and works in Wilmot. Contact him at [email protected].