Blackbirds with a bit of color |

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It’s hard to miss a Baltimore oriole and yet I feel like I’ve gone years without seeing one and am surprised when I do. My better half reported one at the end of our road, near a house surrounded by mature deciduous trees along Kimpton Brook. I went there to look for it and I did not find 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 of the historic nesting habits of Baltimore orioles:

Why do orioles prefer elms? Probably for security reasons. The last slender and drooping branches of the elms prevent access [by] many predators. A raccoon would certainly never reach a nest… Nor the most efficient of avian nest predators, the ratsnake, I suppose. Fortunately, the orioles proved to be adaptive and jumped from the tree ship to other trees for nesting purposes. A favorite is cottonwood, Populus deltoides.

It’s a co-evolving pair that wasn’t dangerously tight. The oriole preferred elm trees, but simply evolved when mature trees became rare after the 1920s due to Dutch elm disease. The dangerous scenario is illustrated by the Kirtland warbler and jack pine. The warbler mainly nests in even-aged stands of nearly pure jack pine. Trees are only acceptable when they are between 5.5 and 16 feet tall. Historically, this type of habitat was regularly produced by wildfires in their northern Midwestern range. Fire suppression policies have made them one of the rarest North American birds.

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

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

The icterids that live in North America, the so-called New World blackbirds, are not particularly black very often. There are five clades in the family. Three include species that live north of the Mexican border: orioles, meadowlarks and their allies, and common grackles and their allies. Only the last includes real black birds. In fairness, the neotropical clades – oropendoles 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 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 breeding records are along the coastline, including one in the Merrimack Valley near the Massachusetts border. Ralph Andrews, writing in the atlas, notes that there can be decades between recorded nesting events and also that many sightings are of males in their first-year plumage. He suggests this is evidence that they are “pioneer” birds, extending the species’ range northward, citing sightings from Manitoba that document a similar phenomenon in the north-east corner. west of their range.

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

Their nesting habits are different. The Orchard Oriole does not build the nest hanging like the Baltimore. Instead, the females weave a hanging cup, like a large version of a vireo nest. Moreover, I. spurius is “semi-colonial”; several pairs often nest close to each other.

Evolution works in mysterious ways. When I traveled to Chiapas, Mexico, and encountered Oropendoles, I saw that they build woven hanging nests that are even more

pendulous than those of the Baltimore orioles, but they were colonial breeders like the orchard oriole. The canonical explanation for these types of similarities within a family is that the traits were present in a common ancestor (probably now extinct) and passed down in both clades, but expressed among descendants in different patterns and combinations.

Many bird lovers pull out oranges to attract orioles. All orioles are attracted to fruit. They are sometimes considered pests in this regard when they enter orchards or other agricultural settings. They are however primarily insectivorous, especially during the breeding season when they prey on the young. While the orchard oriole is prized in the South for eating copious amounts of cotton boll weevil, Baltimore orioles are lauded for consuming hairy caterpillars, especially pest species like gypsy moth (formerly gypsy moth) and tent caterpillars. Few songbirds eat hairy caterpillars because the indigestible hairs line their stomachs and impede nutrient absorption.

Every once in a while, a common grackle or red-winged blackbird seems to put out a pretty note. The songs of the orioles are the opposite: they are collections of pretty notes and sometimes a creaking sound is heard to remind you that the orioles are icterides. While the orchard oriole sounds a bit like a rushing robin, the Baltimore song is composed of 5 to 7 “pure, liquid, whistled” notes followed by a long pause and then repeated with variations. It may take some time. As with the hermit thrush, the pauses are dramatic.

Although they sometimes sing in flight, orioles usually sing high in a tree from an exposed perch, and they often have favorite branches that they return to regularly. I just need to find the one at the end of my road.

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


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