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SPECIES ACCOUNT BALTIMORE ORIOLE (Icterus galbula) Vineyard Overview: The Baltimore oriole is a popular and well-known bird on the Vineyard, mainly because of the startling orange plumage of adult males. For many Islanders, the sight of a Baltimore oriole is a special moment – but this is one of those birds that is much more common here than most people would imagine. If you learn to recognize its vocalizations and its short-tailed shape as it flies overhead, you’ll find yourself encountering this oriole everywhere you go. Only adult males feature the eye-catching orange; females and immature birds have a similar pattern but are much duller. And like orioles generally, the Baltimore oriole is a treetop species, often hidden in foliage and often far enough above the ground so that its color doesn’t really show. But these birds are found virtually everywhere there are large deciduous trees. In particular, Baltimore orioles are surprisingly common in densely settled residential neighborhoods, where only a hundred yards or so may separate the nests of different pairs. Baltimore orioles are strongly migratory and vacate the Island entirely for the winter (except for occasional stragglers lingering into December). This species arrives fairly early during spring migration, with the vanguard typically appearing in late April; by mid-May, most of our breeders are back and hard at work with the business of mating and nest-building. And the nests are impressive ones, pendulous sacks woven from grasses and other fibers, usually hanging from the end of a branch in a tall tree. Pairs often Adult male Baltimore oriole. Photo: David Brezinski/USFWS seem to make multiple nests, either for practice, to fool predators, or in case their primary nest is damaged. Identification: Baltimore orioles are about 8 inches long, somewhat smaller than a robin. The bold orange-and-black pattern of adult males is unmistakable, and even females and young birds are clearly orange. The beak is relatively long and sharply pointed. Orchard oriole, a less common, slightly smaller relative that also occurs here, has a similar pattern but with red replacing the orange of a Baltimore oriole on adult males; female and young orchard orioles are yellowish-green. Baltimore orioles are highly vocal birds, with a song consisting of a series a rich, clear, whistled notes. Often single notes or song fragments are given in a long, regularly spaced series. Each individual has a fairly stable repertoire of songs, but the repertoire varies from bird to bird. This means you can learn to recognize the songs of particular birds (perhaps even returning birds from the year before!). But in The Nature Conservancy Massachusetts Islands Office 18 Helen Avenue, Vineyard Haven, MA 02568 Matt Pelikan, Program Manager | [email protected] | (508) 693-6287 Ext. 11 learning the song of the species, there is no consistent pattern to recognize, and you have to rely instead on learning the whistled tone quality of the song. Baltimore orioles also give a sustained chattering call when excited or alarmed. Ecological functions: Baltimore orioles are probably one of the most beneficial of our nesting birds. They are highly insectivorous in the summer, especially when feeding young, and are particularly deft at capturing caterpillars (among which are found many of our most harmful insect pests) from among the foliage of trees. The long, sharp bill is an effective tool for pulling prey out of flowers, bark crevices, or other constricted spots. So this bird is an effective controller of invertebrate populations. While it’s sad to think of a popular bird like the oriole being on the other end of the process, oriole eggs and nestlings are frequent prey items for larger birds such as crows, blue jays, and grackles. Strategies: 1. Provide nesting habitat and material. While there are exceptions, most oriole nests are built near the top of tall trees. So preserving mature deciduous trees in any major landscape overhaul will benefit this species. Oriole nests are constructed from fibers of various kinds, so keeping a portion of your yard unmowed in spring will help ensure a supply of grass stems for these birds to nest with. Orioles will also collect fibers such as pet hair or string, and leaving such items out specifically for use by these birds may be helpful. 2. Limit predation. Given their arboreal habits, orioles are not often caught by mammalian predators such as cats. Still, they’ve vulnerable when foraging or visiting feeding stations, so keeping your cat indoors will help avoid oriole mortality. There is probably little one can do to prevent nest predation by other birds, but you can be confident that orioles have evolved strategies, including vigorous territorial defense and the ability to re-nest if a first set of young are lost, that allow them to tolerate this form of predation. 3. Provide food and water. This strategy may be most effective in early spring, when orioles first arrive and are prospecting for territories. Flowering cherry, apple, or shadbush may help attract arriving orioles to your yard, with the sugar-rich nectar from the flowers probably helping the birds recover from the rigors of migration. Throughout the season, orioles seem drink more water than many other birds, so providing a water source will benefit these birds. In particular, orioles seem to like a drink of water at the very end of the day, and they are willing to take it in the form of water droplets on plants: so simply spraying water on some of your garden plants or shrubs around sunset may be helpful. 4. Reduce mortality from window collisions. Generally at ease around human habitation, Baltimore orioles are at risk for being injured or killed by colliding with windows. Placing decals on windows, to avoid the appearance that the window is empty space, may help reduce this risk. Placing netting outside windows is an even more effective method, though it is more complicated to do and may not appeal aesthetically to a homeowner. Notes: Especially upon their arrival in spring, Baltimore orioles are fond of drinking nectar from flowers (for example, apple blossoms), and will feed on orange halves or even the contents of hummingbird feeders! Orioles are in the blackbird family, and the red-winged blackbird and common grackle are fairly closely related to the Baltimore oriole. Although fairly small birds, Baltimore orioles are fearless in defense of their nests, and it is common to see a much larger crow beating a hasty retreat with one or more orioles in hot pursuit. The deep, bag-like nests of these orioles may be well hidden by foliage and then revealed in fall, when the leaves drop. You may be surprised to find where orioles nested during the past summer – these birds tolerate human activity quite well and often nest very close to houses.