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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
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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.