The English word oriole is derived from the Latin aurum, or gold. It’s a popular name, applied to more than 30 species in the blackbird family (Icteridae) and to about 25 species in the unrelated oriole family of the Old World (Oriolidae). Most orioles, in both families, do wear shades of golden yellow or orange. An exception is the Orchard Oriole of eastern and central North America. Females and young are dull greenish yellow, and adult males are rich, deep chestnut and black.
Orchard Oriole is the smallest of the New World orioles, averaging only about seven inches long. Once, while leading a field trip, I found a dead female on the ground. I asked members of the group to name the species. No one guessed it was an oriole. Most thought it was a warbler, reflecting just how small the bird is.
Adult males are unmistakable if you get a good view, but females and young birds can be confusing. In the East, the challenge is separating them from female Baltimore Orioles. The latter species is larger, of course, and has a distinctly larger bill for its size. Comparing the bill with the width of the head from front to back, the bill of Baltimore Oriole looks at least two-thirds as long as the head. On Orchard Oriole, the bill is barely more than half as long as the head. The more you practice, the more obvious the difference becomes. Even the youngest Baltimore Orioles have more of an orange or brownish tinge than Orchard Orioles, and this is diagnostic in good viewing conditions.
In southern and western Texas, more oriole species overlap, and ID problems also crop up with vagrant Orchard Orioles throughout the western states. Female Orchard and Hooded Orioles are similar in color and markings. The main distinctions between them involve shape. The longer, more curved bill of Hooded Oriole is noticeably different from the short, straight bill of Orchard. Hooded Oriole also has a distinctly longer tail for its size, giving it a slim, elongated look, different from the compact appearance of Orchard Oriole. But young juvenile Hoodeds in summer and early fall start out with shorter bills and tails than adults and can be challenging to separate from Orchard Orioles.
A bird that trips up many birders is the one-year-old male Orchard Oriole. Its plumage is mostly greenish yellow, but it has a sharply defined black mask and throat. Perched up in the open and singing, a young male can be mystifying when you see it for the first time.
What to look for
Size and shape. The smallest oriole, compact and short-tailed.
Bill shape. Short and straight, thick at the base and finely pointed at the tip, without any obvious curve. Only about half the length of the head.
Overall color. Females and young are greenish yellow, lacking any orange tones. Adult males are unmistakably chestnut and black.
Tricky young males. The one-year-old male, seen throughout the spring and summer, is greenish yellow like the female but has a distinct black mask and throat.
The female Orchard Oriole is a perfect demonstration of the importance of looking at bill shape when identifying any bird. Relatively small and yellowish, with two narrow wing bars, this individual might be mistaken for some other bird group. But its bill has a thick pale base and a narrow sharp point, ruling out female Western Tanager, all the warblers, and, in fact, everything except other orioles. Having narrowed the ID down to the right family, we can check the short-tailed look and overall greenish yellow look to be sure of the species. Incidentally, notice the blue-gray legs, a feature shared with the vireos (which are totally unrelated) but not shown by most songbirds.
Over most of the Orchard Oriole’s range, the main ID contender is Baltimore Oriole. Females are superficially similar, and when the two species are not together, the smaller size of Orchard may not be apparent. The strong, pointed bill of Baltimore Oriole looks relatively longer, at least two-thirds as long as the head. Overall color is consistently different: Baltimore with tinges of orange or brown, Orchard looking more greenish yellow. Female Baltimore Orioles are variable in their markings. Most adult females show more black mottling on the back and head than this bird. Some look essentially black-headed, and birders often mistakenly assume that the birds must be young males.
Although Hooded and Orchard Orioles largely separate out by range, they overlap in Texas and New Mexico. Orchard Orioles occur as vagrants throughout the West, and Hooded Orioles have wandered east as far as Ontario. Adult females of the two species are similar. Hooded has a longer bill, on average, and the tip of the bill usually looks more curved. The bird also has a noticeably longer tail than Orchard. Wing pattern is variable on both species and not helpful for ID. The biggest challenge involves juvenile Hooded Orioles in summer and early fall. Shorter-billed and shorter-tailed than adults at first, they can look similar to Orchard Orioles and may be identified only by callnotes.
Most orioles are patterned with bright yellow or orange. The adult male Orchard Oriole, with its rich chestnut tones, is almost unique (a few tropical orioles have traces of the same color), and it’s unmistakable north of the border. The American Ornithologists’ Union currently treats a closely related form — Fuertes’s, or Ochre, Oriole of eastern Mexico — as a subspecies of Orchard Oriole, but some authorities consider it a full species. The adult male Fuertes’s looks like a typical Orchard Oriole, but a rich butterscotch ochre replaces the chestnut. Females and young look almost identical to Orchard Orioles. Fuertes’s Oriole has strayed to South Texas at least once and might be found there again.
Changes in latitude, changes in plumage
Among most oriole species north of the Mexican border — Orchard, Baltimore, Bullock’s, Hooded, and Scott’s — adult males are brightly patterned, while females are more cryptic. North American birders might assume this is the normal way of things, but the majority of the 30-plus oriole species live in the American tropics. In almost all of them, males and females look essentially the same. We see hints of that at our own subtropical edges. In southern Texas, the sexes look the same in Altamira Oriole and almost the same in Audubon’s Oriole. In Spot-breasted Oriole, introduced in Florida, males and females are equally bright.
So our northern species, with their different male and female plumages — exhibiting what’s called sexual dichromatism — are the exceptions to the norm. Scientists believe that the sexes of ancestral orioles looked similar, and that the duller plumages of female orioles in the north evolved later. But why?
Female orioles do more of the work of raising young, and drab plumage makes them less conspicuous to predators. But there are plenty of predators in the tropics, where female orioles still wear bright colors. A major difference is that many tropical orioles maintain a pair bond at all seasons, and both sexes defend a permanent territory. The demands of this lifestyle may outweigh the advantages of camouflage for birds that stay paired up all year.