Standing on a hilltop in the woodland of the Chilmark moraine this past weekend, I experienced a single, dominant impression: Red-eyed vireo is one seriously common bird on Martha’s Vineyard. One of our later spring arrivals, this unobtrusive species rapidly fills Island forest during the second half of May.
Vireos in general are not well represented here, in terms either of diversity or numbers. As far as I know, eight species of these birds, which resemble sluggish warblers, are known on the Island. Warbling vireo, a drab gray songbird of wetland treetops, is a scarce migrant, and rare, occasional breeder here. White-eyed vireo, a Southern species of thickets and understory that is gradually extending its range northward, may be breeding here in small numbers, but remains uncommon at best. I don’t think blue-headed vireo has ever nested here, but it’s an uncommon if regular passage bird in both spring and fall.
Philadelphia vireo, nearly as drab as its warbling relative, is a rare migrant, found here mostly in fall. Even more scarce is the yellow-throated vireo; despite it being a reasonably common breeder as close as central Massachusetts, I’ve seen only one in 27 years of birding the Vineyard. Bell’s vireo, a shy and unobtrusive vagrant from the West, is known here only from a couple of records, while the subtropical black-whiskered vireo has been found here precisely once.
But red-eyed vireo? Perhaps the most plentiful bird in our deciduous woodlands! In appropriate nesting habitat, you can almost always hear at least one male singing at this time of year, and it’s not surprising to hear four or five at once.
This is a bird you’re far more likely to hear than to see. Its vocal stamina is astonishing, and this species often continues its song through midday, when most other songbirds take a breather. Listen for an endless series of short, conversational phrases: “Pick it up! Slow down. Fed the cat yet? No way.” It’s relentless, but for me, it’s a welcome, soothing song, the soundtrack of a New England woodland on a lazy summer day.
Red-eyed vireos also give a whining call — “Nyahhhh!” — when irritated, and this note can carry as far as the song does. But actually glimpsing the bird making these noises is a different matter. Red-eyed vireos typically call from the lower part of the forest canopy, putting them well overhead, and they are masters at concealing themselves in clumps of leaves. And the bird itself does not attract attention: olive on the back and grayish underneath, this species blends into the leaves and dappled light of a forest.
Once in a while, though, you’ll find one in the open, perhaps singing from a branch or twig. Only when you see one well will any real field marks stand out: a gray cap, a white line over the eye, and a dark line through it, and, if the light is exactly right, the eponymous red iris in the eye. (Warbling, Philadelphia, and Bell’s vireos show faded versions of the same pattern, minus the distinctive eye color; black-whiskered looks very much like red-eyed, with the addition of a strong “whisker” mark on the throat. Blue-headed, white-eyed, and yellow-throated vireos look rather different, sporting wing bars and pale “spectacle” markings on the face.)
The link between this red-eyed vireo and deciduous, preferably moist woodland is a strong one, and these birds rapidly lose interest in habitat as the canopy fragments, the trees get shorter, or the understory thins out. Moreover, this bird strongly prefers broad-leafed trees to conifers. But habitat meeting its preference is plentiful on the Vineyard, dominating the up-Island hills. And the density with which red-eyed vireos inhabit favorable terrain translates to vast numbers; I’d hate to have to offer a precise estimate, but surely our summer population of this species numbers in the thousands.
All the vireos are tidy but secretive nest builders, usually choosing a site well up in a deciduous tree. Often the well-constructed nest, tightly woven and deeply cup-shaped, hangs from a horizontal fork in a small branch. Hard to find during the summer, old vireo nests are often revealed when the leaves fall.
Despite its rather lethargic habits, the red-eyed vireo is a formidable predator of invertebrates, especially caterpillars. Birders of a certain age think of vireos as close relatives of warblers, but modern taxonomy puts them closer to the shrikes, those quintessential predatory songbirds. Like a shrike, a vireo has a blunt-tipped bill with a nasty little hook on the end — a tool quite different from the hookless and fine-tipped bill of a warbler, adapted more for probing than for grabbing. If you get a chance to watch a red-eyed vireo long enough, you’ll eventually see it snag a meal, and you’ll often be impressed by the size of the prey this bird cheerfully manhandles.
It may take patience and a measure of birding skill to actually spot one. But red-eyed vireos are everywhere at this time of year, perhaps the most characteristic bird of one of our most plentiful habitats.
