Ten to fifteen years ago, if you wanted to see a Hutton’s Vireo, a trip to the Chisos Mountains in Big Bend National Park would have been the likely nearest venue. For whatever reason, this small vireo is becoming a fairly common bird in the Hill Country, particularly so in the southwest portion. This non-descript, grayish green songbird was first reported in bird census surveys in the Nature Conservancy’s Love creek Preserve near Medina. In recent months several sightings have occurred in Lady Bird Johnson Municipal Park in Fredericksburg, a considerable eastward shift.
Vireos are wren sized insectivores that live in mostly wooded habitats all across our country; some are easterners while others are westerners. A few are found in the central region of the country; our endangered species, the Black-capped Vireo, lives specifically in Texas and in southern Oklahoma. Of the twelve more common species of vireos, the Hutton’s Vireo is a westerner.
Vireos have many similarities to American wood warblers, but for the most part do not have the showy colors and contrasting plumages that the warblers possess. Vireos have more blunted bills than the sharp-pointed bills of their warbler counterparts. The blunted bills are smaller versions of the shrikes’ bills, thereby indicating a possible common position on a limb of the bird family tree with the shrikes. Many vireos have distinct eye-rings and in some species, “spectacles.” Hutton’s Vireos have a broken eye ring. Several vireos have distinct eyebrow lines, unlike the Hutton’s Vireo.
Although birders loosely lump warblers and vireos together, the Hutton’s Vireo is very similar to the Ruby-crowned Kinglet, a very common winter resident in Texas. Apart from the kinglet’s red crown spot, which is not always visible, the Hutton’s Vireo’s very non-descript plumage features wing bars, but little else. The grayish olive plumage is lighter than the kinglet’s greenish gray plumage. The Hutton’s Vireo has a thicker blunted bill in contrast to the kinglet’s tiny pointed bill. The vireo has two white wing bars to the kinglet’s one bar.
Ruby-crowned Kinglets are hyperactive birds with a persistent wing flick. The bird often hovers while pursuing its insect prey. Hutton’s Vireos similarly pursue their prey, but at a much slower pace. Think of the kinglet’s active life style producing a leaner, slimmer profile than the slower moving plump-shaped vireo. The broken eye ring of the Hutton’s Vireo causes the vireo to appear to have a mad look on its face.
Back to the question concerning the Hutton’s Vireo’s recent appearance in the Hill Country, could it be that the vireo is often mistaken or presumed by birders to be a Ruby-crowned Kinglet? They live in the same wooded habitat and occupy the same mid to high level niche in the forest canopy; possibly the birder with a quick glance, thinks “kinglet” and moves on to the next bird. This could be the case in the winter season when both birds occur in the Hill Country; however, but kinglets move north to breed in the summer while the vireo remains here as a permanent resident.
Another possibility is that the Hutton’s Vireo has shifted its range eastward into similar habitats found in the Trans-Pecos Region. Several birds have moved their ranges over the past twenty-five years, such as White-winged Doves, Greater Kiskadee Flycatchers and Black-bellied Whistling Ducks.. Global warming is often cited as one of the reasons for the shifting bird ranges, but more specific data will be needed to discern likely theories for these shifts. The correct answer may not be known without extensive research, but we birders can always ponder interesting changes in ranges.
It will be easier to identify the Hutton’s vireo in the spring to fall months when the similar Ruby-crowned Kinglets are up north. If you know the Hutton’s call or song, the identification process becomes much easier. If you see the bird after May and before November, it will likely be a Hutton’s Vireo. From November to May it will likely be a Ruby-crowned Kinglet. During the overlap periods look for a nervous twitch; with the twitch it will be a kinglet and without it the bird will likely be a vireo. Sometimes we birders become complacent about really looking closely at similar birds, presuming them to be a common species, in this case, the Ruby-crowned Kinglet.