Warbling Vireo: Migration Monday

Hi everyone! I’m back! It’s been about a week, but I have a good excuse for why I’ve been away. I was on vacation fulfilling one of my birding dreams. What might that be you ask? You’ll have to wait and see in tomorrow’s post!

In the meantime, it’s Migration Monday! Today’s featured bird is a new edition that I added to my life list yesterday. Dave and I were at Maria B. Greenwald Park and we kept hearing  very rapid, jumbled songs from high in the trees. The songs were coming from all over the place. They  were hard to spot, but we finally found the crooner: a small gray and white bird. It was very plain, so I became concerned. My first thought was: how are we going to id this gray and white bird that has no distinguishing features? So I used my iPhone to make an audio recording hoping it would be useful. And it was; after searching it on Merlin (my Cornell Lab birding app) we had a match: a Warbling Vireo. Turns out its lack of features helped us with this id as well. So without further ado:

Warbling Vireo (Vireo gilvus)

Description:

Warbling Vireos are small songbirds with white underparts and gray-olive upperparts.They lack wingbars, but have pale lores (the region between the eyes and nostril) and faint yellows flanks on the sides of their breast. They have a black stripe through their eyes and white stripe above their eyes. Don’t let their plain plumage fool you; these birds are anything but dull. Warbling Vireos live up to their names. They sing a rambling song from high in the trees which is their most distinctive and one of their most interesting features. Western Vireos and Eastern Vireos were once considered different species.

Warbling_Vireo_m50-1-354_l_1
Warbling Vireo (Image by Garth McElroy/VIREO via Audubon.org

Range:

Warbling Vireos are medium to long-distant migrants, who mainly travel at night. You can find them in the summers breeding in Western Canada and most of the United States, except for the Southeast. They migrate through Texas and Mexico to reach their winter residence of Central America.

Habitat:

Deciduous and mixed woods, usually near some source of water. Western populations tend to breed in canyons, prarielands, and trees of mountains. Eastern populations breed in isolated groves with water nearby. In the winter they spend time in mixed flocks throughout open woods.

Food:

Mainly caterpillars, but eats other insects as well. They will add  berries and fruits to their diets in fall and winter. Warbling Vireos are foliage gleaners who search for food high in the treetops. They search methodically on one leaf before moving on to the next.

Breeding/Nesting:

Males will attract females by spreading his wings, fanning his tail, and strutting/hopping around. Female vireos in the east will build their nests high up in trees, while females in the west build them in shrubs or shorter trees. The nest is made up of different plant fibers and bark. Warbling Vireos have 1-2 brood per year with an average clutch size of 4 eggs. Both parents will incubate the eggs for 12-14 days. The male will usually sing while incubating. Warbler Vireos are a species that are frequently parasitized by Brown Cowbirds. When this occurs the vireos will unknowingly raise the cowbird chick as their own. However, some females in Eastern populations have figured out that there is a cowbird  egg in their nests. These females will puncture the invading egg and roll it out of the nest. Vireo chicks will fledge from the nest 12-16 eggs after hatching.

Warbling-vireo-on-nest-09-0615
Warbling Vireo on its nest (Image by Gary L. Clark via wikimedia commons)

Sounds:

Males sing  a cheerful and dizzying series of notes. The highly-variable songs are approximately 3 seconds long and usually end on a high note. If you want to hear it, check out the sound links on the Cornell Lab of Ornithology’s Warbling Vireo page. The second sound clips sounds like what I heard the other day. You can find the sound clips here.

Fun Facts:

  • Due to the fact that Warbling Vireos avoid areas that are not unbroken forest, it is believed that their populations are larger than they ever were.
  • Warbling Vireo populations throughout the country are so variable that ornithologists have recognized 6 separate subspecies.
  • Some scientists believe that the Warbling Vireo’s song is partly learned as opposed to instinctual. They believe that their jumbled song is partly due to mistakes in the development process of learning the song.

 

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Author: BirdNation

I am an avid birder, teacher, and nature lover. I primarily birdwatch throughout New Jersey and Eastern Pennsylvania.

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