New feature: MVAS’s Bird of the Month is Bullock’s oriole

This colorful male Bullock’s oriole was photographed at Percha Dam by Mesilla Valley Audubon Society member Patti Rice.
This colorful male Bullock’s oriole was photographed at Percha Dam by Mesilla Valley Audubon Society member Patti Rice.
One of our more spectacular summer residents, male Bullock’s orioles brighten many backyards and parks in southern New Mexico. With their brilliant orange plumage, offset by black and white highlights, these sharp-billed relatives of blackbirds return to our area each April after wintering in western and central Mexico.

They feed and nest in large trees, so older residential neighborhoods, as well as the remnants of native cottonwood forests along the Rio Grande, offer suitable habitat for these colorful songbirds. Males arrive first and establish territories through song and aggressive displays. Females arrive later, choose a mate, and begin to help with territory defense. Soon, the pair starts work on its distinctive nest: a pendulous, sac-like structure that hangs several inches below the branch to which it’s attached.

The female is the primary artist of the nest, weaving together long fibrous material such as grasses, hair, and twine to build the outer shell. The male helps supply the female with building material, including the soft nest lining, which may include feathers and the fluffy seeds produced by cottonwoods and willows. Nest construction takes as long as two weeks; it will be another month before the young orioles emerge from the nest.

During the summer, orioles feed primarily upon insects, including caterpillars, beetles, and grasshoppers. Since many insects defend themselves from potential predators with irritating chemicals, orioles handle their prey carefully. They brush fuzzy caterpillars on branches to remove stinging hairs, and they remove the venomous stinger before swallowing honeybees.

In addition to insects, orioles commonly feed on fruits and nectar. While smaller fruit, such as our native wolfberries, are swallowed whole, large fruit require a different strategy. In lieu of taking a bite out of large fruit, orioles close their sharp bill and insert it into the fruit.

A Bullock’s oriole nest. Wikimedia image.
A Bullock’s oriole nest. Wikimedia image.
They then open their bill to enlarge the hole, and use their tongue, which has a brushy tip, to lap up the fruit juices collecting in the hole.

That brush-tipped tongue is also useful for lapping up the pollen and nectar of flowers. In search of sweet nectar, orioles will visit hummingbird feeders; and you can even purchase oriole feeders, designed to make it easier for orioles to feed. If you decide to put up an oriole feeder, you’ll only need to maintain it for part of the year. By the end of September, the Bullock’s orioles will be winging their way south — flying at night and feeding by day — to reach their Mexican wintering grounds.

This feature is provided by Mesilla Valley Audubon Society, a non-profit conservation and natural history organization which meets August through April. Meetings are free and open to the public. MVAS also hosts regular field trips and other activities. The May 23 field trip will be to Mesilla Park to look for migrating birds. More information at mvaudubon.org.