Birds Of A Feather, Mexican Bird(S) Of The Month: The Little Birds We Often Miss

By Dennis Taylor

Featured today, are three little birds we often don’t see.  They are small. so you have to be pretty close to even notice them. Usually they prefer to remain out of sight. All three are year-round residents in the San Miguel area. The largest of the trio, the Bewick’s wren is 5-5 ½ inches long and weighs a mere 10 grams, roughly the weight of a couple of nickels. The other two are even smaller, weighing in at 6-7 grams and averaging 3 ½ -4 inches in length.

Bewick’s Wren (Thryomanes bewickii): These hyperactive little birds flit about in search of insects in the foliage. If you happen to have vines or ivy growing in your back yard, or on a wall, you can sometimes get a good view of them there as they search the undersides of leaves for prey.  John James Audubon collected the first recognized specimen in Louisiana in 1821, and named if after his friend, Thomas Bewick, a British engraver. Bewick’s wrens are easy to identify by their bold, luminous white eyebrow. While most wrens hold their tails straight up, the Bewick’s wags its barred tail side-to-side, almost like a dog.  Although most birds learn their songs from their fathers, young males learn their songs from neighboring territorial males rather than their fathers.  A single male may have 20 different versions of his song. These vocalizations are used to protect his territory.

Its range is now restricted to the Mexican highlands north of México City, and along the western coast from Baja California to the Canadian border. Their decline in the eastern United States coincides with the expansion of the Northern House wren which frequently removes Bewick’s eggs from their nests.

Blue-gray Gnatcatcher (Polioptila caerulea): A tiny, bluish-gray bird with a grayish-white breast, it has a white eye-ring and long black tail with outer white feathers on each side. The Blue-gray specializes in aerial acrobatics to capture insects.  Hopping about in trees and shrubs, they constantly flick their long, white-edged tails from side to side.  This scares insects out of hiding, and they snatch them mid-air as they attempt to fly away.

Their nests are impressive works of art.  They use spiderwebs and caterpillar silk to bind the nest together, then they decorate the outside of the nest with bits of lichen for camouflage.  They use so much spider silk, their nests are a bit stretchy.  As their chicks grow larger, the nest actually expands to accommodate them.  They are necessarily prolific, building up to seven nests in a breeding season, because predation, nest parasitism and mite infestations frequently lead to brood failure.  In spite of their small size, they are incredibly territorial.

Verdin (Auriparus flaviceps):  Verdins have a grayish body and yellow head accented by a small, triangular red shoulder patch.  This tiny denizen of the desert scrublands is primarily an insectivore. However, they are quite happy to supplement their diet with fruits, and even nectar which they sometimes obtain by piercing the base of flowers. A bit of an “oddball”, they are the only representative of the family Remizidae found in the Americas. The Verdin actually builds two types of nests; one for laying eggs, and the other for roosting.  While both are globe shaped, their blueprints differ significantly based on purpose. The breeding nest is built as a fortress for the chicks, protecting them from both predators and desert heat.

It is larger, 6 to 10 inches in diameter, and features a thick, heavy lining of grass and feathers on the inside with thorny twigs on the outside. The thick roof acts as a “thermal shield” blocking direct solar radiation which would otherwise cook the eggs.

The entrance is usually oriented toward prevailing winds of late spring and summer to prevent the interior from overheating.  Roosting nests are much smaller, usually built by a single bird in about 4 days, and even more heavily insulated than breeding nests.  It accommodates just one bird snugly, helping to retain the birds’ trapped body heat and reducing energy needs to stay warm by as much as 50%.  Sadly, the Verdin is on the decline throughout its range.

While these birds are tiny, their "ecological footprint" is huge. The Verdin pollinates desert plants, the Blue-Gray keeps fly populations in check, and the Bewick’s is a master of pest control in the undergrowth.