Tree Swallows: Iridescence on the Wing

Swallows of all species are beautiful, graceful birds, swooping acrobatically through the air as they catch insects on the wing.  Tree Swallows (Tachycineta bicolor) are one of our most flashy birds, with their iridescent plumage contrasting with clean white fronts.  In most places, swallows migrate south for the winter, only returning to breed in the summer; but here in California's Great Central Valley, Tree Swallows and similar Violet Green Swallows (Tachycineta thalassina) stick around all year.  Still, they are probably most visible in the warmer months.  I enjoy watching swallows every chance I get, and have been happy to see quite a few Tree Swallows out and about recently. 


Tree Swallows nest in tree cavities, as well as nest boxes.  Because they take so readily to nest boxes, researchers have been able to study the ecology of Tree Swallows in detail.  Like other swallows, Tree Swallows feed primarily on flying insects, which they snatch out of the air with great agility.  Swallows are one of nature's great pest control agents!  They will also consume plant matter, especially in the winter when insects are scarce.  Because of the large amount of insects they consume, Swallows are exposed to high levels of pesticides that bioaccumulate in the ecosystem; these harmful chemicals become concentrated in the bodies of the birds. 


Nests of grass and other soft plant material are placed in cavities, usually excavated by woodpeckers in trees.  Introduced species like the aggressive European Starling compete with our native cavity nesters for suitable nesting sites, and typically succeed in driving out the native species.  Standing dead trees, or snags, provide valuable habitat for Tree Swallows. 

Comments

Post a Comment

You Might Also Like:

Birds of the Desert: Residents & Spring Migrants

Image
Nearly everyone knows the desert as a barren, desolate land of extremes: high heat, low precipitation; little available food and water; prickly, spiny, unfriendly plants growing in a sea of rocks and sand as far as the eye can see.  But for those who stop and look closer, the desert reveals itself as the beautiful, incredible, mesmerizing place it truly is, teeming with unexpected life. Juvenile male Costa's Hummingbird visiting chuparosa blooms next to our campsite in Anza-Borrego Desert State Park. I particularly love the desert in the spring, when the annual wildflowers, cacti, flowering trees and shrubs are all in bloom.  (I've experienced the desert in the searing 120 degree heat of summer, and the rainy, even snowy cold of winter... and spring wins every time!)  Eric and I just returned from a week in the Colorado desert, exploring the imperiled, accidental Salton Sea (more on that coming soon), the vital wetlands of the Sonny Bono Salton Sea National Wildlife Refu
Read more

Great Horned Owl Fledglings

Image
It's spring, and the marshes, grasslands and woodlands of California are brimming with life as young birds of all description hatch, grow and begin to fledge.  I've mentioned before that when I can't get out into a proper patch of wilderness, I enjoy birding at CSU Stanislaus.   This year, there is something particularly exciting on the college campus: a family of Great Horned Owls ( Bubo virginianus ). Great Horned Owls begin breeding very early (or late) in the year, with courtship beginning in the late fall and early winter.  While out for a walk last December, Eric and I heard a pair of Great Horned Owls on campus.  Noting the presence of tall pine trees (potential nesting habitat) and an abundance of prey (gophers and waterfowl), I dared to hope they might choose to stay.  And it turns out, they did! Great Horned Owls lay their eggs as early as January or February in California.  Eggs are incubated by the female for about four weeks, while the male keeps her
Read more

Joshua Tree Woodlands: A Tale of Sloths, Moths and the Trees that Need Them

Image
In 1844, early California explorer John C. Fremont gave a somewhat scathing review of Joshua trees when he wrote, "...their stiff and ungraceful form makes them to the traveler the most repulsive tree in the vegetable kingdom."  Rather unkind, don't you think?  But when Joshua trees were formally described by scientist William Trelease in the 1890's, he noted that Joshua Trees are "the most attractive of all the Yuccas."  I am inclined to agree with this sentiment, and must disagree most heartily with Lieutenant Fremont! I, for one, adore Joshua Trees, with their whimsical shapes and great ecological significance!  If you struggle with plant identification, the iconic Joshua tree, hallmark of the Mojave Desert, is a good place to start.  With densely spiked tufts protruding from the ends of gangly arms stretched towards the heavens, this looks like a plant straight from a Dr. Seuss book.  Native people called these trees “humwichawa,” and used thei
Read more

Exploring New Places: South Carolina's Salt Marshes and Tidal Creeks

Image
Throughout South Carolina's Low Country, winding tendrils of water wend their way through a sea of grass, rising and falling with each new tide.  Low-lying intertidal areas immediately inland from the coast, salt marshes and tidal creeks form the interface between upland forests and urban areas, and brackish estuaries where freshwater and saltwater mix.   Tidal creeks are, to a first-time visitor to the South Carolina coast like myself, absolutely beautiful, mysterious, enthralling places where silvery ribbons of water meander seemingly aimlessly through a vivid green matrix.  They give the impression that there is water everywhere , a foreign concept to someone from arid, drought-stricken Mediterranean California.  And that was my first impression of South Carolina: there was water everywhere I looked!  Water in the ocean, lakes, rivers, creeks and wetlands, water covering the ground, falling from the sky, in the air itself!   Is there any land at all in this veritable wa
Read more

Gardens Gone Native: A Native Plant Garden Tour in the Sacramento Valley

Image
Last Saturday, I spent a very enjoyable day touring 13 of the 21 gardens featured in the 2018 Gardens Gone Native Tour, hosted by the Sacramento Valley chapter of the California Native Plant Society. The centerpiece of this front yard is a young Valley Oak (Quercus lobata).  It is surrounded by plantings of Silver Bush Lupine, Western Redbud, Deer Grass and more, all interlaced with inviting pathways and scattered with annual California Poppies. According to their website , "The purpose of the Gardens Gone Native Tour is to support the mission of the Sacramento Valley Chapter of the California Native Plant Society by raising awareness of the beauty and environmental functions of California's diverse native plants.  Our goal is to provide members of our community with the opportunity to view outstanding examples of native plant gardens, promote the benefits and use of California natives in home and public gardens, and provide information on how to plant and successful
Read more

A Shorebird Primer: Godwits, Curlews, Willets and Whimbrels

Image
For those of us living in the Great Central Valley, autumn is the time to head to the coast.  Of course, there is no bad time to visit California's magnificent coastline.  But as the heat and haze of summer drag on in the Valley, the sea becomes increasingly tantalizing: September and the onset of autumn bring sunny weather and an abundance of migratory seabirds and shorebirds to our coast. A new birder visiting California's Central Coast will undoubtedly be met with a splendid array of very confusing birds.  Among these are small shorebirds like  "peeps" (sandpipers), Sanderlings and various  plovers .  But the larger birds can be just as confusing, until you learn a few distinguishing features.  Four large shorebirds that are commonly seen (and commonly confused) along California's Central Coast are Godwits, Curlews, Willets and Whimbrels. Marbled Godwit (upper left), Whimbrel (upper right), Long-billed Curlew (center front) The distinguishing featu
Read more