Cliff Swallows: Aerial Acrobats & Adept Architects

Spring is in full swing here in California's Great Central Valley, and for a naturalist, that means blue skies and warm weather, blooming flowers and budding trees, butterflies and baby animals, and, of course, birds!  Spring brings a whole new assemblage of bird species to the Valley: colorful, subtropical birds that spend winters in Central and South America.  A few of these birds include Western Tanagers and Black-headed Grosbeaks, both of which nest and spend their summers in the conifer forests of the Sierra Nevada; riparian species such as Bullock's and Hooded Orioles; brilliant blue Lazuli Buntings and a host of warbler species.
 
Another group of birds that have returned are among my favorite birds to watch: the swallows.  Some species, such as the Tree Swallow and Violet-green Swallow remain in the Central Valley through the winter.  (Other populations of these swallows are migratory.  But as long as a food supply - namely insects - is present, sticking around through the winter gives these cavity nesters a chance to snag a nest site early, before they're all taken!)  But Barn Swallows, Northern Rough-winged Swallows, Bank Swallows and Cliff Swallows spend winters in warmer environments where the insects supply is assured.   
 
An adult Cliff Swallow peers out from a nest
 
Every spring, owing to the age old mystery of migratory instinct, Cliff Swallows (Petrochelidon pyrrhonota) return to their temperate breeding grounds.  (Famously, they are said to return to Mission San Juan Capistrano every year on March 19th.)  The first individuals arrive in the Great Central Valley in February and March, and by April they are busily constructing mud nests underneath building eaves and bridges all across the Central Valley!  A sure sign of spring indeed!
 
It's a happy day when I spot my "FOS" Cliff Swallow, since that means spring is imminent!  (If you're curious, "FOS" is birding code for "First of Season," the first bird of that species you've seen that season.) 
 
Cliff Swallow nests under construction beneath a bridge over a pond
 
And of course, I intended to write this sometime near the end of February when I saw this season's first Cliff Swallow... but since that didn't happen, I'm doing it now!  But this is an appropriate time as well, since right now there is a flurry of winged activity around any Cliff Swallow nesting site!
 
Construction is a busy time for the swallows!
 
Cliff Swallows are found in open habitats, from farmland and grassland to rivers and lakes in arid landscapes.  They build their nests in the shelter of an overhang on a vertical surface: cliffs and river banks are favored in wild habitats, but with increasing frequency they nest alongside humans.  Often undisturbed spots beneath building eaves and bridges provide ideal nesting habitat.  Nests are built in tightly-packed colonies of hundreds, even thousands of individual birds (the largest colonies appear to be in Nebraska, with thousands of nests!) 
 
Gourd-shaped nests tucked safely beneath sheltering eaves
 
Cliff Swallows require a nearby source of freshwater, as they construct their nests entirely of mud collected in their mouths.  Though closer is better (hence the appeal of bridges for nesting site) these intrepid little architects will fly up to a few miles to gather mud in their bills from lakesides, stream banks or puddles.  One nest requires over 1,000 mouthfuls of mud to build!
 
Cliff Swallows flock to puddles, lakesides and stream banks to collect mouthfuls of mud for nest construction
 
Each nest measures about 8 inches by 6 inches and is roughly gourd-shaped, with a small 2-inch opening at the top or side.  Males and females work together to build their nest, often "renovating" an existing nest from the previous year.  The inside of each nest is lined very sparsely with grass and feathers.
 
 
Water is also a necessary component of suitable habitat because it attracts insects, the primary food source of all swallows.  It is a treat to find yourself in the midst of a foraging flock of swallows, the small birds wheeling and turning and diving all around you in their acrobatic hunt for winged insect prey.  They feed almost entirely on the wing, skimming low over bodies of water or flying high above the ground to nab insects; generally only when bad weather prevents insects from flying will they feed on the ground.
 
Young Cliff Swallows in their cozy nest

Cliff Swallow populations seem to be stable over much of their range; it is promising to see this species adapting well to its human-altered environment!  Introduced from Europe and highly invasive, House Sparrows probably pose the biggest concern to Cliff Swallows, as these feisty little birds spread rapidly and appropriate swallow nests for their own use.


As you're out and about this spring and notice little birds fluttering about near bridges and eaves, take a few minutes to admire their handiwork and watch the aerial acrobatics of these enthralling creatures!

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 ...
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....
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 Cu...
Read more

All The Ducks!

Image
On a recent birding trip to Merced National Wildlife Refuge, I tallied up a list of sixteen different species of ducks.  Only a few more species, around twenty in total, are expected in the Central Valley of California's freshwater marshes during the winter, so I consider that to be an excellent day for ducks! North American ducks are broadly separated into two categories, largely based on their methods of foraging for food.   Dabbling ducks , also known as "puddle ducks," tend to frequent shallow water, where they are commonly seen tipping bottoms-up to feed on plant matter and invertebrates in the water and on the muddy bottom.  They are most at home in water, but walk easily on land as well, as their legs are positioned near the center of their bodies.  The wings of dabbling ducks are relatively large, which allows them to take off from the surface of the water, straight up into their air.  Dabbling ducks almost all nest on the ground, near water....
Read more

Birding in Adverse Weather Conditions: Wind and Rain

Image
Though I often extol the virtues and merits of winter in the Central Valley , especially when it comes to birding, the whole truth is that we experience "bad" weather also, just like anywhere else.  But even when the winter weather rolls in, the birds are still out there!  And sometimes, despite our best planning efforts, a birding day happens to coincide with crummy weather.   In that case, what's a birder to do?  Usually, we go birding anyway!   Birders far more intrepid than I regularly brave the ice and snow of northern winters to see their favorite birds, so perhaps you should look to them for real tips on winter birding!  For those of us in the valleys of California, the worst weather we see - wind and rain - is really comparatively mild.  Birding on an extremely windy day! I don't know of anyone who actually likes birding in the rain.  But I would argue that birding in the wind is just as aggravating as trying to bird in the rai...
Read more

Winter Gulls: The Great I.D. Challenge

Image
Gulls are a fun challenge for birders, from beginners to experts.  A few things make gulls an interesting study: they are large and conspicuous in their open habitats, so they are easy to see, easy to put a scope on, and easy to watch and study for long periods of time.  Furthermore, gulls are almost always identifiable as gulls; none of this confusing warbler/vireo/kinglet nonsense! And yet, gulls are almost impossibly difficult!  (Though perhaps not nearly as difficult as Empidonax flycatchers!) An intimidating scene to many a birder: a mixed flock of gulls.  I see five different species of gull here. Oh, and one American Coot in the background. One of the reasons they are so complicated is most gull species take two or three years to achieve adult plumage, and go through multiple molts in a year.  So, you may be looking at three or four gulls together that look like four completely different species, when they are actually just different ages (...
Read more