What to watch for in September: Migrating Swallows
Here’s the Central Texas bird forecast for the month, courtesy of Travis Audubon. Learn more about Central Texas birds and bird-related events for all ages at travisaudubon.org or by calling 512-300-BIRD. Follow us at www.facebook.com/travisaudubon
Swallows are small to medium-sized songbirds that mainly eat flying insects. In central Texas we have seven regularly expected species. Five species breed in the Austin area. They are joined in the fall months by their northern relatives heading south for the winter. All are heeding nature’s call to leave before the insect prey they depend on are depleted. (Swallows are at risk for starvation and hypothermia in the event of a severe early cold front.)
Most Purple Martins leave the Austin area by the end of August. Most Cave and the similar Cliff Swallow are passing though now, and will be thin on the ground in October. Ditto for the Northern Rough-winged Swallow. Barn Swallows migrate through in August, September and early October with stragglers in November. The sixth and seventh species, Tree and Bank Swallows, don’t typically breed in Austin, although both are expected breeders in central Texas. Tree Swallows appear in the migration window of September and October and Bank Swallows in August and September, with most observations of Bank Swallows in September.
Bank Swallow – the smallest North American Swallow
The Bank Swallow is tiny, at 5.25 inches in length. It’s a study in shades of brown, with a brown head, back, wings and tail. These muted colors contrast with clean white underparts and a white throat that highlight the brown breastband, a diagnostic feature. Sometimes the breastband has a ventral stripe that goes down to its belly, too. Its wingbeats are characterized as quick and fluttery. The Bank Swallow often makes a distinctive repetitious electric buzzy “chirr” sound.
While Bank Swallows do breed in a few locations in south and central Texas, they are mostly birds of the northern U.S., Canada and Alaska. Bank Swallows are colonial nesters, with documented colonies in the U.S. of less than 10 to 2,000 active nests. They nest in the varied types of friable soils of river and lakeshore banks, bluffs and cliffs. Amazingly, they do this by tunneling into the banks using their bills, feet and wings to excavate a burrow about 20 to 39 inches in length. After the burrows are complete the mated pairs build nests at the back and the females start their broods. Deeper nest burrows are associated with higher nest success. The most sought-after nest sites are situated just under the top of the banks. These are safer from collapse and predators like snakes, than those at the edge of the colony or lower down the bank.
Fun Facts about Bank Swallows
They are a gregarious songbird species that can be found widely distributed around the world on all the continents except Australia and Antarctica.
Bank Swallows have adapted to human-created sites like gravel and sandpits in some parts of their range. Fortunately many commercial operations delay mining nest sites when the birds are present.
Many of its breeding sites are ephemeral due to the erodible nature of the river or lakeside habitat they choose, prone to natural events like flooding and storms.
Shimmering Tree Swallows
The slightly larger Tree Swallow can be mistaken for a Bank. Both have white underparts, with Trees maybe a little brighter white. However, instead of being brown, the adult male Tree Swallow has an iridescent blue-green back and head, visible in good light. Adult females can have variable amounts of iridescence, but they also may look very black compared to the brown tones of the Bank. When Tree Swallows are flying the small white crescents on the sides of their rumps may be visible. Keep in mind that young Tree Swallows have a dusky-looking breastband compared to the more defined breastband of the Bank.
Tree Swallows are an expected breeder within a 60-mile radius of the Austin area. They are not colonial nesters like Bank Swallows. Nesting Tree Swallows rely on tree cavities, but have adapted to nestboxes. They use white feathers of many species to line their nests, and have often been observed dropping feathers and recatching them in what looks like play behavior.
Flocks of Tree Swallows gather by the thousands during migration. It’s a thrill to be out birding and stumble across a flock of this size.
Swallow Watching
Swallows can be challenging to identify since they like to fly back and forth through insect swarms, at dizzying speeds. The great thing about Fall is there are lots of swallows about, and they like to rest on wires or on top of bushes. When they do, you can get better looks, grab a picture or two, and consult your field guide to piece together an ID. The Cornell Lab of Ornithology’s free Merlin app can help with both sound and photo ID.
What are some features to look for, if you are honing your bird watching skills? Depending on the species a swallow’s tail can be long, forked, squared off, short, or notched. Swallow wings can be slender, rounded or broad-winged. Flight styles can vary from butterfly-like to smooth. Swallows incorporate shades of earth tones- brown, buff, cinnamon, rust, along with blue, black and white. A fun way to study them is to visit a spot where swallows fly below you – Roy Guerrero’s Cliff Overlook just west of the playground at 400 Grove Blvd. is one such spot. Don’t worry about the swallows’ identification. Instead just enjoy the birds and see if you can distinguish color, tail shape, rump color, wing shape and flight pattern. Sometimes it’s easier to track the birds with your eyes rather than binoculars. Try to stay focused on one bird at a time. Foraging flocks are often a mix of species. Scan the wires for roosting birds. Learn a tip for each species. For example, Bank Swallows are noticeably smaller than other species, obvious on roosting birds. Adult Cliff Swallows have a white patch on their foreheads. Juvenile Barn Swallows’ tails are not as long as the adults’.
Hornsby Bend is the premier swallow watching spot in Austin, as it has wires and shrubs for resting birds, lots of flying insects, water and expanses of open space over the ponds for flying. Early morning and towards evening are the most productive times for swallows in flight. Mid-day they will probably be loafing. Check out the monthly Hornsby Bend Bird Observatory free field trip on September 19 that will orient you to this birding hotspot.
Upcoming Travis Audubon Events
It’s September and we like to think it will be cooler. The birds are outside regardless of the temperature, and Travis Audubon offers many reasons to get outside. Check out the September calendar and register for a fun field trip. Barton Springs, Commons Ford Ranch, Hornsby Bend, Reimers Ranch, the Lady Bird Johnson Wildflower Center and Zilker Botanical Gardens are just some of the field trip options this month.
Not a morning person? Chimney Swifts are getting ready to go to South America for the winter. They are staging at roosts all over town, and Travis Audubon will highlight one, with a Swift Night Out at the JJ Pickle Research Campus, on Sept. 11. Watch the swifts swoop, swirl and then plummet into the roost site as the sun goes down. No registration required. Travis Audubon also has several fee-based classes available in September, too, from raptors to beginning birding to birding by ear.
Compiled by Jane Tillman, Travis Audubon Volunteer
Resources: All About Birds, Birds of the World, the Travis Audubon Seasonal Distribution Checklist, The Texas Breeding Bird Atlas, The Sibley Guide to Birds
