July 5. 2008

THOSE CLEVER SWALLOWS

Rex Burress

The Oroville High School has done some extensive rebuilding, and one elaborate unit was an Industrial Arts building. They included long, outreaching eves, with the supporting rafters also adding to the shade in that summer-hot California country.

There are certain birds in our communities just watching for an opportunity to use manmade structures, and the Cliff Swallow, alias Petrochelidon pyrrhonota, is one of the most opportunistic. About 30 pairs of the handsome, graceful aerial artists, must have thought that art building had been built for them, because they plastered their mud, jug-shaped nests under that sheltered overhang!

Cliff Swallows are more prone to build nests under bridges, but they readily adapt to any structure that provides a protecting roof and strong support. Their presence is desirable since they eat a lot of insects including mosquitoes, but sometimes there is objection to the mud droppings, especially around a new school building, and their nests are often hosed down. This happened at the Sonoma State University one year, and a gigantic student protest changed the policy. Now officials wait until they have finished raising their young before cleaning up.

It is quite remarkable the way that butterfly-like bird settles at a mud puddle, much like butterflies seeking to sip a drink, cram their mouth full of mud, and then go flashing back to a building site. You wonder how many trips they must make in order to construct that elaborate jug-shaped nest with the round entrance hole. Getting it all to stick together is another slick feat. Jays have been known to attack the thin-walled mud nest, break through and steal eggs or babes. Nothing is sacred in the animal-eat-animal world!

Most Butte County bridges have swarms of cliff swallows in the summer–even the Bidwell Bar relic bridge! They do what they do and they know what to do...by some power.

It is interesting that each of the seven western America species of swallow has its own idea of what constitutes a nesting site. The Cliff Swallow and Barn Swallow take advantage of manmade structures, while the Tree, Violet-green, Northern Rough Winged, Bank, and Cave Swallows seek out natural homes, especially in tree crevices, cliff cracks, steep banks, and caves. The Cave Swallow also builds a mud half-bowl nest somewhat like the Barn Swallow.

Despite their nesting variety, they all have a similar flying style, gracefully dipping and sailing in the sky, catching insects on the wing. They do it so quickly you can hardly see them open their mouth. On colder days, they fly low to the water to pluck downed insects.

While the Purple Martin is included in the swallow grouping, the high-flying swifts are in a group of their own, more related to hummingbirds in structure, even though they act much like swallows. Their flight is more stiffish with short quick bursts.

At Oroville, White-throated Swifts return each year at Table Mountain Bridge near the Feather River Nature Center, often resting on the bridge beams after their long flight. They seem to be a-wing most of the time, and some nest in the bridge drain pipes, shooting into that round slot at full speed, all the time chattering in a distinct call.

Go swallow watching if you want to see some reliable bird observations in the summer! They will fly south in the fall in flowing flocks to follow the call of insect abundance, so see them in the summer season!