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OCH BLOG

Gearing Up for Fall Migration: Part 3

Updated: Mar 18


Light pollution causes disorientation in birds, increasing their use in energy while flying. Photo by Audubon

We can only imagine the effort involved in migration, especially the medium to long-distance individuals. They must have physical endurance, good health, adequate food resources, be able to avoid predation, handle unpredictable weather, and avoid human-caused obstacles such as communication towers, tall buildings, reflected light from buildings, power lines, wind turbines, and night lights within urban areas. The latter, night lights, can cause all sorts of problems for migratory birds as many birds fly day and night. Artificial lighting and skyglow (light pollution) can cause birds to become disoriented and collide with buildings and windows wrestling in serious injury or death. The night light issue has the greatest impact on birds' energy resources being depleted as birds go off their normal flight path, calling out to others in the flock, or going around these strongly lit areas.

Cliff Swallow nests can be found in clusters built on horizontal overhangs. Photo by Bill Halladay

Our next spotlight species, the Cliff Swallow, Petrochelidon pyrrhonota, is a quick and agile bird that can be seen all around Orange County during breeding season. These small birds can be found anywhere there is a body of water, bridges or overpasses nearby. They, along with some of their closest relatives, build mud nests along vertical walls, under bridges, under residential eaves and more. These speedy flyers come up from Eastern South American, Central America, and Mexico for breeding in California, many other states of the US, and parts of Canada. They have a distinctive white patch of feathers on their forehead that starts to show even before leaving the nest as a fledgling. Cliff Swallows nest in colonies, with colonies reaching up to 3,700 nests in one location. Their diet includes flying insects such as beetles, flies, winged ants, bees, wasps, mayflies, lacewings and some ground dwellers such as grasshoppers and some spiders. They will even eat berries on occasion.


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