Highway Cleanup Birds
by Ro Wauer
On a trip last week to the Big Bend Country, I was once again impressed with the common ravens that each morning patrol the highways searching for road kills from the previous night. Years ago when living in the Big Bend, I counted ravens along the highways when driving from the park to Alpine or Marathon during the early mornings. I eventually estimated that a pair of these large, all-black scavengers would occur every five to ten miles. They were well-spaced along the highways, apparently in distinct territories, to claim any available dead animals early each morning. They were flying at dawn before any of the other daytime predators, such as vultures, were up and around.
Turkey vultures clearly are the most numerous roadside scavengers in most of Texas, while black vultures are just as numerous in the southeastern half of the state. But vulture are lazy birds, usually not on the wing until after sunup, and they oftentimes fly over large areas, with little regard for the roadways, at least until they discover a two- to three-day old carcass. It is the early decaying process that most attracts vultures that are able to find food by its aroma. Fresh kills are often ignored. In fact, during my college years, I initiated a science project to test this theory. I placed different aged carcasses, each covered with newspaper so they could not be seen from the air, out in a field for several days in a row. Turkey vultures would fly to and feed on the two- to three-day carcasses only, leaving the less putrefied carcasses alone.
Although common ravens are clearly the most numerous highway birds in West Texas, crested caracaras perform the same cleanup duties in South Texas. In our part of Texas, it is not unusual to see a pair of caracaras searching the highways early each morning. They fly along the highway in what seems like daily routines, perhaps one of the reasons caracaras seem so numerous. And every now and then, another avian predator can be found taking advantage of what is left from the ravens and/or caracaras leftovers. Crows frequently take advantage of an easy meal.
Perhaps it is the drought conditions that currently exist throughout much of Texas this year, for I have noticed more other bird species feeding on the leftovers than usual. Wintering red-tailed hawks were seen feeding on carcasses on a couple occasions on my recent trip. And on one occasion I found a loggerhead shrike sitting on a dead cottontail taking out chunks of meat. In spite of their small size, at least in comparison with ravens, vultures, hawks, and even crows, shrikes are tough little birds, one of our few predatory songbirds.
Another hawk seen just north of Big Bend National Park this year was the Harris's hawk, a desert species that just barely reaches the Gulf Coast. A pair of these colorful hawks was perched on adjacent fenceposts, apparently feeding on a road kill that they had discovered or, perhaps, had taken away from a raven. Harris's hawks are fascinating birds for several reasons. They are gregarious birds that hunt in family groups, usually a pair of adults and several offspring, easier to wear down a jackrabbit or cottontail. And the previous year's young are "helpers," in that they often help the parents build or rebuild last year's nest and even help feed the new nestlings.
On one trip to the park a few years ago I encountered a Harris's hawk flying alongside of a badger. I stopped my vehicle some distance away and watched through binoculars as the badger wandered along, turning over cowpies in search of insects and whatever else might be hiding there. After each pass, as the badger proceeded on to the next cowpie, the Harris's hawk would fly down and examine the overturned cowpie, taking whatever the badger had left behind. This behavior continued across the field to where they disappeared behind some low shrubs. I couldn't help but wonder if that same kind of behavior was taking place this year when making a living is so difficult.