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Forrest M. Mims III
In the United States songbirds, waterfowl and monarch butterflies will soon begin their fall migration.
In early August an early wave of monarchs flew through our place in South Texas. I thought this might signal an early winter, but Dr. Chip Taylor of the Monarch Watch project at the University of Kansas advised me that the early monarchs are probably part of the pre-migration that precedes the main migration. A single monarch was seen while this column was being prepared, so maybe the main migration is on the way.
Among the most interesting songbirds in the fall migration will be the loggerhead shrike (Lanius ludovicianus). From a distance the shrike can be confused with the mockingbird (Mimus gilvus). Look closely, and you will see obvious differences.
Figure 1. This loggerhead shrike is shown with a assortment of typical shrike meals (a snake and two cicadas) impaled on barbed wire. Photograph by Forrest M. Mims III.
The shrike is stockier in appearance than the mockingbird and its wings are shorter. The clincher is its head, which is gray on top with a black band across its eyes that is reminiscent of the face of a raccoon or perhaps the Lone Ranger. Bandit comes to mind, but I don’t want to be accused of libeling an entire species.
The shrike is very businesslike about flying. It tends to fly in a straight line propelled by very fast wing beats.
In many years of trying, I’ve managed to get only one photograph of a nearby shrike. The bird landed on a fence near my office window, and I photographed it through the glass almost straight on. Its gray cap, black mask and beak and white breast are clearly visible.
Songbirds generally eat seeds or small insects. But the diet of the shrike is more like that of falcons and hawks, and so is its bill.
In an article for The Nature Writers of Texas web site, Ro Wauer describes how the bill of the shrike features a sharp projection on the upper beak that fits in an indentation in the lower beak. This allows the shrike to securely grasp and kill its prey.
Shrikes are meat eaters, and they often catch large insects and small animals that are much too large for them to swallow. So they impale their prey on sharp yucca leaves, thorns or barbed wire. This is why they are commonly called butcher birds.
At our country place shrikes seem to prefer barbed wire fences for storing their meals. But that may be because their prey are so obvious when stuck on a exposed barb. There may be as many or more prey impaled on cactus and mesquite thorns that are much less obvious than fences.
The variety of meals selected by shrikes is impressive. At our place, the most common prey are cicadas and large grasshoppers.
The shrikes at our son’s place in Victoria are more ambitious, for the fences there have been decorated with lizards, small snakes and even a mouse. Shrikes can reportedly kill and eat birds larger than themselves, but I’ve not seen evidence of this hanging on a fence
"World of Science" columns
are selected and sometimes revised from columns published
in the San Antonio Express-News or the Seguin
Gazette-Enterprise. The columns are intended for a general
audience. Forrest M. Mims III and his science are featured
online at www.forrestmims.org
and www.sunandsky.org
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