Prairie Ridge Ecostation

Aging Loggerhead Shrikes

By John Gerwin, Curator of Birds

A Loggerhead Shrike (Lanius ludovicianus) was captured and banded during this October during our latest bird banding session at Prairie Ridge. A species of special concern, shrikes have largely disappeared from densely populated urban areas in North Carolina.

For the past few years, 1-2 birds have been found at Prairie Ridge during the non-breeding season. In addition to the recent October bird, in March of 2007 a shrike was captured and banded.

This recent capture is a "young" bird— a bird that was hatched and raised this year. We know this by the pale gray barring on the breast, and by the molt pattern we see. When young songbirds (a group in which shrikes are classified) leave the nest, they are wearing "juvenile" feathers. The body feathers (but not the wing/tail feathers) are shed and regrown (molted) usually within a month.

A young Loggerhead Shrike being banded at Prairie Ridge        These gray bars indicate that this bird is less than a year old        Tail feathers molt in a pattern starting with the middle feathers, the shorter feathers have not completely grown back yet.

Wing feathers are known by various names, depending upon their origin and function. The primary feathers arise from the hand bones and are the outermost fingers. The secondary feathers arise from the ulna bone, and these are the trailing feathers. Coverts are feathers that, as implied by the name, cover other feathers, and on the wing, the coverts cover the bases of the primary and secondary feathers. Color, shape, and wear can all aid in the determination of the age of a bird, whether it is a very young bird or not.

             This molting primary is half complete         The dark coverts have worn edges, another indication of a young bird

The outermost tail feather pictured is the "old", original feather, and will likely be replaced as the season progresses. The outermost primary wing feather has nearly finished growing in. It has been noted that migrant shrikes usually finish their molting by the end of September, and that a bird still molting in late October is likely one from the resident, non-migratory (breeding) population. Thus, our October bird was likely "born and raised" in North Carolina.

Find out more about the natural happenings at Prairie Ridge at our What Time Is It In Nature Archive.