New Westward Breeding Records for Eastern Towhees in Central Nebraska

Authors

William C. Scharf

Date of this Version

3-2005

Citation

“New Westward Breeding Records for Eastern Towhees in Central Nebraska” from Nebraska Bird Review (March 2005) 73(1).

Comments

Copyright 2005 Nebraska Ornithologists’ Union. Used by permission.

Abstract

The current breeding range of Eastern Towhees (Pipilo erythrophthalmus) in Nebraska is described as westward to a line from Cedar Co through Platte, Hall, and Harlan Cos (NBR 64: 124, Sharpe et al. 2001). Frequent recent sightings of Eastern Towhees during the breeding season have been made from more westward locations. A few reports are from Lincoln Co., 5 June 2004 by TJ Walker (NBR 72: 91), and Dawson Co., 13 May 2004 by Laurel Badura (NBR 72: 55). In contrast to the capture data presented here, none of the sightings is corroborated with breeding condition data such as cloacal protuberance or brood patch nor are nests located. Further recent sightings (Silcock in press NBR: 73) indicate the probability of Spotted Towhee genes in the eastern-most counties of Nebraska through intermediate songs and plumage. There are no other known capture studies that have data of the type presented here from the central Platte River valley.

Sibley and West (1959), working from museum specimens, indicated genetic influences of Eastern Towhees in central Nebraska with their hybrid index based on a scale from 0 to 7 for combined sexes, with 0 being pure Eastern Towhee phenotypes and with scores greater than 0 influenced by Spotted Towhee, P. maculatus, genes. In an east-west gradient along the Platte River, Elm Creek had a hybrid index of 1.9, Gothenburg 2.0, and Sutherland 2.2. This is contrasted with much higher scores of 3.5 and 3.8 for birds collected at more northerly locations on the Niobrara River and at Chadron respectively. The values for Blair and Omaha indicate nearly pure populations of Eastern Towhees with a 0.14 score. Scharf and Kren in Brown et al. (1996) recorded 33 mostly Easterns and 29 mostly Spotteds out of 62 hybrid birds banded at Lake Ogallala.