North American Bird Bander Jul-Sep 2015 Vol. 40 No. 3

Feature Articles

Morphometrics of Worm-eating Warblers in South-Central Indiana: Hatching Year and After Hatching Year Comparison.

Patrick J. Ruhl and John B. Dunning, Jr.

Abstract- We banded 257 Worm-eating Warblers (Helmitheros vermivorum) in south-central Indiana. There was no difference in measurements of size (wing, tail, mass) between hatching year (HY) and after hatching year (AHY) individuals. The distribution of culmen measurements showed that HY birds were significantly smaller than AHY birds. There was no statistical relationship between mass and capture date for AHY birds; average mass of HY birds decreased with capture date.

 

Geographic Variation in the Extent of the Preformative Molt in American Goldfinches.

Erik I. Johnson

Abstract- The described extent of the preformative molt in American Goldfinches (Spinus tristis) varies depending on the reference from only including lesser coverts in some accounts to also including median and many to all greater coverts in other accounts. Resolving these discrepancies and understanding how to accurately age birds is a critical step toward pursuing additional questions about their ecology and evolution. I describe the extent of preformative molts in 150 HY/SY goldfinches caught in Louisiana between December and February over five winters. About 2/3 of individuals replaced all lesser coverts and at least a few median coverts, and 15.3% also replaced one to four inner greater coverts. Differences between my observations and published accounts appear to be explained by latitudinal (north-south) differences with wintering Louisiana birds found replacing fewer wing coverts than northern populations, and regional (east-west) differences with the nominate eastern subspecies (S. t. tristis) replacing fewer wing coverts than the western subspecies (S. t. salicamans). In Louisiana birds, males and females did not differ in the average preformative molt extent; however, I did find a suggestion of a difference in overall body molt intensity in HY/SY males with increased rates from December through February compared to other age/sex classes.