• At 9:35 AM four bags with bright pink clips (at Powdermill this indicates large, band size 1A or above, and/or biting birds) were lined up on our shelf, next in line for processing.   The first three produced the expected Rose-breasted Grosbeaks, two new and one recapture.  The fourth, however, was the bird pictured above, which, from the above angle, could easily be mistaken for just another female Rose-breasted Grosbeak.

.
Different views of the bird, however, reveal some very different plumage traits that quickly caught our attention, because they are not seen in adult female Rose-breasted Grosbeaks.  The only question at first was whether this bird was another Rose-breasted X Black-headed hybrid (one of these was banded in May 2003), or Powdermill's first ever Black-headed Grosbeak.  Our conclusion--the latter!!
.
The key field marks: very fine breast streaking, buffy breast and flanks, posterior supercilium (line above the eye) blending buffy with the nape, and buffy/mustard yellow underwing.

• The photos below compare the adult female Black-headed Grosbeak (left and top bird) and an immature female Rose-breasted Grosbeak (right and bottom bird).  The buffy posterior supercilium and nape is highlighted in the middle photo.  In addition to the difference between the breast streaking and buffiness on the breast, notice also the darker yellow underwing coverts in the top photo, the more richly colored upperparts in the middle photo, and the buffier undertail coverts of the Black-headed Grosbeak in the bottom photo.

• After the photo shoot, adult female #1841-20547 Black-headed Grosbeak, was promptly released.  Normal banding resumed and a lunch celebration commenced after closing of nets at noon!

• For the record, the full measurements of the BHGR were: wing length, 104.5mm (would be quite a large female Rose-breasted Grosbeak); fat, 1; body mass, 41.9g.  She had completed her prebasic molt of wing and tail feathers, but still had scattered molting body feathers.

• The day after banding the BHGR, we banded a few adult female Rose-breasted Grosbeaks, which provided a more appropriate comparison.  Adult female RBGR tend to have a buffier median crown stripe and buffier underparts than HY females, but their breast and side streaking still is very noticeably wider and more extensive than the BHGR.

---

< Home >

Last Updated on 09/24/04
By Adrienne J. Leppold