From: James V. Remsen
To: LABIRD-L mail list
Subject: Rose-breasted vs. Black-headed grosbeaks in fall
Date: 11 October 2016

LABIRD: several times each fall, I am sent photos of possible “Black-headed” Grosbeaks because their breasts are so richly tawny. This is understandable because field guides do a poor job in illustrating male plumages in fall. For example, the Sibley guide soes not show an adult male in fall, and the HY male is drawn incorrectly. Both plumages are rich tawny below, just like Black-headed Grosbeak, but more heavily streaked.

So, here are some specimen photos that may help:

1. HY (first fall) males:

https://www.flickr.com/photos/126193733@N06/30185639521/in/datetaken-public/
https://www.flickr.com/photos/126193733@N06/29974438730/in/datetaken-public/

Notice how tawny they are below, although the degree is variable. In fact, note the variation in general, and from this small sample, you can imagine that the true range of variation is much higher. However, they all have one thing in common — they all have at least a trace of ROSE in the breast (illustrated without rose in the Sibley guide). The rose color ranges from obvious to barely detectable, but in these and all others I examined today in the collection, the rose was present. Note also the varying amounts of black in the upper wing coverts. I thought at first this might be HY vs. SY (second-yr) birds but all the specimens here have only partly ossified skulls (the newer, whiter labels) or all brown rectrices.

2. AHY (at least 1 year old) males. This plumage is not illustrated in Sibley or Peterson (and my Nat. Geo guide is missing):

https://www.flickr.com/photos/126193733@N06/29640374334/in/datetaken-public/
https://www.flickr.com/photos/126193733@N06/29974354410/in/datetaken-public/

All of these have more extensive red below and thus not confusable with BHGR. They have large white spots in the black tails (compare to the obscure spots on brown tails of HY birds). They are highly variable in ventral tawniness. The lateral view shows their all-black wings except for the white spots. The markings on the flanks tend to be more like spots than the streaks of HY birds.

================= Dr. J. V. Remsen Prof. of Natural Science and Curator of Birds Museum of Natural Science/Dept. Biological Sciences LSU, Baton Rouge, LA 70803 najamesLSU.edu

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Dr. J. V. Remsen
Prof. of Natural Science and Curator of Birds
Museum of Natural Science/Dept. Biological Sciences
LSU, Baton Rouge, LA 70803
najamesLSU.edu