Scheduled post: Yellow-breasted Grosbeak

Abnormal Rose-breasted Grosbeak

We caught this bird during our normal MAPS operations on our previous visit to Maplewood Bog. No, it’s not a new species – it’s a Rose-breasted Grosbeak with some plumage abnormalities. We weren’t sure exactly what was going on here when we caught it. When we got home, I did some searching online (ah, the miracle of the internet) and turned up this discussion on the WhatBird Forums. In it they quote an article written by Julie Craves (Coffee & Conservation) where she discusses a similar bird.

The yellow breast (and underwing coverts), it turns out, are the result of a condition called xanthochroism. Just like albinism is a lack of pigment, and melanism is an excess of pigment, xanthochroism is an abundance of yellow pigment. It may be caused by certain abnormal items in the diet or dietary deficiencies, or may be genetic. The yellow may either be present in excess, or it may replace another colour (usually red, which is often itself controlled by diet).

Abnormal Rose-breasted Grosbeak

This individual was an older bird, at least three years old (“After-Second Year” in banding lingo) based on certain plumage characteristics, but given the extent of white at the base of his primaries, he may be much older than that. Oftentimes, as a bird ages its markings grow in size or extent and can be a rough gauge of age. It’s not a perfect science and there’s always exceptions (who knows if it’s linked to his yellow breast), but this guy may have seen quite a few summers – I can’t recall ever seeing a grosbeak with such an extent of white on his wings.

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10 responses to “Scheduled post: Yellow-breasted Grosbeak

  1. Hi
    I love your blog !!!

  2. Wow, love your blog! I am scouting the blogs at NBN.

  3. Love the weird grosbeak! It’s not too uncommon for adult male House Finches to show yellow pigmentation instead of the red, and I think there’s been at least one yellow Northern Cardinal documented…

  4. great blog and post- thanks for the info

  5. Pingback: Ten for ‘10 « the Marvelous in nature

  6. Thanks for the information. Couldn’t image what bird it was. We just saw one in our yard in Rocky Hill, CT.

  7. Leslie Ritter-Jenkins

    I saw two male rose breasted grosbeaks at my feeder today and one male with the yellow/golden coloring and one female. I did a double take on the yellow markings and was happy to find this blog. I am curious where the other males with yellow have been sited. 5-10-13 La Grange Park, IL, 20 west of Chicago.

  8. We had a beautiful yellow breasted grosbeak sharing our feeder today with several rose breasted grosbeaks. We are in Woodbury, 10 miles East of St. Paul,MN.

  9. Good morning. Your post came up when I was researching the grosbeak with a yellow patch. I too have seen the male like you posted but also a female. I’ve photographed the male but not the female. I saw them in Eau Claire County, Wisconsin.

  10. We have a beautiful young yellow breasted grosbeak at our feeder today, along with several rose breasted fledglings and their parents. Wow! Gorgeous! We are in the southwestern part of Wisconsin, about 3 miles east of Governor Dodge State Park.

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