Monday, October 29, 2012

For ID Purposes Only (ID Needed)

Sometimes when I am photographing out in the field or in my photoblind I will spot an animal or a bird that is unfamiliar to me.Rather than trying to remember all the details of it I will just shoot a quick documentary image of it. Then I'll to look up later in one of my field guides or try and ID it online. This image is one of those images.I spotted this dark Chickadee coming in to feed with the Chestnut Backed Chickadees at my backyard feeders. It kept landing on the end of a sawn branch before it went to feed. Not a very photogenic perch but at least it would give me some way to ID it. I have checked all of my field guides and numerous places online and so far I have no ID on it. Any thoughts out there ornithologists? Is this a Dark Phase Chestnut Backed Chickadee or something else? Habitat was Mixed Coniferous Forest 2,500 ft. Elev. Coastal Range. Mendocino County, Northern California. God's love and blessings, chris

1 comment:

  1. I passed my question on to number of websites and this is the most definative response that I got.
    Thanks for passing along this photo of this unusual chickadee.

    This bird is melanistic, but not in a usual pattern of melanism where birds are unusually dark.

    Melonocytes (pigment cells in the skin) produce melanin. Melanin is of two types: eumelanin, causing dark color (black and gray) and phaeomelanin, causing rusty red, pale brown and even some dull yellows (bright yellow are carotenoids from the diet). This bird appears to have an excess of phaeomelanin. Not only does it have an excess, it is producing it in regions normally absent in melanin production.

    Melanin is produced by a breakdown of the amino acid tyrosine. An enzyme (tyrosinase) converts tyrosine to an intermediate product called DOPA-quinone. (A true albino lacks tyrosinase—either it cannot be made or a non-functional version is produced.) Further enzymatic action breaks this intermediate down into the two types of melanin. Phaeomelanin is produced in the presence of cysteine, another common amino acid. In some melanocytes, the genes that produce enzymes to make phaeomelanin are turned off and only eumelanin is produced, as seen in the crown of a chickadee. How much is produced will result in black or shades of gray. In other melanocytes, the genes leading to eumelanin are turned off and only those leading to phaeomelanin are active, resulting in the rusty colors, like those on a robin's breast, a Red-tailed Hawks tail, or the chestnut patches on a normal Chestnut-backed Chickadee. Activation of both pathways will result in a blending like that seen on a Wrentit.

    In a normal Chestnut-backed Chickadee, the genes for melanin production (of either type) are not active in the breast and belly. But for unknown reasons, those genes have become activated in this bird. Those melanocytes can make the first conversion from tyrosine to DOPA-quinone, they further convert that to phaeomelanin. All of the bodies cells contain these genes, but it is only in melanocytes where these genes are active and only in select regions. In this mutation, a much larger number of melanocytes have genes in the active condition.

    An interesting condition, resulting in a very stunning bird. Thanks for sharing.

    Dan Gleason