Golden-crowned sparrow???

[Christian Dionne]

This one was alone with a bunch of white-crowned sparrows, pictures taken in San Francisco, CA last monday...
It looks a little washed-out but it's not the picture, the actual bird was this pale.






Thanks!

[John Chardine]

Christian- This is a very interesting image! In my opinion it shows an "isabelline" variant of a sparrow. Isabelline refers to a situation where the darker pigmented feathers are faded to a light beige colour. As to what sparrow it is I'll let others comment first! Thanks for posting.

http://en.wikipedia.org/wiki/Isabelline_(animal_colour)

[Christian Dionne]

Thank you John!
Isabellinism is a new one for me, I knew about leucism already though.

Thank you for your answer.

[Chris Sloan]

Looks to me like a leucistic White-crown.

[John Chardine]

Looks to me like a leucistic White-crown.

Chris- Leucism produces white body parts, e.g., a crow with white wings, an all-white puffin with a dark eye. Isabellinism is a gradient of this where the pigmented body parts face to beige ("isabelline" colour), not white.

Thanks for the ID. So we have a White-crowned Sparrow on the block. Comments?

[Chris Sloan]

Chris- Leucism produces white body parts, e.g., a crow with white wings, an all-white puffin with a dark eye. Isabellinism is a gradient of this where the pigmented body parts face to beige ("isabelline" colour), not white.

Thanks for the ID. So we have a White-crowned Sparrow on the block. Comments?

Isabellinism is a form of leucism. Leucism simply refers to any reduction of the ability to produce pigment pigment.

[Christian Dionne]

Looks to me like a leucistic White-crown.

I was thinking golden-crowned because of the yellow spot on the head and the bill seems dark for a white-crown???

From what I understand, this sparrow IS leucistic and if I want to be more specific I could say Isabelline, right?

Thanks!

[Chris Sloan]

I was thinking golden-crowned because of the yellow spot on the head and the bill seems dark for a white-crown???

From what I understand, this sparrow IS leucistic and if I want to be more specific I could say Isabelline, right?

Thanks!

The yellow looks like pollen; notice how it also has some around the bill. It could be a Golden-crown; the bill is definitely dark. I was reacting more to the shape; it shows that very flat-crowned look that is more typical of White-crown. That said, Golden-crown is in the same genus, so could be.

[Christian Dionne]

Thanks Chris!

[John Chardine]

Isabellinism is a form of leucism. Leucism simply refers to any reduction of the ability to produce pigment pigment.

Agreed.

At least conceptually, it seems convenient to consider isabellinism and albinism as different forms of leucism. However, from the standpoint of causation, it seems to be unclear at this point whether they are just phenotypic grades from a single cause fundamentally different in causation. I'm trying to dig up any papers that might address this.