Can anyone identify this small yellow/brown bird in my Garden

Hi,

this is not a House sparrow :))  It's probably a leucistic  american Savannah Sparrow :))

S

Is it usual to see such a sparrow in the UK?

Bev C said:

 i thought this as well leukistic female house sparrow thought this may have been what bird mum see the other day fly out of a bush with black bird female black bird with slight leukistic

Hi, 

I was replying to this post from Bev- THIS is a  leucistic savannah sparrow :)))  It is very rare in the UK and this photo was taken in the USA :))

S

sorry did i confuse  people with the image i posted

I've long been confused about the terminology for different colour mutations in birds, but someone directed me to this paper: http://www.vogelringschier.nl/DB28%282%2979-89_2006.pdf which makes all clear (well, a lot clearer).

According to this, the leucism mutation causes all-white feathers (not necessarily on the whole bird) by removing the two kinds of melanin (black/grey and red/brown) that colour birds' feathers. Unlike albinism, though, it doesn't affect the eyes, so even 100% leucistic birds have normal eyesight as well as normal eye colour and so survive much better than true pink-eyed albinos which have terrible eyesight.

Going by the article, this house sparrow is not leucistic but has one of the two mutations that causes reduced black/grey melanin. This means the red/brown melanin dominates, producing an all light brown bird.  The author calls them 'brown' (when the black/grey melanin is chemically altered so it doesn't 'work' properly) or 'isabel' (when the black/grey melanin is reduced or absent).