|Albinistic Western Gull. San Diego, California. October 4, 2014. Greg Gillson.|
While some birders were hoping the leaders would announce to them it was a Glaucous Gull, I recognized immediately that the only large gulls that white were albinos. Size, seasonal expectation, and the thick bill reveals that this is a locally-resident Western Gull.
White feather lack melanin, which imparts strength to the feathers. Thus the white feather tips are abnormally worn--not molting, even though I believe this gull is only a few months old--a juvenile. This bird, if it lives that long (albinos rarely survive long), will get new feathers through molt next September. It will be really ratty by then. Again, if it somehow survives.
Fully albino birds, such as this one appears to be, are not that frequent, but partially color-challenged birds are not that uncommon, especially in black birds such as crows and blackbirds. Birders who observe and identify unknown birds based on shape will not be fooled.
Below is a normally-colored juvenile Western Gull of the same age from our trip--what the top bird should look like.
|Western Gull. Offshore San Diego, California. October 4, 2014. Greg Gillson.|