|
|
Coordinators: 1cy June 2cy Jan 3cy Jan adult Jan |
Ring-billed Gull delawarensis adult, March 18 2012, Virginia Lake, Reno, Washoe Co, Nevada. Picture: Fugle.See Fugle on Flickr. Spring adult with a distinct pink cast probably caused by a carotenoid pigment (astaxanthin) picked up during feeding. Salmon hatcheries--where the pigment is deployed as a food additive to color the flesh--have been suggested as a source for the astaxanthin, but natural food chains are also a possibility. I didn’t notice pink gulls at Virginia Lake until 2005 (though I could have overlooked them earlier). They first turn up in late February/early March & I never see the last one after mid-April [by May most Ring-bills have departed for the breeding grounds]. The percentage of pink birds varies a little but is never more than 5% of the total Ring-bill flock at any given time & is usually only 1-2%. The intensity of the pink also varies, from barely detectable to quite pronounced (as here).
|
delawarensis Ring-billed Gull