Pale Male

Day 233: Somebody bleached one of my Goldfinches! I'm kidding, of course, but although there is some degree of variation as these birds pass from drab winter colours to their yellow summer finery, I have never seen one quite as white as this guy.

Scholars will disagree on whether this variation should be referred to as "partially leucistic" or "dilute." David Allen Sibley says, "The term leucistic has a confused history. In the introductions of the Sibley Guides I said the term leucistic is synonymous with dilute plumage. That usage was fairly common among birders at the time, and I was unaware that it contradicted several scholarly publications (e.g. Buckley 1982, van Grouw 2006) which define leucistic as the total lack of melanin from some or all feathers (what I called partial albino in the guides). It does make sense to distinguish birds that are unable to deposit melanin (my partial albino, their leucistic) from birds that are able to deposit melanin but only in low concentrations (my leucistic, their dilute)...I’ve used the term leucistic (not partial albino) for birds which cannot deposit melanin, which helps to distinguish these birds from the narrowly-defined true albino, and allows use of the term 'partial albino' as a general category for any bird showing any form of reduced melanin."

If you find this confusing, don't fret. It is a good example of how plastic the sciences are. While good scientists like Sibley try to stay abreast of research, it sometimes gallops ahead so rapidly that it's hard to keep up. For now, it seems safer to refer to my washed-out Goldfinch as a "pale male."