Saturday, March 12, 2016
Yellow House Finch
I assumed that these yellow variants are the result of their having high levels of beta-carotene or with low levels of echinenone (either because of what they are eating or because they are unable to metabolize these hormones). See my 2012 post on a yellow House Finch in California.
The situation may be more complicated. LaBarbera (in Toughlittlebirds.com) has an interesting blog post. She writes that red males often hold the richest territories. Younger females are attracted to these wealthy birds. Red males, however, do not raise their young as fastidiously as do yellow males.
Yellow males breed later and and take better care of their young. Older females prefer to mate with these more stalwart males. I have simplified LaBarbera’s report, which includes further variables in this hypothesis. For example, it may be advantageous for a younger male to be red and then become yellow in subsequent breeding seasons. You will find LaBarbera’s post to be fascinating.
Posted by Dan Tallman at 8:45 AM