greenfinches

[oasisjack]

Does anyone know why some greenfinches in my garden are significantly darker than others? They seem to be a minority but not by much. The darker ones mix perfectly well with the rest but are a lot browner than the typical green and yellow. Is it a gender difference, genetic variation, or even a different race?

[Emma]

Female greenfinches are brown - it's only the males who are that lovely green colour.