This morning while out photographing birds at a local wildlife refuge I came across this Red-winged Blackbird with a strongly crossed bill, which of course is not typical of the species. I’ve seen a few mildly crossed bills in this and other species in the past but never one quite this pronounced in a species where it isn’t “normal”.
Red-winged Blackbird with a crossed bill, perched on curley dock
There are species of birds in North America that have crossed bills as a species trait – the Red Crossbill and the White-winged Crossbill. Their crossed bills are an adaptation for extracting seeds from cones. Seeing this RWBB with a crossed bill naturally got me thinking about evolution. Variations occur throughout nature since each individual inherits a different combination of genes from its parents. This particular variation would likely be selected against in RWBB’s and would not persist since they do not typically pry seeds from cones. However, one can see how this same variation in the ancestors of todays crossbills would be the genetic fuel for the crossed bill trait they all exhibit today.