Friday, June 2, 2017

Tree Swallow

I photographed this Tree Swallow in the St. Olaf College playing fields on 25 May 2014. Males of this species are blue above and white below. I was not sure what to make of the brown edges of this bird’s white underparts. Young Tree Swallows are brown and white. Female Tree Swallows take a couple of years to lose this brown color and can be quite variable. Eventually, they are inseparable from their mates (Winkler et al. 2011).

Another hint that this bird is a female is the crease in the center of her breast—presumably where her feathers part to expose her brood patch. This patch is the bare skin with which she incubates her eggs.

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