Of Mousebirds and Bushtits: Rules for Gregarious Gray Family Groups

bushtits

A family group of Bushtits clamber around a suet feeder in North America.

This is one of those easy comparisons that any birder with experience in western North America and sub-Saharan Africa can make. Growing up in California, I was quite familiar with Bushtits. Little gray birds with long tails and stubby bills, they move from bush to bush in open country in family groups of ten to thirty individuals, often with total disregard for a human standing nearby. Their gregarious habits, clambering around vines and vegetation, hanging upside down,  chattering little “sip” notes to each other, are conspicuous. They are a party unto themselves.

mousebirds

A family group of Mousebirds sleep together on a branch in Africa.

So I was astonished to be walking across the grounds of Bunda College in Malawi when a group of over-sized Bushtits came my way. Though larger than our Bushtits, and with crests, their mouse gray plumage and group behavior, bounding bird after bird from bush to bush calling to each other, was identical to the Bushtits back home. I was astonished at the similarity.

Interestingly, both locate their nests near danger to ward off predators– Bushtits commonly nest above human walking paths, while Mousebirds choose to locate near wasp nests.

While these videos don’t show the characteristic way the flocks move from bush to bush, they do illustrate their communal behavior.  Compare these Bushtits coming to water

with these Mousebirds at some fruit:

Bushtits are from the order Passeriformes (songbirds).  Their family includes ten other “bushtits” in Eurasia, such as the Long-tailed Tit.  They evolved rather recently, about 14

mousebirdbushtit

Left: Mousebird in Africa. Right: Bushtit in North America.

million years ago. Mousebirds, on the other hand, aren’t even Passerines; they are from the order Coliiformes, one of the most ancient lineages of Aves (Birds).  Mousebirds and Bushtits last had a common ancestor over 65 million years ago, and yet have evolved to fill some peculiar niche in certain semi-open habitats in different places around the world. Somehow this behavior fits into the great ecological jigsaw puzzle, and they each, separately, evolved to fill that niche.

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