Burrowing Owl And Western Screech Owl — Cousins Yet Very Different

You may enlarge any image in this blog by clicking on it.  Click again for a detailed view.

It occurred that it might be worthwhile to talk a bit about the similarities and differences between Western Screech Owls and their cousins, Burrowing Owls.

Let’s start with the similarities.  These little owls are about the same body mass, with the Burrowing Owl being slightly heavier (150g for the Screech Owl, 155g for the Burrowing Owl), although the Burrowing Owl’s long legs give it a taller appearance than the Screech Owl when perched.  Both owls have typical “owl” faces, somewhat dished, with forward facing eyes that seem to be much too large for their heads and that give them binocular vision.  Both owls are colored in earthen tones although the Burrowing Owl is predominately brown whereas the Western Screech Owl is mostly gray.  Here are images of both species, the first being the female Screech Owl that resides in my friend Dan’s yard and the second being a Burrowing Owl that lives in farm country about 30 miles northwest of Tucson.

One other similarity.  Both of these owls, at least in southern Arizona, are desert dwellers.

But, with that, the similarities end. There are some significant differences in appearance and some very significant differences in lifestyle between the two species.  One somewhat oversimplified way of describing the differences may be to say that Screech Owls are evolved to hunt silently and at night whereas Burrowing Owls are evolved to dig burrows.

Western Screech Owls have tiny “horns,” technically, “plumicorns,” that are tufts of feathers on the tops of their heads that the owls can erect when excited or annoyed.  Burrowing Owls lack these features.  Screech Owls have much “fluffier” plumage than Burrowing Owls, plumage that enables them to fly almost silently.  Burrowing Owls, by contrast, have compact plumage that gives them a sleek appearance.  I’m speculating, but my guess is that this compact plumage enables these owls to dig while not trapping dirt in their feathers.  Although not shown clearly in these images, Screech Owls have much larger feet in proportion to their body size than do Burrowing Owls.  Those feet are evolved to give these owls powerful weapons with which to seize prey.  Burrowing Owls’ feet are somewhat less imposing, and are flatter than those of Screech Owls with distinctly longer toes. They may have evolved as digging tools.  Screech Owls have plumage on their legs that extends down to their feet, another evolved trait that assists in silent flight.  Burrowing Owls’ legs are devoid of plumage, which, I suspect, assists them in digging.

One additional physical difference: Screech Owls are sexually dimorphic, meaning that the females of this species are significantly bigger than are the males.  Burrowing Owls show no dimorphism.

Screech Owls favor heavily vegetated terrain within the desert, preferring land that contains trees and dense brush.  Burrowing Owls, by contrast, are inhabitants of open country.  Look for Screech Owls among mesquite and cacti.  Search for Burrowing Owls in prairies or adjacent to cultivated fields.  Screech Owls are cavity nesters, finding homes in recessed features, such as holes in tree trunks.  Burrowing Owls, of course, dig burrows or appropriate the burrows of other species.  Both species are predators and very eclectic in their tastes, hunting anything from large insects to smaller birds, reptiles, and rodents.  But, Screech Owls are exclusively nocturnal in their hunting whereas Burrowing Owls seem to operate round the clock.

How closely related are these two birds?  That’s a good question.  Each belongs to a different genus (the Western Screech Owl belongs to genus Otus and the Burrowing Owl has its own genus, genus Athene). These two species are genetically distinct.  Burrowing Owls have existed in North America for at least two million years so, assuming that the two species have a common ancestor, they diverged millions of years ago.  They’ve obviously wandered down very different evolutionary pathways over the millennia.

Images made with a Canon 5Div.  First image shot with a 100-400mm f4.5-5.6 IS II L zoom lens and illuminated with a Canon 600EX-RT Speedlite, M setting, ISO 320, f8 @ 1/160.  Second image shot with a 400 DO II lens+1.4x telextender, aperture priority setting, ISO 640, f5.6 @ 1/5000.

One Reply to “Burrowing Owl And Western Screech Owl — Cousins Yet Very Different”

  1. […] via Burrowing Owl And Western Screech Owl — Cousins Yet Very Different — Sonoran Images […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Blog at WordPress.com.