Updated: Aug 29
This is an identification issue that arises frequently in the interior west.
Screech-owls (Megascops) in the intermountain west can be confusing. Even the most experienced birders will avoid arguments on photos of a screech-owl that show intermediate characteristics. Why? It's hard. Many "listers" prefer to get their life-birds by identifying owls using their songs or calls. Gray, secretive, intricately-marked birds are nobody's description of a good time. However, visual identification of a screech-owl is NOT impossible. (There are always exceptions.)
Today's focus will be on the more obvious traits that can be used to separate these two tough screech-owls. There are a few more features, but they become increasingly intricate in nature, and beyond the scope of this post. To make this easy, use the three B's: bill, barring, and base color. This is an oversimplification that should get you started on the correct path of Megascops identification.
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Identification of the Eastern Screech-Owl (EASO)
In the photo below, note the Eastern Screech-Owl (left) is paler overall. This is likely a result of two factors. The dark barring is less dense, and the base color of the feathers is whiteish. Note the pale bill and the anchor shape of the pattern on the ventral feathers. The barring/streaking is less dense especially in the throat and ear tufts (or plumicorns). These traits can all vary wildly, but a proper combination can lead to a positive identification.
Identification of the Western Screech-Owl (WESO)
Using the same photo as above, note the darker overall color of the Western Screech-Owl (right). The dark barring is dense, and the base color is more gray than white. The bill is dark and instead of an anchor shape, the horizontal bars stay perpendicular to the vertical streaks. The barring/streaking is very dense on the tufts (plumicorns), throat, and face. Bill color in some Western Screech-Owl subspecies can be pale. So again, use a combination of traits that can lead to a positive identification.
We will focus on the two most visible areas on screech-owls (when seen): the patterning on the ventral portions of the body, and the field marks on the face and head.
Now, let's compare the two birds side-by-side with major ID factors circled in red.. Look at barring, streaking, and base feather color. The higher density of barring, streaking, and other markings often give the Western Screech-Owl a darker overall appearance than the Eastern Screech-Owl.
In this next graphic, I provide a VERY rough sketch of the pattern we would expect to see on the ventral feathers of an Eastern Screech-Owl vs a Western Screech-Owl. I used a base color for each feather, pulled from actual photos of each species. The base color can be highly variable, though many Western Screech-Owls have a darker base color. Pay attention to the shape and pattern, the thickness and density of the barring, AND the streaking thickness. Also, note the density of the horizontal barring on each feather. Western Screech-Owls OFTEN show more bars per feather, than Eastern Screech-Owls.
Eastern Screech-Owls often show an "anchor" shape, as the horizontal bars point anteriorly (up). The Western Screech-Owl has "flat" horizontal bars, that can show some anterior pointing, but it is usually minimal. The vertical streaking can often appear to be much thicker in the Western Screech-Owl, though, some of the photos used in this post do not show a good representation of this trait.
The base color of the ventral feathers can often be helpful, however, there are exceptions to this rule. See the next two graphics for examples of exceptions. While the base color can be lighter on the Western Screech-Owl, the extensive barring can still give WESO a darker appearance.
This rufous coloration is seen in the rufous morph of the Eastern Screech-Owl. If you see a "red" screech-owl, you can almost certainly assume it is an EASO. See this "red" EASO individual below.
In this final image, compare the bill color and the density of barring on the ear tufts, facial disks, throat, and "eyebrows." Western Screech-Owls generally have darker bills, and dense, extensive barring on the facial areas, than Eastern Screech-Owls.
Screech Owl Range Maps for the US
Use your keys from the top of the post to identify these two mystery owls. Answers are at the bottom of the post.
Final Thoughts on Screech-Owl Identification
No single trait should EVER be used to identify a screech-owl without significant experience identifying individuals in this genus. Also, this post does not cover the extreme variation experienced in the subspecies of these Megascops owls. And for the final smack of our optics, individual variation in screech-owls can be extensive. Ask questions, identify birds slowly and deliberately, and take as many photos (and/or recordings) as you can. And remember your three B's: bill, barring, base color.
So, how do you confidently identify a silent screech-owl? Beats me. Maybe try underwater basket weaving? Or... subscribe (CLICK HERE) to this blog and maybe one day we will solve this together. Or we can just complain together.
Owl 1 - WESO - Dense, thick barring, heavy face/head barring and streaking, darker overall, and a dark bill.
Owl 2 - EASO - Less dense barring, bars point anteriorly, the base color is light (with a hint of rufous), the face is not as heavily marked, and the bill is light.
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In order of appearance:
Western Screech-Owl flickr photo by Alan Schmierer under the CC0 1.0 Public Domain Dedication. Modified from original for use.
Rufous morph Eastern Screech-Owl by Joshua J. Cotten on Upsplash.
Western Screech-Owl flickr photo by Dominic Sherony under a CC BY-SA 2.0. Modified from original for use.
Eastern Screech-Owl flickr photo by DaPuglet under a CC BY-SA 2.0. Modified from original for use.
Western Screech-Owl flickr photo by William Herron under a CC BY-SA 2.0. Modified from original for use.
Eastern Screech-Owl flickr photo by Rita Wiskowski under a Public Domain Mark 1.0. Modified from original for use.