[cobirds] Worm-eating shrikes, Crowley & Lincoln Counties; and other matters

Hey, all.

Here's a thought. Loggerhead Shrikes are absent in winter from northeastern Colorado, yet widespread in winter in the Arkansas River drainage of southeastern Colorado. There aren't many other passerines with distributions like that. Mountain Bluebird approximates that distributional pattern, but it's a pretty weak approximation; Sage Thrasher approximates it even more weakly. Which raises a question: What is it about southeastern Colorado that appeals to wintering Loggerhead Shrikes?

Yesterday afternoon, Sun., Feb. 11, Hannah Floyd and Andrew Floyd and I pondered the matter as we observed at least 7 Loggerhead Shrikes along and near Colorado Route 71 from Ordway north to southern Lincoln County. The shrikes were actively and efficiently foraging on caterpillars in the shortgrass prairie. Here's a photo of one of the shrikes and its prey:

As usual, click on the image to enlarge. Heidi Eaton tells us that these appear to be the caterpillars of the army cutworm, Euxoa auxiliaris, a.k.a. the "miller moth."

I wonder if the situation is ecologically analogous to the Mountain Bluebirds feasting on the caterpillars of tiger moths in the genus Grammia. Dave Leatherman has opened our eyes to this phenomenon. The basic idea is that the distribution in late winter and early spring of such species as Loggerhead Shrike and Mountain Bluebird might be limited in part by the availability of these juicy, abundant, terrestrial caterpillars. And I'll tell you this: Once you get north of southern Lincoln County on 71, the terrain quickly goes from semi-tropical to the cold depths of interstellar space. There are no unfrozen caterpillars there.

A few other roadside birds from this past weekend down in southeastern Colorado were headlined by this stunner:

This Indian Peafowl was just ambling along U.S. 50 near Bent County Road 6.25. We decided that there are two types of humans in this world: Those who delight in serendipitous encounters with the most spectacular bird on Earth and those who are joyless pedants. Farther east along U.S. 50, in Prowers County, we saw these roadside birds:

Here's more of the flock, at closer range:

They are Great-tailed Grackles, and they made funny sounds.

Along U.S. 385, Prowers County, we saw this Scaled Quail watching us from the other side of a chainlink fence:

We actually did get off the main highways from time to time. At Hasty Campground, John Martin Reservoir State Park, Bent County, on Sunday morning, Feb. 11, we found a Swamp Sparrow, a Marsh Wren, a Ladder-backed Woodpecker, a wayward Black-capped Chickadee, and Hooded Mergansers and Ruddy Ducks. And Snow Geese! For 30+ minutes we watched a non-stop procession from the east. Just a handful of Ross's Geese mixed in, best we could tell. Anyhow we could see--and hear!--that the geese were putting down on the reservoir proper, so we went up to the dam where we saw 100,000 Snow Geese. We sorted through the flock a second time, and again got an exact count of 100,000 Snow Geese. (That's a joke. Joyless pedant alert. Anyhow, a lot of geese.)

Let's see, what else? I mentioned a couple days ago that Willow Creek Park, behind Lamar Community College, was decently birdy but frigid, with our highlights being an auduboni Hermit Thrush and a previously reported iliaca Fox Sparrow. Two Buttes State Wildlife Area, Baca County, was even more frigid when we birded there on Saturday afternoon, Feb. 10, but we found some nice birds, highlighted by Rusty Blackbird, Winter Wren, and Northern Mockingbird. Also flyover Sandhill Cranes, Rock Wren and Canyon Wren, 30+ Pine Siskins, several Townsend's Solitaires, flyover longspurs (maybe chestnuts?), and Mountain Bluebirds galore. Like this guy:

Lake Henry, Crowley County, was frozen solid. Bummer. Lots of Bald Eagles there, though, waiting for the dead fish and influx of rare gulls. Maybe this coming weekend? Box Springs Pond, just off Colorado Route 71, extreme northern Crowley County, had a Marsh Wren chippering away. Lots of raptors there and in the general vicinity, including Harlan's Hawk, Great Horned Owl, Prairie Falcon, Rough-legged Hawk, Golden Eagle, and Northern Harrier.

A final remark. All the birding and bugging and general merrymaking was in connection with the 16th annual High Plains Snow Goose Festival, based out of Lamar, Prowers County. The folks in Lamar are already scheming for the 17th festival, February 2019. 

Ted Floyd

Lafayette, Boulder County

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