Wednesday 24 June 2020

[cobirds] Rocky Mountain Arsenal- Grasshopper and Cassin's Sparrow galore and a Bull Snake/Oriole predation event. Oh My!

Celebrating my friend Bryce's 72nd BDay started with an Arsenal run, then sourdough blackberry pancakes for very late brunch.  We birded many areas along 64th, then the auto tour loop. Lots of traffic on road and trails, no masks in evidence or any attempt at social distancing except our little group. There about 4 hours. 

The morning started surprisingly with 8 territorial male Cassin's Sparrow's singing on both sides of the road near the first porta-lets and continuing to the entrance to the refuge.  Horned Larks also presented in numbers which is also surprising. There was a great mix of songbirds along the 64th from the visitor center to where the road turns left (north) from 64th.  Highlights include Grasshopper Sparrows calling immediately by the road at Mile Marker 4 and near MM5, Blue Grosbeaks at Lake Ladore and 64th and near MM3, a rock wren making enough racket to wake the dead on the dike at Lower Derby, lots of young of many species including Western Wood-Pewee, Red-tailed and Swainson's Hawks, young and adult groups of Lark Sparrows, grackle families mixed with starling gangs,  It was pretty warm by the time we got to the northern end of the Auto Loop and Burrowing Owl territory.  No hits but on the way out just past the exit from the Bison area eagle-eyed Lisa spotted a young Great Horned Owl sitting in the shade under a tree trying very hard to look like a cat.  Great fun. 58 species.  A few documentary photos made but all on antique I-phones so not worth posting.  So you get a breakfast picture instead.

We watched a Bullocks Oriole nest predation from start to finish. We were attracted to a cacophony of Orioles in a cottonwood. As we got closer, I could see the birds mobbing something. A little closer and I could see a snake crawling along a branch about 10' up in a large Plains Cottonwood. Despite repeated strikes to the body and head, it kept working its ways along and around a variety of branches till it found the nest.. Without a pause, it entered head first into the nest and about 6-8 inches of its body went in with the orioles screaming and striking at it. Approx. 7 minutes later it backed out of the nest and proceeded to find its way back up the branch and away. The orioles keep up their cacophony throughout until it completely left the area. In addition to 6-8 orioles, mostly males, a Downy Woodpecker, Blue Jay and Warbling Vireo joined the fracas. Cowbirds were also in the area but didn't join in. The Colorado Bullsnake (Piuophis catenifer sayi) was nearly 3 feet long, and moved very methodically as it searched out the nest then sought a retreat route. When we returned about 10 minutes later, all was quiet and no Orioles approached the nest for at least the next 10 minutes.   

Charlie Chase
Denver

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