Various, Arapahoe & Jefferson

[Hugh Kingery]

A miscellany of observations:

A Rufous Hummingbird visited the Denver Audubon Nature Center July 2. Seen by the Denver Audubon group on Walk the Wetlands.

A Lark Bunting seen east of Castle Rock on Upper Lake Gulch Road, June 30, by Sharon Hines. Apropos of Jared Del Rosso's 2 observations in western Arapahoe County the same day.

On our Cheesman Lake BBS route, June 30, we heard/saw 
    23 Green-tailed Towhees -- 5 times the previous high count -- and
    16 Rock Wrens, 3 times the previous high count.
Why the high towhee numbers I'm not sure (unless I've improved at identifying its song) but Rock Wrens have increased due to Habitat change. They have burgeoned in the aftermath of the 2002 Hayman Fire, and to a lesser extent, the 1996 Buffalo Creek Fire.

    We also counted 31 Western Tanagers, not a record but still a high count and 30 Broad-tailed Humm.

Hugh Kingery
Franktown, CO

[Paula Hansley]

I have counted many fewer green-tailed towhees and some other species (i. e., Dusky and Hammond's flycatchers in Golden Gate Canyon State Park and upper Coal Creek Canyon where there was nearly 4' of snow in late May. Perhaps they moved to lower altitudes?  Same could be true of rock wrens. 

Paula

Sent from my iPhone

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[Tim Johnson]

In RMNP the last 2 weekend days we saw many more Green-tailed Towhees than usual. We hiked in Wild Basin and Upper Beaver Meadows at about 8000 feet. No Rock Wrens, however. It was the only species that had increased numbers, however; warblers and sparrow numbers seemed to be down. Candice Johnson, Denver

[Hugh Kingery]

The elevation for the Cheesman BBS route spans 6800 to 7800 feet. I think the bird changes relate to habitat more than to refugees from Golden Gate. Certainly the Rock Wrens have populated the Hayman Fire area. This, even 15 years later, sports bare hillsides and grass-covered hillsides with many standing dead trees but, for the Rock Wrens, meadow-like hillsides and on the ground, dead trees  lying at all angles, and also has exposed rock outcroppings.
    The Green-tailed towhees sing from fire-tinged hillsides which have some shrubs.
    The Hammond's Flycatchers used to inhabit the ponderosa woodlands along the first part of the route, the part that the Hayman fire changed drastically into Rock Wren habitat. Their habitat is gone gone gone.

Hugh Kingery
Franktown, CO

[DAVID A LEATHERMAN]

Hugh et al,

I always regarded "shrub" birds like green-tailed towhee to be one of the big winners in the aftermath of what ecologists call "disturbance events".  When forest overstories are removed by beetle epidemics and fires, birds that like early succession plant communities have the world come their direction.  So, yes, I think your assessment of "habitat change" as a major factor in BBS number changes near the Hayman Fire is probably correct.  I also think, as Paula suggests, there are seasonal shifts in populations in response to weather issues, food abundance, condition of a particular area when migrants first arrive, etc.  The amazing data set that BBS constitutes is invaluable in helping sort out these changes of both a short and long-term nature.

Interestingly and perhaps related, when I helped Nat Warning (now working for State of Maryland DNR) with his very interesting graduate studies of Canyon and Rock Wrens up at Horsetooth Reservoir west of Fort Collins, we found that even when the two species nest in very close proximity, they forage differently.  The Canyon Wrens came to the nest with prey that obviously mostly came from rocks and caves (lots of spiders, centipedes and crane flies), the Rock Wrens more often went out in the meadows near the rocks to find the majority of their nestling fare (more moths, flies, grasshoppers and beetles).

Dave Leatherman

Fort Collins

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From: 'Hugh Kingery' via Colorado Birds <cob...@googlegroups.com>
Sent: Monday, July 3, 2017 2:40 PM
To: redstar...@gmail.com; cob...@googlegroups.com
Subject: [cobirds] Re: green-tailed towhees and rock wrens - Jefferson

 

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[Chip Clouse]

I had only one Green-tailed Towhee on my Great Divide BBS route in Moffat County when I've been in double digits, even approaching 20, every year over the past 4 years.

Chip Clouse 

Golden, CO

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