[cobirds] eastward range extension of foothill/mt species

Over the past 45 years or so of visiting Fort Collins' Grandview Cemetery and also spending a lot of time on the eastern plains at places like the Pawnee Grasslands and Lamar, the occasional and seemingly increasing presence of foothills/lower mountain species at low elevation has intrigued me.

I have mostly attributed this to maturation of the "urban forest", especially Colorado Blue Spruce but certainly other conifers and many deciduous trees, as well.

Species with the bulk of their breeding habitat in the foothills and lower mountains that sometimes breed in Grandview Cemetery include: red-breasted nuthatch (of late, every year), broad-tailed hummingbird (of late, every year), western wood-pewee (of late, 2 out of every 3 years), chipping sparrow (of late, every other year), ruby-crowned kinglet (of late, every third year), red crossbill (ever(?), once), western tanager (ever(?), once).

Now I am beginning to wonder about cordilleran flycatcher.  In the last couple weeks there have been reports of this species at the prairie-foothills interface from several locations along the Front Range on COBIRDS.  Last weekend I can add another from the River's Edge Natural Area in Loveland (Big Thompson River near the softball complex at the old fairgrounds).  The Loveland bird was a male giving the characteristic territorial "squeek-itt!" call.  Other recent reports have mentioned detection via this same vocalization. 

I have questions.  BBAII accounts indicate one nesting cycle and attribute late nests to renesting after early nest failures.  The "Birds of the World" account for this species mentions the likelihood of two nesting cycles in Oaxaca, MX.  Do the recent reports represent second-try nesting at lower elevation?  Do they represent second nestings at lower elevation after a successful nesting higher up?  Do they represent post-breeding dispersal, with the individuals simply vocalizing in the lower elevation area they moved to as if on territory?  Does the "new normal" of fires and smoke in the mountains of the West have anything to do with what appears to be a shift to lower elevations at this time of year?

We birders need to keep reporting our presence/absence and behavioral observations of all species, including common ones, and I still maintain COBIRDS is a good place to do that.   Thanks to everyone who makes the effort to post to COBIRDS, especially if that means extra effort because you also did an eBird checklist or posted to some other media.  There is no such thing as "excessive" communication.

Dave Leatherman

Fort Collins