Wilson Warblers-Crow Valley-CG

[Robert Righter]

Hi all

While birding for two hours this morning, I detected 30 migrating Wilson’s Warblers. The vast majority were seen in thickets, not so much in the trees. So did I see all the Wilson’s Warblers in the campground? Most likely not. Given the inventory of thickets in the region, could I reasonable assume I only saw about half of the actual number—most likely so.  The Wilson Warbler’s breeding range stretches from the Pacific ocean to the Atlantic Ocean, although the warbler is more common in the west than in the east.  Since I was only in the region for two hours, what could this information mean towards calculating the total population for this warbler. Since the campground is just a mere speck in the totality of the warbler’s migrating range and just a moment in time, would it be reasonable to assume the total population for the warbler to be in the millions, hundreds of millions or……?

Given the above example, what would others estimate Wilson’s Warbler total population to be?

Bob Righter

Denver CO

[nic korte]

Here’s what Cornell’s “All About Birds,” says:  Wilson’s Warbler populations declined by nearly 2% per year between 1966 and 2015, resulting in a cumulative decline of 61% according to the North American Breeding Bird Survey. Populations in the West are declining at a greater rate than populations in the East. Despite these declines, they are not listed on the 2016 State of North America’s Birds Watch List, however the 2014 State of the Birds Report listed Wilson’s Warbler as a Common Bird in Steep Decline. Partners in Flight estimates a global breeding population of 60 million with 61% spending some part of the year in the U.S.

 

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[David Suddjian]

There is a suggestion here maybe to extrapolate a good migrant concentration at one place to fit it to the whole landscape, or similar areas. But I think there is seldom evenness to the distribution of such migrant landbirds. As an isolated grove, maybe the trees of Crow Valley were a draw to bring warblers to concentrate in that general area, even if they were foraging in the thickets?

I had just one Wilson's in my patch near home this morning at Ken Caryl. I could extrapolate that to balance the Crow Valley bounty :-)

David Suddjian  

Ken Caryl Valley

Littleton, CO

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[wmrki...@gmail.com]

And this afternoon I had two Wilson's in my back yard (Berkeley neighborhood Denver) - new yard birds for me!

Bill Killam