Re: [cobirds] Bushtit Range Expansion

You might look at the results of the two breeding bird atlas efforts to look for some indication of range expansion, but these will predate the past 10-15 years, mostly. You can also look at eBird species maps for particular years and compare things among years. This is somewhat anecdotal, as it is based on what people happened to have reported (and there has been a marked increase in eBird use over that time period) but might have some useful info. Trend info from the North American Breeding Bird Survey might be of interest, too, looking at results of particular routes or the state as a whole. But these will emphasize roadside results in less developed areas away from some of the more developed regions where Bushtits are perhaps most frequent.

David

On Thu, Dec 4, 2025 at 2:25 PM Virginia Holman <virginiaholmanwrites@gmail.com> wrote:

Hi,

Are there any studies/reports re: the Bushtit range expansion in Colorado in the last 10-15 years? 

I'm coming across significant anecdotal information from longtime birders in the region, but nothing formal/science-based yet.

Thanks for any guidance.

Virginia Holman

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