I had two Peterson Western United States bird guides, one from 1990 and another from 2010. Before I gave away the older one, I went through both books page by page, noting if any species’ range maps had changed in that time.

Most of the ranges looked similar to their older version, but some showed a trend in which the changes either revealed more northern or higher elevation ranges. No exceptions to those changes. I marked the pages for those species with !! (“keep watch”).

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