Cumberland

Among the southern (and western) rarities being reported in Maine this spring, there seemed to be a noticeable uptick in the number of Blue-gray Gnatcatchers being reported. This is a continuing trend that birders have noticed over the last couple years as this species is slowly expanding its range in the northeast. Thanks to birders submitting their checklists to eBird, we can visualize how this increase has taken place fairly dramatically over just the past few years. Lets use eBird to explore this change from 2012 to present day:

This can most easily be done by viewing the frequency, or percentage of total checklists, that Blue-gray Gnatcatchers are being reported on. By clicking through each of the following years, you’ll see how the frequency of 2012 peaked at 2.4%, in 2013 the peak increased to 2.8%, and in 2014 it took a large jump to peaking at 3.8% for the spring migration.

You can do this yourself [for any species] by clicking on the ‘Explore Data‘ tab and then selecting ‘Line Graphs’. You’ll then be promoted to ‘select a species’ and there you’ll see your chart! You can test yourself by trying a control group: create a line graph for Chipping Sparrows in Maine, a species with a very stable population. Compare 2012, 2013, and 2014 and notice how little variation there is from year to year.

For a visual that is easier to compare, you can download the histogram data from each of the line graphs that you’ve created and then create a graph in your preferred spreadsheet software. Below is a chart showing how each spring the Blue-gray Gnatcatcher peak frequency has been increasing. The line for 2014 cuts off in the second week of June (the time of this article being published) so we can only wonder what the fall migration peak will look like this year. So get out there, look for birds and report what you see. Your odds look pretty good for finding a Blue-gray Gnatcatcher in the last week of September!