Thousands of birders, photographers, and curious folks will converge in the northwest portion of Ohio this year for the festivities of the Biggest Week in American Birding.  And with good reason.  Western Lake Erie is home to possibly the very best Eastern wood warbler experience on the North American continent in May.  There are 36 species of warblers that occur in Ohio every year.  And away from the nesting grounds in Michigan, Ohio is the best place to look for a 37th species, the Kirtland’s Warbler.  Swainson’s Warblers nest in neighboring West Virginia, but only a handful of records exist for Ohio.  So that species is not to be anticipated.   I’ll get to the regular 36 (plus Kirtland’s) in a bit.

What is the best time in Ohio to see warblers?  That’s a good question.  Many birders here will tell you May.  And that is true.  But the numbers and variety of species varies week-to-week.  And weather conditions affect the number of birds, too.  That brings me back to the original question: what is the best week to come to Ohio for warblers?  If you went searching for warblers in Southern Ohio, you might find some species a week or two before they arrive in Northwestern Ohio.  And how does one measure “best”?  Ahhh.  Well, you could use…data.  Thanks to the efforts of many, many folks we now have some data.  While not exact, for sure, it’s the best information that’s currently available.  I downloaded data from eBird version 3.  Official citation here:

eBird. 2011. eBird: An online database of bird distribution and abundance [web application]. Version 3. eBird, Ithaca, New York. Available: http://www.ebird.org. (Accessed: March 2, 2011).

Do you use eBird?  I certainly hope so.  Your every day contributions are valuable.  Just a note of caution here.  The data that I am using has some data from unpopulated areas (namely Adams & Scioto Counties in Southern Ohio).  There is just not a great volume of data from here.  It is far from any large city and has few places to lodge.  Still, I am including those areas because I count them as important bird areas (and also a whole lot of fun to explore).

The best time to visit for warblers?  For all of Ohio statewide, the best weeks in order are the 2nd week of May, the 3rd week of May, and the 1st week of May.  For Northwestern Ohio, the best weeks in order are the 2nd week of May, the 3rd week of May, and the 1st week of May.  For Southern Ohio, the best weeks in order are the 1st week of May, the 4th week of April, and the 2nd week of May. (this according to eBird data).

Below, 37 species of warblers are listed with bar charts showing frequency of observations as a percentage. (note that the scale is *not* the same for each chart)  Essentially, it is the percent of submitted checklists that have this species recorded (without regard to actual numbers).  These charts are only intended to give us a way to conservatively measure the relative distribution of a species for 3 locations: 1) Ohio statewide; 2) Lucas & Ottawa Counties in Northwest Ohio; 3) Adams & Scioto Counties in extreme Southern Ohio.

Here are the locations in Ohio I have used for these charts: