Welcome to the Kirtland's Warbler GeoTrail (KWGT). This trail will take you in a loop in central Northern Michigan through the Jack Pine ecosystem, breeding home of the Kirtland's Warbler. This tour takes you to a total of 25 caches with an amazing trackable geocoin as a reward. The KWGT Passport can be downloaded here: https://f81c572e-1d95-4026-befc-8c60f69cbcd9.filesusr.com/ugd/31e003_41b2f3aa918442e8b08c880e746e6946.pdf
Kirtland's Warblers nest primarily in Northern Michigan, with a few pairs in Wisconsin and Ontario. The majority of Kirtland's winter in The Bahamas, a journey of about 1700 miles.
Migration is the least known aspect of Kirtland's Warbler life history, and the most dangerous period of their lives. In migration, they tend to be found along shorelines of large water bodies such as Lake Erie, the Atlantic Ocean, and the Gulf of Mexico. They stop over in scrubby habitat, similar to what they use in both their winter and summer homes, where they refuel on insects and occasional fruit. Kirtland's migrate in a loop pattern, using a more westerly path in the spring, and more easterly in the fall. The accompanying map (from Cooper et al.) shows the average spring (solid line) and fall (dashed line) migration routes of 27 Kirtland's Warblers fitted with geolocators. Spring migration also happens over a shorter period, with a date range of 59 days, compared to 86 days in the fall.
Map of fall (a) and spring (b) stopover locations for migrating male Kirtland’s Warblers fitted with geolocators (Cooper et al. 2017).
In the spring, Kirtland's generally start heading north about mid to late April to early May, arriving on the breeding grounds as early as 1 May, with an average arrival date of 12 May, and most are here by the end of May. The earliest migration date is 12 April in Florida, and the latest is 9 June in Ohio. A study found it took an average of 16 days for Kirtland's to get to the breeding grounds. The majority of spring records come from Magee Marsh in Ohio and Point Pelee in Ontario.
Map of fall and spring Kirtland's Warbler migration records (Petrucha et al. 2013)
Fall migration is more drawn out. After breeding, most Kirtland's Warblers start heading south from late August to late September. The earliest fall migration date is 1 August, and the latest is 26 November, both in Florida. Kirtland's average 18 days in the fall to arrive on the wintering grounds.
Cache
I caught and color-banded a young Kirtland’s Warbler about a half mile southwest of here in 1996. I was banding Kirtland’s near Gwinn in the UP in 1999 and recaptured that same bird, a distance of about 300 miles.
Sources
Cooper, N. W., M. T. Hallworth, and P. P. Marra. 2017. Light-level geolocation reveals wintering distribution, migration routes, and primary stopover locations of an endangered long-distance migratory songbird. Journal of Avian Biology 48:209-219.
Petrucha, M. E., P. W. Sykes, Jr., P. W. Huber, and W. W. Duncan. 2013. Spring and fall migrations of the Kirtland's Warbler (Setophaga kirtlandii). North American Birds 66:382-427.