Tomorrow, the winter solstice in Wisconsin welcomes the shortest day of the year, clocking in at 8 hours 59 minutes. Half the world over, in the Panama Canal sits Barro Colorado Island, almost 6 square miles of some of the most-studied tropical forest in the world (the Smithsonian houses a research institute on the island). Tomorrow, the day length on Barro Colorado will last over 11 hours and 30 minutes. On this island you may find Bay-breasted warblers, foraging through the rainforest in mixed flocks.
Bay-breasted warbler, photo by Dave Inman
The Bay-breasted warbler is a common migrant through Wisconsin each year. On certain days in May these birds seem to swarm through the state. This past May I was on the Crawfish River kayaking and witnessed over two dozen Bay-breasted warblers in just a half hour. Breathtaking in their foraging and plumage, these warblers hop and hover in a flurry of activity, all the while adorning the trees with their decorative chestnut breasts and flanks and cream underparts and rear cheek.
Canadian boreal forests are prime breeding habitat for Bay-breasted warblers. These birds will utilize spruce trees, placing a nest in the bottom third of the tree, and taking advantage of spruce budworm outbreaks for a great source of nutrition for both parents and young. Wisconsin’s Atlas of the Breeding Birds of Wisconsin remarks, “This is one that got away!” since no breeding was documented in the first Atlas. In Wisconsin’s recently completed second Atlas, no Bay-breasted warblers were documented, even as probable breeders. While northern Wisconsin has suitable boreal habitat in certain areas, these are not massive tracts like the Canadian boreal forest, and accessing many of these swampy areas can be extremely difficult. Confounding the effort of finding breeding Bay-breasted warblers in Wisconsin is the fact of climate change—as the climate warms these birds may abandon more southern boreal forests.
Bay-breasted warbler, photo by Andy Reago & Chrissy McClarren
Back at Barro Colorado Island, researchers found that Bay-breasted warblers were not specialist foragers on their wintering grounds. While the birds specialize on spruce budworm on breeding grounds, they can be found in Panama anywhere from roadsides to lawns to garbage cans. I like to think about their sun-drenched wintering grounds as daylight wanes at Faville Grove.
Written by Drew Harry, Faville Grove Sanctuary land steward
Cover photo by Stan Lupo
