One of the first things we birders in the eastern half of the continent learn is that the only hummingbird that ranges here is the Ruby-throat. Like all good rules, this is true, but like most good rules, there are important exceptions. As August works its way into September, the hummingbirds at our feeders really are just about entirely Ruby-throats, and because that is true, few people scrutinize them just in case there’s an inconspicuous outlier among them. But the outliers may be more than curiosities and cool checks on our birding lists. If we keep track of them over the years, especially in the context of citizen science projects such as eBird, our records may help provide valuable insights into such environmental issues as climate change and tropical deforestation.
Over the years, I’ve seen a handful of non-Ruby-throated Hummingbirds in Minnesota and Wisconsin: an Anna’s Hummingbird in Grand Marais in November 1991 (a species normally found in the far West from Arizona and Baja California through Oregon, Washington, and sometimes along the Pacific Coast of Canada and southern Alaska), and a Calliope Hummingbird in the Twin Cities in December 1994 (this one doesn’t have as limited a western range, nesting in the Rockies, regularly migrating through Wyoming, Colorado, and New Mexico, and more birds now and then wandering east). I also saw a Mexican Violetear in La Crosse in October 1998 (a tropical species, but occasionally a stray individual turns up in the United States). No one seems to have worked out a pattern to the violetear's wandering, but some individuals may have a weird genetic mutation that sends them in the wrong direction.
Some of these outlier hummingbirds do die while out of range, as all hummingbirds eventually do even within their range. No one knows if a significant number of them ever find their way back to their natural range, but it’s possible that in a future where their normal range no longer supports them due to fires, droughts, deforestation, or other issues, those with a wandering gene may be the ancestors of survivors in the murky future. A changing climate will change the ranges of a lot of wildlife, benefitting a few species even as it wipes out others.
The western hummingbird that wanders east the most often is the Rufous Hummingbird. I’ve seen them in Minnesota and Wisconsin on a few occasions, including in my own backyard every day for over two weeks in November 2004 (when I took all the photos used on this blog post).
The brilliant naturalist and hummingbird-bander Scott Weidensaul was one of the first to suggest that Rufous Hummingbirds are almost certainly in the process of evolving a new migratory pattern and wintering range. On his website, he states:
Changes in the landscape, and the ever-warmer winters of the past century, may be combining to make the East and especially the Southeast perfectly hospitable to these birds. Those that survive and return to their breeding grounds are, in all likelihood, passing on their once-unfavorable genes to new generations. Banding studies in the East suggest the number of wintering hummingbirds is increasing dramatically, and that we may be seeing the rapid evolution of a new migratory route and wintering area for these birds.
Although most Eastern homeowners take down their hummingbird feeders when the last rubythroats depart in September, these western species don't usually appear until much later in the fall - October, November or even December in the latitude of Pennsylvania. For that reason, it's a good idea to leave at least one feeder up and filled through at least Thanksgiving, even if it freezes at night - and to contact a bander if you have a hummingbird in late autumn or winter.
These hummingbirds do not need to be "rescued," as they sometimes are by well-meaning but misguided people who think it is better to keep them in captivity, or ship them south. This is illegal as well as unwise. The hummingbirds are healthy and well-adapted to their new situation, and have already migrated thousands of miles to get there. Please enjoy them, but don't interfere.