Let’s start this article with a few words you probably wouldn’t expect together in a sentence : Alaska. Winter. Hummingbird. Yup, one of Alaska’s rare, winter birds is the Anna’s Hummingbird (Calypte anna) and even stranger is that they are more common in the winter than the summer – some of them are migrating north when most birds are headed south. We had the luck and privilege of having several Anna’s in Hoonah, Alaska this autumn and winter (2019 – 2020) and that left me with all sorts of questions. Why are the traveling north? What are they feeding on and how do they survive the night? Is this becoming more common? Do the same individuals return every year? Thanks to some inquisitive scientists and their research there are answers to a few of these questions!
Southeast Alaska’s Hummers
Southeast Alaska has a regular hummingbird that shows up each spring. Rufous Hummingbirds (Selasphorus rufus) are everything you would expect a hummingbird to. They are fiesty, beautiful, chatty (with a clicking chat call) and love to feed on flowers and feeders. Their brilliant orange throat is much different than the pink cap of the Anna’s and that makes identifying them easy. Due to that I’m confident that I have not observed Anna’s Hummingbirds at our feeders during the summer in the four years I’ve lived in Hoonah.
In contrast to the Rufous Hummingbirds, Anna’s are a recent addition to Alaska. The first record of an Anna’s Hummingbird in Alaska was in 1971. Until that time they were only found along the west coast of U.S. as documented in Greig et al. 2017. You can see a map of their northward range shift over the last 17 years in their publication. From Ebird you can see Anna’s were scattered throughout the panhandle of Alaska and as far north as Kodiak Island during the winter of 2019-2020.
If you want to know more about caring for and promoting hummingbirds in your backyard in Alaska I recommend this guide from the Forest Service.
Movin’ North, to Alaska
Why move north during the winter to colder climates? It is rare for almost any animal to choose that survival method and it is not typical for any bird that I’m aware of. Could their northward expansion be linked to climate change? Or is there some other factor at play? Emma Greig and a team of scientists published a paper in 2017 to dive into that question. Based on 17 years of data from citizen science, she and her colleagues concluded that feeding (nectar) and urban areas were leading Anna’s to the north in the winter and that it is probably aided by warmer temps – however they conclude that warmer temps alone are not driving the northward shift. Feeders are the key. You can read the full article through the citation below.
Based on Emma’s article I had one follow-up question : why don’t Anna’s stay in Hoonah for the summer? In my four years here I’ve never seen one at my feeders in the summer. To get insight into that I reached out to Emma. She hypothesized that Anna’s were moving away from competition from highly aggressive Rufous Hummingbirds and spreading out to food sources other than feeders in the summer because insects and flowers are abundant. It is also possible they are moving back south. She emphasized there is a lot of complexity in their movement patterns and a lot we do not know.
Surviving the Winter Nights
When you are a small animal (Anna’s weigh up to 0.16 ounces)it is very difficult to survive a cold night. Many species of birds have adapted to cold nights through a biological mechanism called “torpor”. That just means they reduce their body’s rate of energy consumption by reducing their body temperature and lowering their heart rate. No big deal, right? Wrong! Of course it’s a big deal! A 1979 study found that Anna’s hummingbirds gained up to 16.4% of their body mass during the day and that they optimized their feeding and flight to use as little energy as possible (Beuchat et al. 1979). They are storing up all that saved energy so they can make it through the night. As night falls so does their body temperature. Anna’s hummingbirds normally have a temperature of 107F but it may drop to 48F during cold nights to conserve energy. They raise it back to 107 as the day warms up again – talk about amazing!
This winter I saw an amazing record pop up on Ebird that contained an image of an Anna’s Hummingbird in torpor. The image and record was reported by Nat Drumheller in Gustavus (about 25 miles from Hoonah) and I’ve posted his account of the experience above in the caption. It corroborates with behavior changes in torpor and energy efficiency. When this hummingbird wakes up it will be ready for a drink!
Do the same Anna’s Hummingbirds return to Hoonah every winter? That’s impossible to say for certain, but I do have one interesting anecdote. The first time I saw an Anna’s in Hoonah was in 2018. It was a juvenile male and that location is where I photographed the full adult male this year during the Christmas Bird Count (CBC). Seeing as Anna’s can live to be at least 8 years old it is possible that it was the same male. While that doesn’t necessarily count as sound evidence to answer the question it does raise my interest.
Greig and her co-authors concluded with an interesting observation – Anna’s Hummingbirds are an example of humans altering the migration and distribution of a migratory species. Based on that, as the world warms and Alaska’s human population grows I wouldn’t be surprised to see Anna’s as a year-around resident in the future.
Greig EI, Wood EM, Bonter DN. 2017 Winter range expansion of a hummingbird is associated with urbanization and supplementary feeding. Proc. R. Soc. B 284: 20170256. http://dx.doi.org/10.1098/rspb.2017.0256
Carol A. Beuchat, Susan B. Chaplin, and Martin L. Morton, “Ambient Temperature and the Daily Energetics of Two Species of Hummingbirds, Calypte anna and Selasphorus rufus,” Physiological Zoology 52, no. 3 (Jul., 1979): 280-295.