Unless you live on the West Coast, the hummingbirds you know in the warm season likely see waning day length as a signal to head south for the winter. Flying to Mexico or even Central America is a risky undertaking, but the payoff is a plentiful food supply.
In the Pacific Northwest, however, Anna’s Hummingbirds (Calypte anna) are resident year-round. That’s right, they don’t migrate. But they aren’t native, either. They weigh only 0.1 to 0.2 ounces — no heavier than a nickel — but they’re hardy descendants of pioneers who struck out for the north from their traditional range of Baja California, Mexico, to California’s Bay Area. Dates vary, but it’s generally agreed that Anna’s arrived in Oregon and Washington by 1964.
Why, you might wonder, would hummingbirds leave their native habitat of chaparral, oak woodlands and coastal scrub for the Northwest, with its colder winters and shorter season for the flowers they depend upon? The prevailing theory is that they were lured by the planting of blue gum (Eucalyptus globulus) — exotic trees that bloom out of season. Eucalyptus were introduced in the mid-19th century by workers who came to California from Down Under, and had become widespread by the mid-20th century. (Now, they’re considered invasive, and are highly flammable.) Tree tobacco and other ornamental flowering plants were additional enticements. When these tiny birds followed this novel nectar trail, and began showing up in suburban yards, people began setting out sugar-water feeders to help them.
In the warm season, Anna’s eat nectar from flowering plants, as well as insects — which they hawk in mid-air, or glean — including midges, whiteflies and leaf hoppers. One female was found with 32 leafhoppers in her stomach at once. 1
But then comes winter. Sap from sapsuckers’ tree holes and insects attracted to those holes only go so far. It’s then that Anna’s depend on the kindness of strangers (as Blanche DuBois famously said).
Winters in Seattle, where I live, are generally mild, but temperatures can drop into the 20s and even teens, as they did this month (Jan. 12-17). Snow falls some years and can last a week or more. Hummingbirds, being tiny, have a high surface-area-to-volume ratio, so they lose a lot of heat through their skin. That plus their high metabolic rate means they must consume the equivalent of two to three times their body weight every day. (Hummingbirds move sugar through their systems so fast that a human would have to drink the amount of sugar in a can of Coca-Cola every minute to match it.2) And with daylight as short as 8 ½ hours here, they need to eat continually. Also, Anna’s have no down insulation. So what enables them to survive our long, cold nights without food?
Fortunately, they’re equipped with several superpowers. First, their bodies convert the sugar they eat during the day into fat, and store it as fuel for the night. To supplement that fat, they fill their crops before dusk with several long pulls of sugar water.
When they tuck in for the night, they engage their next superpower: Entering torpor, a form of deep sleep. In torpor, they lower their body temperature from a hot 107 degrees to about 48 degrees. This is a warm-blooded creature, mind you. There’s more: In daytime, their heart rate ranges from around 400 to 500 beats per minute, while at rest, to a blistering 1,260 beats per minute when in flight. At night? It plummets as low as 50. Also, respiration slows dramatically. All in all, they can lower their metabolic rate by 95 percent.
That takes care of fuel, but the Anna’s still must stay warm. For that, they employ their next superpowers — fluffing their contour feathers to trap warm air and reduce caloric need (called piloerection), and shivering. They don’t shiver by shaking, the way we humans do. Instead, they rapidly contract opposing muscle groups. These strategies enable them to use 50 times less energy until the sun rises and they can power down a quick energy drink of sugar water.
I’ve been watching Anna’s in our garden for 34 years and will share some of my observations here. (Note: I delight in getting to know birds as individuals. To keep track of their differing behavioral traits, I name them.) My first observation is that Anna’s are pugilistic, even during fierce cold. You’d think they’d share, but you’d be wrong most of the time — in our garden, anyway. Here, each hummingbird guards its own feeder and is largely averse to sharing. When subfreezing temperatures hit, to prevent fights, I set out extra feeders for Anna’s visiting from other yards. (Not all neighbors with feeders are able to swap them during the day when they freeze, or set out heated feeders.)
Despite people’s best efforts when cold is severe, some Anna’s don’t make it. During our recent bout of subfreezing temperatures, OceanDiver and RonK — both of whom live north of me, where it was even colder — reported finding dead Anna’s.
Anna’s can encounter other problems besides not being able to find a feeder. The following story arose from the opposite situation. At our house, in February of 2021, a multi-day snowstorm hit, and temperatures stayed persistently low. Mr. Flashy, a magnificent male Anna’s, had reigned over an area with a feeder near our large Salvia garden since summer. He was highly excitable, and during this cold weather was fighting off all interlopers. I felt sorry for the hungry Anna’s trying to stay alive, and set out two extra feeders, at different angles and at a good distance from Mr. Flashy’s. So what did he do? He explored different perches until he found a vantage from which he had all three feeders in his sight-lines.
Snow was high — nine inches had fallen on Feb. 13th alone, and we got more than a foot total that week — and the day was cold, but Mr. Flashy insisted on guarding all three feeders. Repeatedly, he raced from one to another, fighting off any hapless hummer who dared try to feed at one. Anything in his territory was his, get lost.
Apparently, he expended so much energy fighting that day that he didn’t have enough fuel to burn through the night. He’d lived daily in our garden for many months, but we never saw him again after that day.
* * *
For a behavioral contrast, let’s back up more than a week to Feb. 7, the day before that long snowstorm began. All the birds in our garden seemed to sense the coming change in the weather, and searched frantically for food. Mr. Foxhole, a male Anna’s who held territory just on the other side of the house from Mr. Flashy’s, reigned over the choicest cold-season spot, with an autumn-blooming Camellia sasanqua and a feeder hanging from one of two winter-blooming Mahonias (see photo, below). Unlike Mr. Flashy, Mr. Foxhole was tolerant of — dare I say, welcoming to — fellow hungry hummers. Here’s a photo of an unprecedented event in the history of our garden, four Anna’s feeding peaceably at one feeder:
I’ve seen several photos of Anna’s sharing a feeder during cold weather, but in our garden, Mr. Foxhole was the rare tolerant male hummingbird.
Sometimes even superpowers and human help aren’t enough for an Anna’s in inclement weather. On a cold, snowy morning in 2010, Mr. WordsandBirds looked out onto our porch in the dim light and saw something odd, which he said looked like a piece of coal. He picked it up and held what appeared to be a frozen male Anna’s, a bird that hadn’t been able to summon sufficient energy to emerge from torpor and fly toward food. We settled him into a perforated shoebox lined with a heating pad topped with a thin towel, turned the heat to warm, covered the box and waited.
And waited. We checked him every half-hour. For hours. When finally he moved slightly, we took turns warming him in our hands and dipping his bill into a feeder port to encourage him to eat. But he could barely move his tongue. The day was very dark, and daylight was growing short. We kept it up.
At last, five hours later, he got wiggly, and we released him onto a feeder on the front porch. He took a few sips. Suddenly, wham! Another male Anna’s flew right at him, knocking him off. We saw him dive into the bushes, but he didn’t return — to that feeder, anyway. We’re confident that he survived, though. During the next couple of weeks, a male Anna’s flew near each of us and checked us out repeatedly. Only juveniles had done that before. This bird seemed to sense something familiar about us, perhaps our voices.
If you have Anna’s in your area, here are some plants that they favor: Our cold-season magnet is a non-native Mahonia. At Seattle’s Washington Park Arboretum, in the late 1990s, I watched a dozen Anna’s feeding on the delicate yellow blossoms of Mahonia x media ‘Arthur Menzies’ — in January — and I knew I had to have that plant. Mr. WordsandBirds found a hardier cultivar, Mahonia x media ‘Charity.’ It blooms from October through January. A feeder hangs from one of those bushes. That was Mr. Foxhole’s winter hideout.
In spring and summer, our Anna’s enjoy the pink blossoms of Flowering Currant (Ribes sanguineum). After that they can choose here from dozens of Salvia species, various hardy fuchsias, columbines and penstemons and Abelias.
Anna’s form no pair bond, but the courting male puts on a spectacular performance. It’s the most elaborate of any North American hummingbird. From as high as 130 feet, he plunges toward his intended, emitting a sharp, piercing sound from his tail feathers at the bottom of his dive — loud enough to reach the ears of distant females. (The drop is “the highest known length-specific velocity attained by any vertebrate,” and his average speed is twice what has been reported in Peregrine Falcons! 3) He then pulls up and ascends, hovering just above the female. Males have been documented making as many as 40 of these J-shaped dives for the benefit of one female. (That’s if she sticks around for the whole show; some females apparently aren’t impressed.) I’ve watched display this many times. The female sways her head, intently tracing the male’s trajectory. She doesn’t miss a move, and appears transfixed — as though thinking, “All this is for me?”
If the female is dazzled by his speed and flashes of color, she leads him to a secluded site and perches. “The male then performs a shuttle display, where he swings back and forth about a foot above the female, keeping his body horizontal and his head down toward the female, often singing an intense song.” 4 I’ve seen this too. It’s as though he’s a snake charmer, or a hypnotist. After winning his lady, they mate (I have not seen this), and then he flies off to seek other partners; he’s a mere sperm donor. (Females are thought to have multiple partners as well.) It’s roses for her, but nothing later. She’ll build a nest, lay two eggs and do the work of rearing the chicks by herself. That amazes me, because an Anna’s must work much of the day to feed itself. Being responsible for two more mouths seems daunting. And nesting can begin as early as February or even mid-January in the Seattle area.5 Also, while nesting, a female must give up one of her superpowers: She does not enter torpor. I presume her nest and, eventually, nestlings, help to keep her warm. And fortunately, she’s a skillful hunter. A nesting female can capture as many as 2,000 insects a day.
This love ‘em and leave ‘em approach may seem strange, but it’s effective: Between 1966 and 2019, the total population of Anna’s increased 2 percent per year. Partners in Flight estimates the total breeding population at 9.6 million. During the 2023 Christmas Bird Count in Seattle, 705 Anna’s were seen.
“This species’ effective use of widely cultivated urban and suburban exotic plants and hummingbird feeders has contributed to its increased numbers and expanded range,” says Birds of the World. In other words, they’ve put us to work for them. (Note: Some Anna’s in California migrate to higher elevations after breeding season for better food selection, But that’s another story.)
Here are the Anna’s living in our garden this winter:
The bird who owns the front-yard feeder is camera-shy, and the trees conceal her (at least I think it’s a female) so well that I haven’t been able to get a photograph yet. If it’s a female, she’ll soon be nesting.
In spring, young Anna’s will appear again in our garden, mostly gray and openly curious about us.
1, 4 CelebrateUrbanBirds.org, Cornell University
3 Proceedings of the Royal Society, Biological Sciences (2009).
5 Birds of the World
Most of the research for this diary is from Birds of the World (subscription required), with additional information from Kenn and Kimberly Kaufman in Birds and Blooms, All About Birds, earthlife.net and wildlifeinwinter.com.
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