For my final post from Ladysmith, I’m going off-script and away from the regularly scheduled program. That is, I said I would write about the log-boats and the American dipper, but those will have to wait for another post. Instead, as we prepare to say goodbye to our wonderful home for the past 6 weeks, I’d like to make a long-overdue introduction—to the Anna’s hummingbird. Those of you on the west coast will almost certainly be familiar with this emerald and magenta bedazzled whirlwind of a bird. Anna’s breed from Baja California, Mexico to southern British Columbia, and are common backyard inhabitants across that range. Amazingly, these hummingbirds used to breed only in Baja and southern California, but beginning in the latter half of the 20th century, they expanded their range northward as non-native flowering plants and hummingbird feeders increased on the landscape. This dramatic, and rapid range expansion provides an interesting case study regarding the question of what sets the limits on a species’ range. For the Anna’s hummingbird, reliable sources of nectar seemed to be the historical limiting factor regarding the northern edge of their range boundary.
But now that non-native flowering plants and hummingbird feeders are pervasive, what factors determine that northern edge? Is it competition with other species like the Rufous hummingbird, which breeds all the way up to southern Alaska? Is there a parasite or pathogen that limits the northward expansion? One clue to this question may be related to the fact that Anna’s typically are non-migratory. This means that the area they breed in is also the area they winter in. It’s entirely possible that the current cap on the Anna’s range is their ability to deal with cold winter temperatures. But whether this limit is determined by the Anna’s ability to cope physiologically with cold temperatures, or because all the nectar is frozen, is not clear.
Anna’s hummingbirds, and hummingbirds in general, are marvels of energetic performance. They can flap their wings 70 times a second, can fly at speeds up to 50 mph, and their heart rate can exceed 1200 beats per minute. These feats require large inputs of energy, which is where the sugar rich nectar comes in. But how do Anna’s keep their internal engines fueled during the winter when they are unable to feed for the 14 or 16 hours of darkness? Hummingbirds, including the Anna’s, have some amazing tricks in their physiological tool-belt, and one is that they can go into a state of suspended animation each night. This is called torpor, during which the birds slow their metabolic activity and decrease their body temperature from 107 F (41.7C) to about 48 F (8.9C). This daily thermal transition is probably unparalleled in the animal kingdom (although some bats that go into torpor may come close), and allows the hummingbirds to conserve huge amounts of energy during the night. In the morning, the little birds slowly re-enter their normal state of awareness and activity; think caffeine-addicted humans before their first cup of coffee.
Once a bird’s mental and physical abilities have fully returned, it will zoom off in search of a meal. Nectar from flowers and feeders isn’t their only source of food. Anna’s will happily consume insects and spiders (if they are available), and they may engage in a little thievery from another winter resident: the red-breasted sapsucker. Members of the woodpecker family, sapsuckers are so named because of their foraging preference: tree sap. Sapsuckers are like maple-syrup farmers; they tap into a tree’s transport system, and harvest the xylem and phloem that oozes out. A sapsucker usually creates a neat, rectangular grid of holes which it expands over time. An individual will generally have a number of active trees that it’s harvesting from, so it moves about from tree to tree, tending the sap-production facilities and ensuring that no sap thieves steal its hard-earned food. Unfortunately for the sapsucker, hummingbirds have a taste for sap too, and will stealthily zip in to lap up some of the goods when the woodpecker is away.
Once fueled up, Anna’s can get back to their hyperactive ways, chasing each other around and performing their astounding aerial displays. To impress a female, or to intimidate a rival male or other intruder (including hawks, ravens, cats, and humans), a resident male will hover in front of the target, flashing his brilliant pink gorget, and then climb straight up like a helicopter as high as 130 feet in the air. Once the male has reached the zenith of its ascent, it plummets down to the female or intruder, and then swoops up to create a J-shaped dive. At the bottom of its dive, the male Anna’s spreads out his tail feathers, which create a high-pitched squeak as the air passes over them at high speeds. This sound had been attributed to the hummingbird vocalizing, but Chris Clarke, now faculty at UC Riverside, discovered that it was the tail feathers that were responsible for creating the squeak. He has since demonstrated that a number of hummingbird species create sounds using their feathers as part of their displays.
The male Anna's hummingbird has a magenta-colored gorget, which extends up onto the forehead. This color is a product of the microstructure of the feathers rather than pigments, which means that they only reflect this electric pink color when the light hits them just right. Cowichan Estuary, Duncan, BC.
Anna’s hummingbirds are ubiquitous here on southern Vancouver Island, and have relatively early breeding periods. About a month ago (prior to the prolonged cold and snow we received), I saw a female carrying nesting materials; fur from a cattail head. My suspicion is that her nesting attempt either failed or was put on hold for the duration of the coldsnap, but who knows. I wouldn’t have thought these birds could survive numerous consecutive days with temperatures dropping into the teens at night, and daytime highs in the 20s, but they managed it. And now the males are back to their energy-wasting displays and chases, and I suspect the females are back to nesting, or preparing to nest. Given the way in which these birds handled the recent inclement weather, I wouldn’t be surprised if their expansion northward continues, and these little flying gems are soon common up and down the BC coast.
Otter update: In an early post about the resident river otters (post 4—“The New Neighbors”), I mentioned that the local seabirds liked to keep a safe distance from the otters. I described an incident involving a common loon, in which I suspected the otter of attempting to steal the loon’s meal, and also how a group of otters at Marin Headlands in California had become duck and gull specialists. But as far as I knew, the otters here weren’t bird hunters. That has changed. The other day I ran into Steve (one of the wonderful landlords, who, along with his wife Susan, have been so welcoming to us), who told me that he saw an otter dispatching a large bird in the water. After looking at some pictures he took, I determined that the bird was a common loon. This information changes my view of the incident I saw 5 weeks ago. Now I suspect that the loon was not the target of kleptoparasitism (a fancy word for food thievery---something my wife often accuses me of), but was itself the target, and the action I saw was its mad dash to freedom. It shouldn’t be surprising that the otters here would exhibit this behavior, but if I had the choice of crab or poultry, I know which one I would choose. It is entirely possible, however, that I would feel otherwise if I ate 10-20 crabs a day for weeks on end; everybody likes a little variety in their life.
And on that note, we are off to Quadra Island today.
Next post: TBD
About the author:
Loren grew up in the wilds of Boston, Massachusetts, and honed his natural history skills in the urban backyard. He attended Cornell University for his undergraduate degree in Natural Resources, and received his PhD in Ecology from the University of California, Santa Barbara. He has traveled extensively, and in the past few years has developed an affliction for wildlife photography.