BELLINGHAM - Not so long ago, bird experts advised Whatcom County hummingbird fanciers to take down their feeders at the end of summer, so that the blur-winged little marvels would take the hint and fly south for the winter as nature intended.
No more. Hummingbirds are now as much a part of a Whatcom winter as the dark-eyed juncos that show up by the dozen at every seed feeder. Instead of taking down their sugar-water feeders for the winter, local birders now exchange ideas for keeping those feeders from freezing up when the temperature plunges: String Christmas lights nearby to provide a heat source. Fasten some chemical hand warmers on with duct tape.
What happened? Anna's hummingbird. Until Anna's became established here, the only hummingbird likely to be seen in this area was the rufous hummingbird, and that species cleared out every fall.
As recently as the 1930s, Anna's hummingbird rarely strayed out of California and northern Mexico. But even before humans began hanging up hummingbird feeders, they planted exotic ornamental flowers and trees outside Anna's normal range. The little green bird with the purplish-pink headdress turned out to be one of those lucky species that benefits from human behavior, and they began to expand up the West Coast as they fed on the introduced plants.
According to Cornell University's All About Birds website, the population of Anna's grew by 2 percent per year between 1966 and 2010 as the birds extended their range to the north.
At first, only the occasional adventurous Anna's would pop up on the annual one-day winter bird survey in the Bellingham area, but in the past few years, the local winter population of the bird has exploded. As recently as 2005, local birders tallied exactly one confirmed sighting of an Anna's on their one-day winter survey. In 2010, they counted 21. In 2013, they spotted 52.
Terry Wahl helped launch the first annual local bird survey in 1967 and wrote "Birds of Whatcom County," a comprehensive account of bird sighting records going from the early 20th century to the mid-1990s. Wahl's book is the key source of information on how local bird species populations have changed over the years. The first confirmed Anna's sighting in the county was in 1955, Wahl said.
As Wahl sees it, a variety of factors may be combining to make Whatcom County hospitable for Anna's. He doesn't think human yard plantings and feeders explain everything. The ranges of many species are expanding or contracting in response to climate change, Wahl said.
Wahl thinks the influence of feeders may be overstated.
"I've had reports of birds that are apparently wintering away from feeders," Wahl said.
But the feeders do help to encourage the birds to move in and stay.
"Now that they're known to be around, more people are feeding them," Wahl said.
How do these tiny, energy-intensive birds survive the deep cold snaps of a Whatcom County winter? Unfortunately, not all of them do. During the long cold snap in early December, several local birders reported finding dead hummingbirds, and for several days afterward, the birds seemed to have vanished from central Bellingham.
But within a few days, the shrill twitter of Anna's hummingbirds defending their territories became commonplace again.
Toby Ross, science manager with the Seattle Audubon Society, said at least some of the hummers seem to make it through the cold snaps thanks to an ability to sink quickly into a dormant state when temperatures drop. Their heart rate drops below 40 beats per minute - a steep drop from the astonishing maximum rate of about 1,200 beats per minute when the birds are active.
And all hummingbirds are incredibly active, seeking the calories they need to keep their hearts beating and wings humming. When not feeding, they are often in aerial combat with other hummingbirds, chasing rivals away from food sources.
"The hummingbirds are the feistiest and most aggressive birds we have," Ross said.
Bird experts recommend a blend of one-fourth cup white sugar per cup of water for hummingbird feeders. The solution tends to spoil quickly in warm weather, and needs to be changed every couple of days. Because of its sugar content, the solution will stay liquid a few degrees below the freezing point of plain water, but it is advisable to bring the feeders indoors when nights are cold.
Ross said some people wonder if the man-made calorie source is harmful to the birds, but so far there is no research that documents they are being harmed.
In any event, hummingbirds have a surprisingly varied diet that goes well beyond feeder junk food and flower nectar.
The Cornell website says Anna's hummingbirds also snatch insects from the underside of leaves and gobble up small flying insects on the wing. They even steal bugs from spider webs, and feed on sap oozing from tree holes drilled by industrious sapsuckers.