Saturday, January 7, 2017

Anna's Hummingbird: An Unlikely Mountaineer

In my previous post, I talked a little bit about some common winter birds of Sierra Nevada mid-mountain forests.  These are the birds you would expect to see riding out a mid-elevation snow storm: Steller's Jays, Juncos, Flickers and the like.  But let us not overlook one of the tiniest residents of this area, the Anna's Hummingbird (Calypte anna).
You might be aware that hummingbirds are an entirely New World group of birds, and that the vast majority of hummingbird species are found south of California, in Central and South America.  You might even know that we as Californians are privileged with our lovely selection of these little humming jewels; seven species nest in or pass through our state, while the east coast hosts just one species, the Ruby-throated Hummingbird (Archilochus colubris). 
But if you live in lower and mid-elevation areas of the Sierra, or visit developed areas there during the winter, you might be surprised to see these little flying gems persist in gardens and backyard feeders throughout the year.  I was surprised the first time I saw an Anna's Hummingbird at a feeder during a snowstorm several years ago, and I've thought about that little bird ever since.  Just recently, after several people asked me if hummingbirds stay in the mountains year-round, and I answered that they do indeed, I decided it was time to do a little more reading on the subject. 
Taken on January 2, 2017, in a neighborhood at roughly 3,500 feet in the Sierra.
The first thing you must realize is that although little hummers adore our bright red hummingbird feeders, they evolved for countless years without them; they don't actually need them.  Hummingbirds do feed largely on nectar, but they also feed on small insects and spiders to meet their protein requirements.  Those long bills are equally adapted for probing nectar-producing flowers as they are for gleaning tiny arthropods from leaves and bark crevices; they also capture flying insects, and help themselves to insects caught in spider webs or sap.  They feed on the sap itself as well, sucked from holes that have been drilled by woodpeckers and sapsuckers.
Now for the interesting bit, the part I've had a sneaking suspicion about all along.
The original breeding range of Anna's Hummingbird reached across chaparral areas of southern California.  But sometime during the mid-1900's, that range began to extend farther north, as far as the well-watered gardens of British Columbia.  This movement corresponded with urbanization, as well as the widespread planting of an introduced tree species, the popular winter-blooming Eucalyptus.
Hummingbirds absolutely love the fluffy pink flowers of Eucalyptus, which conveniently bloom during the winter when other blooms are scarce.  Traditionally, hummingbird migrations follow the wave of blooms through the season, from south to north, up and down mountain slopes.  But it seems hummingbirds, particularly the largely non-migratory Anna's Hummingbird, has taken to following a new wave of bloom: the wave of blooms that follow newly developed residential areas, with gardens of exotic flowers and those ubiquitous and enticing red feeders.
Male Anna's Hummingbird on a feeder in Turlock.
Traditionally, hummingbirds in southern California have depended on currants, gooseberries and manzanitas of the chaparral, with their long growing seasons and winter flowers.  Now, popular landscape shrubs meet their need for winter blooms with plants such as winter jasmine, sweet box, heather and witch hazel.  Coupled with a few eucalyptus trees and hummingbird feeders, plus all those tasty little insects and woodpeckers to help access sap-filled trees, you have a perfectly suitable hummingbird habitat farther north, and even upslope in the Sierra.
Anna's Hummingbirds have one more handy trick up their sleeves: they can enter a state of torpor.  During severe winter weather and the cold of night, hummingbirds have the ability to essentially go to sleep and wait it out.  When in torpor, a hummingbird drastically lowers its body temperature from between 104 and 107°F to about 48.2°F.  It's respiration rate falls from 245 breaths per minute to just 6, and it's metabolic rate decreases to 300 times lower than when active, saving a massive amount of energy.  This allows Anna's Hummingbirds to spend active winter days feeding on sugar and converting it to fat, then enter into torpor during long, dark winter nights, living off of stored fat until morning.
The photo that started it all.  Taken 6 years ago, the first time I noticed an Anna's Hummingbird in the Sierra
(approximately 3,500 feet in elevation) during the winter - and in a snowstorm to boot!
So while our other hummingbirds - Costa's (Calypte costae), Allen's (Selasphorus sasin), Rufous (S. rufus), Calliope (S. calliope), Broad-tailed (S. platycercus) and Black-chinned (Archilochus alexandri) - are making dangerous migrations south, hardy Anna's Hummingbirds stay behind to capitalize on cultivated gardens, introduced exotic plants, and generous offerings of nectar in specialized feeders.
A note on feeding hummingbirds: The best way to attract hummingbirds and other wildlife to your yard is always to plant flowering California native plants, as well as provide water and shelter.  Nesting sites often include oaks, sycamores and eucalyptus (not native), as well as vines and shrubs such as Ceanothus and manzanitas.  Great information on growing hummingbird gardens can be found on the website of Las Pilitas Nursery or through the California Native Plant Society.  Check out the links!  It's also still okay to provide sugar water in hummingbird feeders, but remember a couple of rules: the ratio always needs to be four parts water to one part sugar, and don't add food coloring!

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