Anna’s Hummingbirds and Torpor

Anna's Hummingbird (female) by Hayley Crews

Did you know that the Portland area is the year-round residence of one species of hummingbird? Anna’s Hummingbirds, the largest of coastal Pacific Northwest hummers, are nonmigratory. How do these tiny little birds, so dependent on nectar and insects for food, manage survive this far north? They, like other hummingbirds, have the ability to go into a torpid state to conserve energy.

The fast metabolism of Anna’s Hummingbirds bird requires large quantities of fuel.  Deprive a hummingbird of food for even a couple of hours at the wrong time and it will will starve.  To get through a mild night, a hummingbird merely sits still to conserve energy.  But if this doesn’t cut heat loss sufficiently, the torpor mechanism takes over and drops the bird’s temperature from 105 degrees Fahrenheit to within several degrees of the surrounding air.  Its heart rate slows to 40 beats per minute, a drastic cutback from 500 per minute on idle and 1200 during flight.  In the morning the system revs up again, but doesn’t achieve full recovery until the bird can take flight.

Anna’s Hummingbirds will readily visit a sugar-water “nectar” feeder, even more so in the winter months when less naturally occuring nectar is available.  We hear wonderful stories from customers and coworkers alike about their wintering hummingbirds, and the fun and fascination of helping these marvelous flying machines through the bleak days of winter.