Anna's hummingbird on a nest at Burnaby Lake.

It always amazes me that such small birds not only overwinter here in Southwestern BC but raise a family in the cold. It wasn't that long ago that snow was on the ground; some mornings still show evidence of frost. How is it possible that these tiny creatures can not only endure the cold, but thrive in it?

Anna's hummers have two speeds. There is the full-throttle speed and the barely-breathing speed. When functioning at full-throttle, the bird's internal temperature sits at a toasty 105°F (that's 6° above our own core temperature). When flying its heart is beating over 1000 times a minute to supply nutrients and oxygen to those flight muscles. They burn about 8 Calories (8000 calories) a day to survive. To put that in perspective, if a human was to eat the same proportion of food in a day needed to sustain a hummingbird, about 300 hamburgers would have to be consumed.

When resting it may go into its barely-breathing mode. It enters a state of torpor. Most hummingbirds are able to enter into torpor; their heart rate, internal temperature, respiration, and energy consumption all reduce significantly. The heart rate reduces to around 50 beats per minute and their respiration reduces to around 6 per minute. Core temperatures drop to somewhere around 40°F. All this means that the bird uses less energy to get through a period of rest. It is estimated that they use approximately 1/7th the reserves they would if not in that suspended low-energy phase.

When in torpor, a hummingbird may appear dead. It is possible they may even hang upside down when in this state. Waking up from torpor isn't all that easy either. It takes from 20 minutes upwards to an hour for them to build their systems up to being fully functional.

We know about the wonderful insulating property of feathers. Birds puff themselves up to trap air and reduce heat loss. Those down pinfeathers help a great deal in the quest for insulation as well. The only problem is that hummingbirds don't have any down feathers. This makes it all the more remarkable. These guys are truly amazing.

Thanks for reading.     Ericspix     Eric Svendsen

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