Back in October, I wrote a post about the Anna’s Hummingbird that was hanging around in my backyard. It was king of the hummingbird feeder back then but I wondered if it would stick around through the cold winter months.
As these recent photos show, the little hummer is still with us. It perches on the same branches every day and chases off any other hummingbirds that come to drink from the feeder.
This bird has charmed me and my wife. We are amazed that it keeps going about its business even on the coldest, wettest days.
But of course, it has no choice but to remain vigorously active. A hummingbird must drink flower nectar (or sugar water) and eat insects continually to fuel its high metabolism. A turbo-charged metabolism is needed to power the flight muscles that work so hard and fast in hummingbirds. No other vertebrate animals have such high metabolisms.
Due to their tiny body sizes and lack of downy feathers, hummingbirds lose body heat rapidly. A hummingbird can die within a few hours due to starvation or hypothermia if it does not eat. This is especially true during winter at higher latitudes. Most North American hummingbirds fly south to warmer climates for the winter. Anna’s Hummingbird is an exception.
Hummingbirds and many other small birds have a physiological adaptation that allows them to survive through the night, when they do not feed and when the air temperature drops. These birds enter a state called torpor, in which their metabolisms (and thus, their body temperatures) are dramatically lowered. In a state of torpor, a bird burns far fewer calories that when it is active. Torpor is like hibernation, except that it occurs on a daily, rather than annual, cycle.
In addition to lowering their metabolisms when they are unable to feed, hummingbirds combat the cold by fluffing up their feathers. This increases the amount of dead air space trapped in the feathers and increases their insulating power. Our little backyard hummer demonstrates this feather fluffing in the photo at the top of this post. Fluffing is not unique to hummingbirds– as far as I know, most (if not all) birds do this.
Hummingbirds are truly fascinating animals. I am honored to have one residing in my backyard. I hope that it stays through the spring and summer. If it does, you can expect more blog post updates!