Falling asleep after a big meal is commonplace among us humans that over-indulge on festive occasions like Thanksgiving. But I have never seen it happen to a bird until I saw this Downy Woodpecker male fall asleep at a suet feeder. Here is the sequence of action I observed the other day.
Why does food, especially food high in fat, make us (and animals) lethargic? Some say it is the chemicals in the food itself (e.g., the tryptophan in the turkey), and others believe it is the chemicals that the body releases as the food is ingested (e.g., hormones that communicate from the gut to the brain telling it what has been eaten and how much). Either way, the signal the brain receives (indicating satiation) causes a dramatic change in behavior to cease eating and relax.
There is a good reason to relax after a full meal, allowing more blood flow to the gut to absorb the ingested nutrients. It’s the old law of supply and demand. The limited volume of blood needs to go where the demand is highest — in this case, the gut.
But…small birds that go to sleep in plain sight of the abundant natural predators are going to be dead ones, so this is kind of unexpected behavior. Lucky for this bird there weren’t any Cooper’s or Sharp-shinned Hawks in the neighborhood.