Every evening, just before sunset, the hummingbirds swarm around our feeders. Why do they suddenly get hungry at sunset?
Hummingbirds have one of the highest metabolisms of any animal. This requires them to consume a tremendous amount of food to stay alive. They keep from starving to death each night by going into torpor, a state where their heart rate slows, breathing slows, and and their body temperature drops. It can take a hummingbird as much as 45 minutes to come out of torpor, making them very vulnerable to predators. Torpor will vary with the availability of food. A hummingbird that has enough food will not go into torpor at night, meaning it is much more likely to avoid night time predators.