I watched this red-bellied woodpecker (see image below) the other day, when the temperature was below zero, and I wondered how many trips it made to find enough food for it to survive one day. So I went online.
"On average, birds eat approximately 1/2 to 1/4 of their body weight every day. For example, a 2 lb. cardinal, a seed-eating bird, would consume approximately 1/2 to 1 lb. of seeds per day. While precisely how much seed is eaten varies by species, birds eat more in the winter than in the summer due to metabolic needs. For example, a sparrow can only survive 15 hours without food in 5 degree Fahrenheit conditions, but three days in warm summer conditions."
When I got home I immediately refilled my bird feeders.