Hummingbirds live to eat and eat to live. They must. Few creatures exist so precisely at the edge of what could be starvation.8 Yet hummingbirds are protected by adaptations that allow their tiny bodies to survive.
Hummingbird food is a pure source of sugar produced by flowers - called nectar. Hummingbirds usually gather liquid nectars from deep inside long tubular flowers. Dense in calories, there is no richer food source and the hummingbird is dependent upon that very richness.
When hummingbirds gather nectar from flowers, they will not take the nectar if it has less than 12% sweetness. The sweetness is sometimes high or low depending on what kind of flower and how long the nectar has been allowed to accumulate.
This means that hummingbird food (liquid nectar) is sweeter than Coca Cola. The average sugar concentration is 20-25% in 200 of the favorite flowers that hummingbirds like to frequent.10
A heavier concentration of sugar allows the hummingbird to visit fewer flowers. Every time a hummingbird hovers in front of a flower, it uses food (energy) to gather food. It must gather more than it expends to hover and to live throughout the day. The numbers are staggering.
In an average 12 hour day, a 10-gram hummingbird such as the male Anna's hummingbird will need 6,660 calories to live. More than 1/3 of that amount is spent hovering to gather food.12
Each flower yields an average of 0.000035 to 0.0001 ounces of sugar.
One source said that the above Anna's would need to visit over 1,000 flowers to feed itself every day. A second source documented a real hummingbird that probed over 1,300 flowers in ½ a day. A third source claimed a hummingbird will visit 2,000-3,000 flowers per day depending on whether other nectar-gathering insects or birds have depleted the flowers' potency.10
Measured against the weight of the bird, that is a LOT! of hummingbird food.
By comparison, if a human used as much energy as a hummingbird - to run and jump and work all day – that person would need to consume twice their body weight to stay alive. We usually eat between 2 - 2.5 pounds of food in a day and I found that number disturbing for a global ecology.
Imagine 300 lbs. of food per day per person!7
Fortunately, a hummingbird does not consume the flower itself (salad?) so they can come back to feed again as soon as the flower has made more nectar. In some ways they are cultivators and conservationists and remember which flowers have already been harvested.2
Hummingbirds also eat insects. This is called “gleaning,” “gnatting” and “hawking.” Hawking looks like aerial acrobatics made of erratic twists, stops and whirls as they chase invisible bugs.
By invisible I mean that our air is full of life sustaining creatures that feed the hummingbirds and songbirds. In the Midwest, probably above an open field, a sample was taken of one square mile of summer air. Entomologists measured from the ground up to 100 feet high and counted everything.
There were about 45,000 balloon spiders (don't think about it), several hundred thousand tiny thrips, over 800,000 aphids (looking
for new homes) and more fungus gnats than you want to know – about 7 million.
If you are a Midwesterner, then you know there are “peak” insect hours – in the evening when they rise up. During this time the airborne midge population approaches 100 million.
All of this is potential songbird and hummingbird food. We need to rethink the consequence to the food chain when we mass-spray insecticides to kill mosquitoes.10 Dragonflies are called mosquito hawks.1 Everything is interdependent.
Hummingbirds are dependent on small insects and spiders to balance their diet with protein. A dinner of tiny bugs will also substitute for nectar when flowers are scarce or when it rains.10
Some hummingbirds in Costa Rica survive several months of dry season by eating bugs. Anna's, rufous, broad-tailed and ruby-throated hummingbirds also eat tree sap to supplement their diet. They have access to the sap by visiting the holes made by sapsuckers. The ruby-throated hummingbird is dependent on the yellow-bellied sapsucker to provide this food source during it's annual migration.2
Hummingbirds gather and store their food in a small pouch at the base of the throat called a “crop.” Whenever a hummingbird is perching, it is moving food from the crop into the stomach and digesting what it has gathered. Hummingbirds perch or rest nearly 80% of their day but the rest time is still focused toward refueling their small bodies.
Nectars are digested and pass through the hummingbird system in as little time as 10 minutes,12 though accounts vary dramatically from
4 minutes to one hour. One observation showed that nectar was held in the crop for as long as 30-40 minutes before it was passed into the stomach12 and this may account for different points of view. All sources agree it is feasible and necessary for the hummingbird to have immediate energy released into it's system.
Their ability to metabolize nectar is efficient. Nearly 97% of the nectar turns into usable fuel – perhaps the highest use-ratio of any food by any animal. Insect and spider remains have been documented to pass through a white-eared hummingbird in less than 10 minutes.8
Fast and efficient, the hummingbird lives moment to moment on the food it gathers. A hummingbird MUST eat to live but within a narrow margin of survival, there is infinite grace, adaptation and abundance.