One of Nature’s Phenomena: Hummingbird Migration

As a naturalist, I tend to be impressed by most natural things – be it a bird, mammal, insect, tree, flower, weed or even a rock. I can’t help but be amazed by its story. I am obsessed with one facet of nature though, and that is the ruby-throated hummingbird. These tiny birds defy logic. They are truly amazing in every possible way!

A humming bird sips on nectar from a coral flower.
A better look at the ruby-throated hummingbird’s iridescent feathers. (Photo: Amy Roell)

To begin with, these diminutive creatures are absolutely gorgeous, with their jewel-toned iridescent feathers, delicate-looking beaks, lightning-quick movements and amazing abilities to hover. Their feathers are iridescent, meaning that they are not actually colored green and the males don’t actually have a red throat. It appears like they do when light passes through the feather because of the way the feathers are structured. If light isn’t passing through or bouncing off in the correct way, you won’t see the green or the red. And it’s only the adult males that have the ruby red throat. Tiny aviators, ruby-throated hummingbirds are between 2.8 and 3.5 inches long, with a wingspan of 3.1 to 4.3 inches. They weigh between 2 and 6 grams. That is the same as a couple of paper clips or a penny!

Ruby-throated hummingbirds are the only species of hummingbird that nest east of the Mississippi River. Their summer breeding range extends from the southern United States northward to mid-Canada. They can be found from the East Coast to the eastern edges of the Great Plains states. They winter in Central and South America. As migratory birds, ruby-throated hummingbirds migrate every spring and fall, most likely when the daylight changes – lengthening in spring and shortening in fall. Males will depart first; females and young leave a few weeks later.

A hummingbird is in mid-flight, eating at a bird feeder.
Even if you leave feeders up in winter, ruby-throated hummingbirds will keep flying by. (Photo: Amy Roell)

Leaving your feeders up will not convince them to stick around. When the internal clock says it is time to go, they leave. But, by leaving your feeders up, you’re providing food for those travelling from places farther north. You can leave your feeders up until early October or when you’re fairly certain you haven’t seen any hummingbirds in several days.

Ruby-throated hummingbirds migrate solo, not in flocks. Even the young born just this summer will make the trip to the wintering grounds on their own – no one shows them the way. (There must be some type of internal map and guidance system setup that they follow.)

In the days leading up to their final departure, ruby-throated hummingbirds will begin to feed more often, starting to pack on extra fat reserves. Scientists have discovered that they can double their weight in just seven to 10 days! When it’s time to go, they will feed heavily in the morning hours and then start off on their journey south. These pint-sized creatures can fly between 45 miles and 60 miles per hour! They will fly for five to six hours before finding a suitable place to feed and rest. To keep up their fat reserves, they continue eating nectar and insects along their journey.

A hummingbird sits on a tree branch. Its wings are outstretched as it shakes off raindrops.
A ruby-throated hummingbird shakes off raindrops after braving a Cincinnati storm. (Photo: Amy Roell)

Since ruby-throated hummingbirds are territorial over their feeding grounds, as they stop along the way, they need to have safe resting spots that can keep them hidden from the other hummingbirds that may feel the particular area is now their territory. Depending on the weather, they may only stay one night or they may stay several nights to ride out a storm or cold temperatures. But eventually, they continue this daily pattern until they reach the Gulf of Mexico. At that point, ruby-throated hummingbirds spend several days bulking up their fat reserves once again, this time for the nonstop flight across the Gulf of Mexico to the Yucatan Peninsula.

At one time, people thought that the hummingbirds would hitch a ride on the backs of geese across the Gulf, thinking there was no way a bird that small could fly 500–600 miles across the ocean by itself. But that is exactly what they do! By putting on an extra 2 grams of fat, ruby-throated hummingbirds can make the over-24-hours, nonstop flight without stopping to rest or eat. They also fly just above the waves, which can be dangerous in and of itself. Once they reach land again, they find a place to rest and feed and then move farther south into Mexico, Panama and Costa Rica.

A hummingbird is in mid-flight, approaching a bird feeder. Its wings are outstretched.
It takes a lot of energy to beat those small wings! (Photo: Amy Roell)

Putting on fat reserves isn’t the only preparation these tiny flyers make for their almost-2,000-mile journey. Their bodies have to transform too. They have to make room for those fat reserves, and the way they do this is to have some of their internal organs shrink. The liver, kidneys, digestive system and reproductive organs shrink to make room for the fat stores. Their heart and chest muscles increase in size and they greatly reduce the amount of sleep time they get.

As these little birds fly, if they need more energy than they have stored up, their bodies will start to consume their own muscles. This is very risky, because if ruby-throated hummingbirds can’t find enough food sources once they land, they may not recover. As they migrate south and over the Gulf of Mexico, they may ‘rest’ in flight by letting half of their brain rest while the other half is awake and alert to avoid predators and hazards like mid-air collisions.

Once they reach their final destination, their bodies must revert back to their previous form as soon as possible. This transformation is more important during the spring migration, as ruby-throated hummingbirds need to reproduce quite quickly. During the fall migration though, there is a bit less pressure on them to revert back to their pre-flight state. In either case, the hummingbirds need to restore between 17–23% of their body weight, protein and water.

A hummingbird is in mid-flight, approaching a coral flower.
(Photo: Amy Roell)

In case you couldn’t already tell, migrating is risky business! These birds have to contend with storms and cold snaps. They have to navigate skyscrapers and other buildings, avoid predators and successfully find food sources along the way. It’s estimated that only 50–75% of the young will make it to adulthood and the average lifespan of a ruby-throated hummingbird is three to five years.

With a little bit of luck (and a lot of skill), the hummingbirds that were born here will return next spring. The males will arrive first. In our area, they may start to arrive as early as the beginning of April. The females will follow a couple of weeks later. The early spring-blooming flowers are just as important as the summer- and fall-blooming ones. And of course, providing clean feeders filled with sugar water is always helpful for the ruby-throated hummingbirds returning to our area and the hummingbirds passing through to and from points farther north.

A hummingbird enjoys nectar from a flower.
In a blink-and-you’ll-miss-it moment, a ruby-throated hummingbird enjoys nectar from a flower in Glenwood Gardens. (Photo: Amy Roell)

If you want to help hummingbirds on their migration journey, fill your feeders with a mixture of one part table sugar to four parts water. Boil the water, stir the sugar in until it is dissolved. Let it cool. Replace every three to four days, unless it is really hot, then replace every other day or when the mixture appears cloudy. Do not add red dye or use any other type of sweetener. The chemicals and other additives can cause problems for the hummingbirds.

I’ll be continuing to provide sugar water until October, then clean my feeders and pack them away until late March when I’ll pull them out and get them ready for the ruby-throated hummingbirds’ return. Until then, I’ll dream about the hummingbirds on their wintering grounds.

Amy Roell
Director of Programming