The world’s smallest bird can take up a big chunk of a person’s spring to-do list: Trim the trees, weed the garden, make the nectar and hang the feeders.

With the beginning of spring, hummingbirds are making their way north after migrations that took many of them more than 500 miles across the Gulf of Mexico. They will return to the same yards where they have stayed in the past.

“They are fascinating. I call them nature’s miracle. They have all these disadvantages (size, enemies, flying solo), yet they are thriving and have all these incredible abilities,” said John Schaust, chief naturalist for Wild Birds Unlimited Inc. nature shops, which are based in Carmel, Ind.

A hummingbird has to visit between 200 and 1,000 flowers a day to survive, depending on the size of the bird and amount of nectar in the flower, said Ethan J. Temeles, a professor of biology at Amherst College in Massachusetts. Nectar is available in many stores, along with bird feeders, but concoctions can be made at home with four parts water to one part sugar, Schaust said.

Hummingbird numbers are unknown but Schaust estimated it to be in the hundreds of millions, though they are only found in North, Central and South America. They can live between three and five years.

Anyone who wants to attract hummingbirds to their yards should avoid pesticides in their gardens, since the birds need nectar and small bugs, and residue can easily be carried back to its nest, said Monique Rea of San Juan Capistrano, a volunteer hummingbird rehabilitator. Preparing for the return of the birds means carefully trimming trees and plants to avoid agitating a nest, she added.

It might seem like a lot of work for a bird that weighs just a tenth of an ounce, but devotees say the rewards are handsome — among them watching their flight. Hummingbirds flap their wings 20 to 80 times a second in a figure-eight motion to get lift going up and coming down.

They can fly forward, backward, right side up and upside down, making them “one of few birds who can fly backwards and the only one that can sustain flight backwards,” Schaust said.

“It’s just amazing to me that they can beat, breathe, hover and still be able to eat, but they do,” said Hess.

Spring is an ideal time to watch for them, because it coincides with one of the birds’ two mating seasons. Females build walnut-sized nests or redecorate last year’s, Schaust said, in a process that takes six to 10 days. The nests are reinforced with spider web silk, so some homeowners might see the tiny birds in the eaves of homes collecting webs, he said.

To camouflage the nest, the mother covers the outside with lichen from tree trunks and glues it on with tree sap. If a nest breaks before the hummingbirds return, it can be rebuilt by humans.

“Hummingbirds have no sense of smell, so the mother won’t have any problem with you touching the baby. You can even rebuild a nest if it was destroyed,” Rea said.

Emma Eisenhauer, a first-grader at Fremont Elementary School in Columbus, Ohio, knows exactly how small a hummingbird is. For her studies this year, she had to make a life-size model of one — no easy task considering the 6-year-old’s hand was too small to stuff the paper sculpture.

“It had to be bigger than the real bird because otherwise it would be too small to stuff,” she said.