For migrating birds, fall brings difficulty and danger. To reach warm winter climes, many birds must fly hundreds or thousands of milesbetwinner, expend immense amounts of energy and successfully dodge storms, skyscrapers and other potential threats.

Still, scientists have long assumed that a basic trade-off made migration worth the gamble: Once birds arrived at their wintering grounds, they wouldn’t need to work so hard to stay warm, saving substantial amounts of energy. “But nobody ever tested this,” said Nils Linek, a behavioral ecologist at the Max Planck Institute of Animal Behavior in Germany.

Now, Dr. Linek and his colleagues have done so. Their findings, based on a partially migratory population of German blackbirds, challenge the conventional wisdom. Even in the depths of winter, blackbirds basking in balmy southern Europe or northern Africa did not spend any less energy than those riding out the cold in Germany, the scientists found.

“It’s sort of shocking that there isn’t this net benefit,” said Scott Yanco, an animal ecologist at the University of Michigan and an author of the paper. (Dr. Yanco conducted the research while at Yale University.)

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The study, which was published in Nature Ecology & Evolution on Wednesday, also revealed that the migrants began preparing for their fall journeys several weeks in advance, saving up energy for the flight by slowing their metabolism at night.

How to Become a BirderCard 1 of 5

Start from the basics. Begin with something foundational: Learn to identify a few of the birds most commonly seen near where you live. Digital tools like the Merlin Bird ID app can help. If you spot a bird,  pay attention to things like the size, color, behavior, location and date. Binoculars and field guides might help, but are not necessary to get started.

Pick a time. Any time. Early birders have the best chance of catching a lot of activity, but any time can be a good time to go birding. Even the early afternoon, often considered a challenging time to bird, can be good to spot certain species. Around dusk, many birds become more active again.

Join a group. Connecting with people who share your interest in birds can allow you to break the ice. Try joining a local birding group for an outing, or go birding with at least one new person. You can start close to home, by checking the schedule at nearby parks or nature reserves. Or poke around on social media for upcoming events.

Draw what you see. Try your hand at sketching birds as a way of deepening your observation skills. You can start by drawing a rough circle that will become the bird’s head. Then, add an oval twice the size for the body. From there, you can add details, color and shade.

Listen closely. Many birders rely heavily on their ears to make identifications based on birds’ vocalizations. The Sound ID feature of the free Merlin Bird ID app can offer suggestions for which species are calling or singing around you. Beginners interested in refining this skill may want to tag along with a more experienced auditory birder.

Together, the results suggest that migration is “way more complex than all the theories predicted,” Dr. Linek said. “There were a lot of surprises.”

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