5 Facts About Birds That Will Change How You See Them

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By Luis Gustavo. See how we research and review our content.

A tiny logger glued to a common swift can tell a surprising story: for about ten months of every year, the bird barely touches the ground. On the other side of the size scale, a crow in Seattle once kept scolding a rubber mask for five years. Neither fits the idea of birds as “just something in the backyard.”

Behind those two stories sits a lot of real biological engineering, from compasses in the eye to hearts that race past 1,200 beats a minute. Here are 5 facts about the world of birds, plus two extras.

1. Some birds can sleep while flying

The cleanest evidence comes from great frigatebirds. In a 2016 study, researchers fitted 14 of them with tiny brain-wave recorders and let them fly out over the ocean for up to ten days. In the air they slept only about 41 minutes a day, roughly seven percent of what the same birds slept on land, and sometimes with just one brain hemisphere at a time while the other stayed alert.

The common swift is the famous long-haul flier. A Lund University team tracked 13 swifts and found they spent more than 99.5 percent of the non-breeding season airborne, with some birds never landing at all. How swifts sleep up there has not been confirmed; the lead researcher has only suggested they may doze during a long glide, as frigatebirds do.

2. Migratory birds use Earth’s magnetic field as a compass

Studies show many species have a sense called magnetoreception, which lets them “feel” the planet’s magnetic field and use it as a navigation reference during migrations spanning thousands of miles. The leading explanation involves cryptochrome, a light-sensitive protein found in the retina.

In European robins, researchers isolated a version called CRY4 and found its magnetic properties depend on light, a trait that would suit a compass. The same protein from non-migratory chickens and pigeons was less magnetically sensitive. One honest caveat: this was tested in a lab dish, not inside a living eye, so scientists still treat it as a strong candidate rather than a closed case.

3. Not every bird with a beautiful song is easy to spot

Birdsong is often a long-distance communication strategy — it lets birds mark territory and attract mates without needing direct visibility, since many species live hidden in dense vegetation. A voice can carry through foliage where a clear line of sight cannot.

Ornithologists define a song mostly by its job. Audubon’s summary says a song has two main purposes: defending a breeding territory and attracting a mate. Songs tend to be longer and more elaborate, and a singing bird often stays put to broadcast. Calls are simpler and usually go with another behavior, such as raising an alarm or begging for food. Males do most of the singing, though female song turns out to be more widespread than once thought.

4. Hummingbirds have the fastest metabolism among vertebrates

Few animals burn fuel as quickly. At the Smithsonian’s National Zoo, the ruby-throated hummingbird’s heart is described as beating about 225 times per minute at rest and more than 1,200 in flight, while its wings beat roughly 70 times per second. The birds run on nectar, which averages around 26 percent sugar, and add small insects during the breeding season.

To survive nights without food, hummingbirds can enter torpor, a deep sleep-like state that lowers body temperature and slows metabolism. Their normal body temperature is about 105°F, and their feathers insulate poorly, so torpor is a survival tool, not a luxury. Before crossing the Gulf of Mexico, migrating ruby-throats rely on fat stores to fly 18 to 20 hours straight.

5. Crows can recognize human faces

Research shows crows and other corvids can memorize and recognize specific human faces for years, even associating people with positive or negative past experiences. The best-known test used rubber masks. Researchers wearing a “dangerous” caveman mask trapped and banded seven crows, while a Dick Cheney mask served as the neutral control.

Afterward the crows scolded the caveman mask far more, even when it was worn with a hat or upside down, and ignored the neutral one. A follow-up found the scolding was still happening five years later and as far as 1.2 kilometers from the original site. The knowledge appeared to spread to other crows and to their young, which suggests grudges can be passed along.

An 11-day flight with no landing: the bar-tailed godwit

In 2020, a male bar-tailed godwit carrying a satellite tag flew from Alaska to New Zealand in about 11 days, roughly 12,000 kilometers (7,500 miles) without stopping. Strong easterly winds lengthened the trip, and the bird reached a top speed of around 55 mph. Reports suggest it did this without sleeping.

Before leaving, godwits feast on mollusks, crustaceans and worms until their bodies roughly double in size, about half of that gain being fat. Organs that are not needed in the air, such as the stomach and liver, shrink to save weight. It is a reminder that “migration” can mean an engineered, one-shot endurance event.

Reading the numbers on a pair of binoculars

If these stories make you want to watch birds yourself, the two numbers stamped on binoculars are worth decoding. In a model labeled 12×25, the first number means the image is enlarged twelve times and the second is the diameter of each front lens in millimeters. The lens size controls how much light gets in.

The trade-offs are real. Audubon notes that compact models with lenses under 30 mm are light and easy to carry but not bright enough to show detail in poor light, and that higher magnification enlarges hand shake and narrows the field of view, making birds harder to find and follow. Many birders favor 6x to 8x for that reason.

If this topic interests you, it’s worth checking out our piece on penguins and on bats.

Night flyers and ancient relatives are covered too, in our pieces on owls and on dinosaurs.