Adam Rose Fans

Bald eagles build the largest tree nests of any bird in North America, and some become true giants over time.

Instead of starting from scratch each breeding season, a mated pair usually returns to the same nest year after year, adding fresh sticks, branches, moss, grass, and other materials.

Decades of constant repairs can turn a modest nest into a massive structure several meters across and weighing close to a ton.

The largest reliably recorded bald eagle nest measured about 9.5 feet (2.9 meters) across, 20 feet (6 meters) deep, and weighed an estimated 2,700 pounds (over 1,200 kilograms).

These enormous nests are typically built high in sturdy trees near lakes, rivers, or coastlines, where the birds have easy access to fish.

Such huge nests provide a stable platform for raising one to three chicks each year and are strong enough to withstand harsh weather.

Crows have exceptional memories and can recognize individual human faces for years.

If a person captures, injures, or repeatedly threatens a crow, the bird may begin scolding or dive-bombing that person whenever it sees them.

Even more surprisingly, other crows can learn to identify the same individual by watching the bird's reaction or through social learning.

Young crows observe their parents and other adults closely.

If the adults consistently alarm-call at a particular person, the youngsters can learn that the individual is a potential threat without ever having a bad experience themselves.

Researchers have even found that this knowledge can spread through local crow populations and persist for many years as new generations learn from older birds.