Thousands watched online as American bald eagles Harriet and her mate, M15, welcomed their first eaglet on New Year’s Eve, nearly two days after the chick began to hatch.

The eaglet, named E9, or eaglet 9, broke through its shell at 7:33 a.m. ET, according to the real estate company hosting the online live-stream. The new parents fed their latest addition throughout the day, and continued to incubate the second egg, which has yet to hatch.

The first eaglet broke free of its shell early Saturday.

But just how hard is it for baby eagles to survive in the wild?

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According to the U.S. Fish and Wildlife Service, though eagles are natural predators, the mortality rate during their first year of life is greater than 50 percent.

Occasionally, eaglets are killed in the nest by other eagles fighting over territory, and in rare instances owls can prey on the chicks. Eagles can also crush their eggs if startled or if they step on them accidentally, but they generally take care when entering and exiting the nest.

But it's man-made hazards, including lead poisoning, that continue to pose a significant threat to the U.S. eagle population, according to the National Eagle Center. Eagles are carrion birds and often ingest lead by eating bullet fragments or contaminated fish. Even the smallest amounts of lead can damage birds' nervous systems and cause organ failure, potentially killing eagles within days, the center warned.

After the eaglets hatch, both parents take turns caring for their newest additions. Male eagles typically spend most of their time hunting and defending the nest, while females feed the new chicks by offering them small strips of fish, which they swallow whole, according to the Center for Conservation Biology.

The largest eaglet usually gets the most food, and when food is scarce, the chicks sometimes fight to establish dominance, according to the conservation. This is to ensure that the strongest eagle survives.

Related: Eagle Cam Watch: First of Two Eaglets Hatches in Florida

Bald eagles are usually read to fledge — or fly for the first time — by 9 to 10 weeks of age, the wildlife service said. By then, they are close to being full grown and can weigh as much as their parents.

After weeks of strengthening their wings by flapping, young eagles typically make their first flight by gliding to a nearby tree or branch. Eaglets that are reluctant to fly are sometimes forced from the nest by their parents. But even after they learn to fly, eaglets continue to depend on their parents for food.

As they grow and their flying improves, chicks begin to harass their parents by stealing food from them. This helps them learn how to hunt and become more independent. After about six months in the nest, the wildlife service says the bonds between baby eagles and their parents begin to fade and the eaglets — now fully grown — strike out on their own in search of their own territory and feeding grounds.