Why do baby guillemots jump off cliffs before they can even fly?

For any young seabird, growing up means eventually trading the safety of the nest for the abundant food waiting out there in the big, scary world. It's a tough transition, but at least most birds wait until they can fly.

Not guillemot chicks, though! They waddle to the edge of a cliff only three weeks after hatching, spread their still-growing wings, and with some urging from mom, plummet their way into the world, aiming for the Arctic seas below.

Scientists have long wondered why these little "jumplings" take such a dangerous leap. The frantic flapping of the chicks' underdeveloped wings can slow their descent, but can't protect them from the dangers of lurking predators or an unfortunate crash into sharp rocks. Even the chicks who successfully make it down aren't great at landing, instead ending their fall by bouncing hilariously like a fumbled football.

All things considered, wouldn't it just be better to wait until they can actually fly?

An international team of Arctic researchers suspected the answer may lie in the behaviour of mom and dad. To find out, they attached electronic loggers to the legs of several adult guillemots on Saunders Island in Greenland to record information about their flight and feeding.

Guillemots, also called murres, live all across the world's northernmost seas. Most of their lives are spent out on the water, where they hunt fish, squid and other tasty seafood by diving as deep as 200 metres (650 feet) beneath the waves.

In the springtime, the birds take to land, congregating on sea cliffs in breeding colonies that can number in the hundreds of thousands. Males and females take turns guarding their one yearly baby and flying to the sea to bring back food. When summer comes, the chicks make their death-defying premature jump, and join dad in the sea, where they live together for several more weeks.

The new study, published in The American Naturalist journal, revealed a surprise about what happens next. Previously, scientists thought that leaving the nest put the chicks in significantly more danger, but this research found that chick mortality at sea was similar to mortality back at the colony. But while leaving home didn't affect the birds' safety much, it did have a big impact on how much the birds got to eat.

"Our measurements show that the male feeds the chick twice as much as both parents could if the chick remained in the colony," says Morten Frederiksen of Aarhus University in Denmark. "At sea, the male does not need to spend time and strength on flying back with food, but can just dive for it."

This revelation showed that for the guillemot chicks, leaving the nest wasn't so much a trade-off – less safety for more food – but really just an opportunity for more food and faster growth!

"This explains why the chicks leave the colony so early," Frederiksen adds. "The faster growth at sea ensures survival of the population." He and his colleagues suspect the chicks are ready to leave the nest as soon as their wings are big enough for them to "parachute" down to the water.

This situation is great for the chicks, but it's rough on dad. The study showed that guillemot fathers watching their chicks at sea spend a lot more time diving for food each day compared to mom (she's back at the colony, defending her nesting spot – and maybe getting friendly with other males, just in case her mate doesn't come back next season).

What's more, dad generally finds himself hunting in areas with much less available food. "This is because the males swim with the chick and therefore cannot fly to the best feeding areas," Frederiksen explains.

So, why do baby guillemots jump off cliffs? Because they have hard-working fathers who ensure they stay safe and well fed, allowing them to grow up and learn what it's like to support chicks of their own!

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Top header image: Rolf Maibaum/Flickr