Baby birds are adorable, helpless, and very, very hungry. They need lots and lots of food because they grow incredibly fast. Their survival depends on it.

How do parents handle the important responsibility of keeping their chicks well nourished? In this edition of Nature Notes, I will share three strategies bird parents use to keep their babies' bellies full - Family Foraging, Stay-at-Home Mom, and Packaged Food. Many bird species use some variation of these three strategies - adapted, of course, to their specific needs. Which strategy they use depends in large part on where their nest is located, whether or not the chicks can leave the nest, how far away the food is, how portable the food is, and how likely it is that other birds would try to steal the food as they return to the nest.

STRATEGY 1: Family Foraging  

Sandhill cranes use what I'll call the "family foraging" strategy for feeding their chicks. The whole family can dine together because sandhill crane nests are on the ground, enabling the chicks to walk right out of the nest to follow their parents around while they hunt for food. They do this within 24 hours of hatching! Staying close together while they are foraging means the parents are always there to protect the chicks against predators.  

Sandhill cranes are opportunistic feeders, and will eat just about anything they can peck out of the ground, such as delicious grubs, worms and bugs. For the first 10 days, the parents will hold food in their own bill and place it directly into the chicks' bills, breaking up any morsels that are too large for the chicks to swallow whole. (Birds are not good about chewing their food - probably because they don't have teeth.) As the chicks get a little older, the parents will drop food at their feet to encourage them to eat more like a grown-up. The chicks become mostly self-sufficient eaters after a month or two, but might still occasionally beg their parents for food until they go off on their own when they are 10 or 11 months old.

STRATEGY 2: Stay-at-Home Mom

Ospreys use the "stay-at-home mom" strategy for feeding their chicks. Because ospreys nest way up high in dead trees, the chicks must eat at home until they learn to fly. Mom stays on the nest with the chicks, protecting them from predators and weather, while the father hunts for food to feed his family.

Ospreys love fish. That's pretty much all they eat. They catch fish by making impressive dives into the water (head and feet first), grabbing the fish in their talons. Still holding onto the fish, they fly back to the nest to show off their catch. The father usually sits on a nearby tree branch and eats the head off the fish, then proudly presents the rest of it to the mother to feed herself and the chicks. Holding the fish in her talons, the mother will rip bits of meat off the fish with her bill and put it right into the chick's mouth. If she thinks a piece is a little too big or firm for the chick to swallow, she will eat that piece herself. After the chicks are about 6 weeks old, the mother will start to make brief trips away from the nest to catch fish, which she drops off at the nest for the chicks to eat on their own. After all that time on the nest, she must be really glad to get out of the house for a while.

The stay-at-home mom approach works well for ospreys because their food is portable, they have great talons that are perfectly suited for carrying fish, and not many pirates would dare try to steal their meal. Further, one good-sized fish is a big enough meal to keep the whole family happy for a few hours, so they don't have to make too many fishing trips.

STRATEGY 3: Packaged Food

Anhinga families rely on the "packaged food" strategy for feeding their chicks. Anhingas nest in trees so the chicks need to eat at home until they can fly. The mother and father take turns foraging and feeding the chicks, while the other one protects the nest. Anhingas are fish lovers, but use very different fishing techniques than ospreys, so they need a different approach to bringing food back to the nest.

Anhingas catch fish by swimming around underwater and spearing fish with their sharp beak. They swallow fish whole, so the fish they catch can't be too big, and they need a bunch of fish to make a satisfying meal. Because they have webbed feet for swimming, they aren't equipped to carry fish around like ospreys do.

So how do they take fish back to the nest to feed the chicks? They swallow them, and store them in their crop. The crop is an enlarged part of a bird's esophagus that serves as a pouch for temporarily storing food. Packaged food! You might notice I used the word "temporarily." Hmmm... How does that work? Regurgitation! Anhinga parents open their mouths nice and wide so the chick can stick its head right in there to eat the food stored in the crop. They do this about six times a day at first, but that's reduced to once a day by the time the chicks are six weeks old. It seems to me this arrangement could only be successful with a really hungry chick and an extremely dedicated parent!

Lots of bird species use regurgitation to feed their chicks because it's both nutritious and efficient. The parent is able to gather up lots of food, then take it to the nest all at once in their crop rather than making many trips with one small bite at a time. And, this approach eliminates the possibility of the food being stolen on the way back to the nest.

One final note: I made up the names of the feeding strategies to help differentiate one from the other. So, if you find yourself in deep conversation with an ornithologist, don't throw that terminology around like you got it out of a textbook. They'll think you're nuts.

DID YOU KNOW?

Chicks have different ways of letting their parents know they are hungry depending on how they are fed. The most common way is for a chick to just open wide and stretch its neck to get its beak as close to the parent's beak as possible. They can be pretty vocal in their begging, too. By instinct, the parent feels a strong stimulus to feed the chick. This works well for birds that put food directly into their chicks' mouths - either by bill-to-bill feeding or by regurgitation. Other chicks use their beak to tap on the parent's beak, stimulating the parent to open wide so the chick can stick its head down the parent's throat to eat whatever is in the crop. Anhinga chicks tell their parents to open wide by pooching out their gular pouch (that featherless bit of skin under the chin), and touching the parent's throat or gular pouch with their beak.

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