A great blue heron talks about food

Food is a big deal to birds. Birds are always busy doing something, like hunting for prey, avoiding becoming prey themselves, taking care of chicks, or migrating. They also need to be revved up so they can take flight at a moment's notice. To support all this activity, birds maintain a high metabolic rate. That means they need lots and lots of food. Foraging is practically a full-time job for many birds, so when faced with the challenge of eating a particularly big meal, they aren't going to give up easily.

Introducing Harry the Heron. My husband discovered him in the back yard one day struggling with a big fish. We don't know how he caught it, but if he was like most great blue herons, he patiently waited for the fish to swim into range, then used his beak to either stab it or grab it. Harry did, however, give us some good insight into how he eats and digests meals like this.

Introducing Harry the Heron. My husband discovered him in the back yard one day struggling with a big fish. We don't know how he caught it, but if he was like most great blue herons, he patiently waited for the fish to swim into range, then used his beak to either stab it or grab it. Harry did, however, give us some good insight into how he eats and digests meals like this.

I recently had the opportunity to interview a great blue heron about his eating practices. I was hoping he would have some helpful hints I could put to use the next time I go to a buffet or sit down to Thanksgiving dinner. I learned some very interesting things that made me realize I could never hope to keep up with a great blue heron when it comes to eating and digestion.

First of all, Harry the Heron explained that he is an opportunistic eater who is a devotee of the "eat local" movement. He'll eat pretty much anything that can be found in abundance nearby, including frogs, snakes, lizards, mammals, and birds. But his favorite food by far is fish. He isn't shy about catching some sizeable prey, and that can present some real logistical challenges. First of all, birds don't have teeth, so they can't chew up the fish or bite it into smaller pieces. They have to swallow it whole. Second, as you have probably noticed, birds don't have hands, so they have to find creative ways to get the fish properly positioned for swallowing. This is very important. Great blue herons have even been known to choke to death while attempting to swallow a big fish.

As Harry the Heron struggled to swallow his dinner, he passed along the following advice for eating a large fish:

Position the fish to go down your throat head first. This is critical as it will prevent the scales and fins from getting stuck in your throat.

Position the fish to go down your throat head first. This is critical as it will prevent the scales and fins from getting stuck in your throat.

If you can't get the fish in perfect position the first time, give it a little flip to reposition it. This may be hard to do if you don't have hands, so there's a risk you could drop your dinner.

If you can't get the fish in perfect position the first time, give it a little flip to reposition it. This may be hard to do if you don't have hands, so there's a risk you could drop your dinner.

If you do happen to drop it, quickly pull it out of the water again. It probably can't swim away at this point, but keep a watchful eye out for other birds that might want to steal your fish.

If you do happen to drop it, quickly pull it out of the water again. It probably can't swim away at this point, but keep a watchful eye out for other birds that might want to steal your fish.

Try again to position it to go down the hatch. Don't be alarmed if the fish is looking back at you.

Try again to position it to go down the hatch. Don't be alarmed if the fish is looking back at you.

Use your tongue and jiggle your head to get the head of the fish aimed down your throat - again.

Use your tongue and jiggle your head to get the head of the fish aimed down your throat - again.

If it won't go, try using the bottom of the pond as a pushing aid.

If it won't go, try using the bottom of the pond as a pushing aid.

FYI, if the bottom of the pond is too mushy, you could end up with a muddy fish.

FYI, if the bottom of the pond is too mushy, you could end up with a muddy fish.

If that happens, rinse the fish off. Keeping it clean and slippery will help it slide down your throat. Don't worry about a little sand, though. That can be good for your gizzard.

If that happens, rinse the fish off. Keeping it clean and slippery will help it slide down your throat. Don't worry about a little sand, though. That can be good for your gizzard.

Give the fish another flip to position it properly. Don't feel bad if you have to keep trying this over and over. Practice makes perfect. Having hands would really help.

Give the fish another flip to position it properly. Don't feel bad if you have to keep trying this over and over. Practice makes perfect. Having hands would really help.

Throw your head back and hope that gravity will help the fish go down your throat.

Throw your head back and hope that gravity will help the fish go down your throat.

Keep at it. Don't give up. Swallowing the fish you have is easier than catching another one.

Keep at it. Don't give up. Swallowing the fish you have is easier than catching another one.

Eventually it will start to go down your throat. By the way, don't worry if you get some algae stuck on your beak. It's a little embarrassing, but unavoidable.

Eventually it will start to go down your throat. By the way, don't worry if you get some algae stuck on your beak. It's a little embarrassing, but unavoidable.

Once it's in there, keep your beak tightly closed so the fish can't pop back out. You might have an uncomfortable lump in your throat, but it's worth it. What a meal!

Once it's in there, keep your beak tightly closed so the fish can't pop back out. You might have an uncomfortable lump in your throat, but it's worth it. What a meal!

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Once Harry finally managed to swallow the fish (after a long twenty minutes), he explained that digestion is a very important part of this story. Birds need to get quick energy from their food, while minimizing the amount of time a heavy meal weighs them down. Taking to the air with a huge, undigested fish in your stomach is no easy task - and a slow takeoff could put a bird at risk from predators.

Fortunately, birds are digestive wonders! Harry gave me an informative rundown on digestion in birds, which is similar to digestion in humans - with some notable and interesting differences.

Let's start at the top and work our way down. Once a bird has used its bill and tongue to guide its meal into its mouth, the food goes down the esophagus - a relatively straight, muscular tube (like humans). This tube can stretch a lot, which helped Harry swallow that big fish without choking (unlike humans).

The first stop on our digestive journey is the crop - a sack-like widening of the esophagus where birds can store food temporarily (unlike humans). This enables birds to eat quickly and move to a safer place to digest in peace. Or, it's a convenient way to carry food back to the nest for feeding chicks.

Once the food goes beyond the crop, it ends up in the stomach. A bird's stomach has two parts (unlike humans). The first part is called the proventriculus, and this is where stomach acids and enzymes break down the proteins in the food (like humans). The second part of the stomach is the gizzard. The gizzard has strong, muscular walls that contract to mechanically grind up the food. This is important since birds swallow their food whole. Some birds even swallow sand or stones to help the gizzard's grinding action. (Humans don't need a gizzard since we have teeth to grind up our food.) Any undigestible bits (such as fur, teeth, feathers, insect exoskeletons) form pellets in the gizzard, which birds regurgitate after digesting the good parts. Birds regurgitate on purpose (unlike humans).

Cruising right along, the food then makes its way into the small intestine. (The diameter is small, but this is actually the longest part of the digestive tract.) The small intestine is where the super cool biochemical stuff happens (like humans). Bile from the liver splits fats into tiny particles and neutralizes acids from the stomach. Insulin and other enzymes from the pancreas break down proteins and the tiny fat particles into nutrients, which are then absorbed into the bloodstream.

Any waste products that are left at this point move into the large intestine, where water is reabsorbed and feces are formed (like humans). The final stop in the journey is the cloaca (unlike humans), where the feces are stored temporarily. About this time, birds are starting to look for a nice clean car to target. The cloaca also receives uric acid from the kidneys in the form of a thick white liquid. That's why, when birds decide to lighten their load, we see the familiar white droppings with a bit of dark solid stuff in it. How efficient! It all comes out at once.

In humans, digestion is a 24-72 hour process. Most birds, including great blue herons, can get food in one end and out the other in just a couple of hours - or less. That is true digestive efficiency!

Harry the Heron was very proud of his digestive capabilities - and for good reason. I'll be thinking about him as I sit down to Thanksgiving dinner, and wishing I could be so accomplished!



The next time my car gets covered in bird droppings, I won't get angry, I'll just celebrate the digestive miracle that happened in the trees above. Incredibly, birds that eat berries are able to digest their meal in about 30 minutes - down the hatch, fully processed, and onto the hood of my car. How could I get mad at something as amazing as that?

The next time my car gets covered in bird droppings, I won't get angry, I'll just celebrate the digestive miracle that happened in the trees above. Incredibly, birds that eat berries are able to digest their meal in about 30 minutes - down the hatch, fully processed, and onto the hood of my car. How could I get mad at something as amazing as that?


Did you know?

• Most birds can store food in their crop, but a few types of birds - including great blue herons - can keep food in their proventriculus. They can use this food later for their own benefit, or to regurgitate partially digested food for their chicks. If something they regurgitate is too big for the chicks to swallow whole, the parent can re-swallow it and digest it a little more. We learned about this "packaged food" strategy for feeding chicks in a previous issue of Nature Notes. (If you missed that, click HERE to read about How Baby Birds Get Breakfast.)

• Birds don't have bladders. Like all vertebrates (including humans), their kidneys control fluid levels and remove nitrogenous waste from the blood. In birds, this waste takes the form of uric acid, which the kidneys send directly to the cloaca as a thick white liquid to mix with the solid waste. On the other hand, humans produce urea, which is more toxic so needs to be diluted with water. We need a bladder to hold it all. This is another way in which birds are highly efficient. They don't have to drink much water, helping them keep their weight down for flight.

• Humans outperform birds in the sense of taste. Humans have 2,000-8,000 taste buds, while birds only have about 300.



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