Taste In Birds

Summary: How come birds always spit out that nasty tasting caterpillar? Do they have a sense of taste?  Join Cheryl and Kiersten as they answer this question!

 

For our hearing impaired listeners, a transcript of this podcast follows the show notes on Podbean.

 

Show Notes:

“Chapter 13: Taste in Birds,” by Shira L. Chelend Shoval, Zehava Uni, and Colin G. Scanes, Sturkie’s Avian Physiology (7th Edition) 2022, pg205-222.

Our email address, please reach out with comments, questions, or suggestions:  thefeathereddesert@gmail.com

 

Transcript

 

Taste in Birds

Kiersten: Intro: Hello Feathered Desert listeners. Today Cheryl and I are here to talk about the sense of taste in birds. Now, if you’re anything like me, you grew up thinking birds had no sense of taste, but how come they always spit out that nasty tasting caterpillar? Well, we’re wrong! Birds, including songbirds, DO have a sense of taste and that’s what we’re going to talk about today.

 

Cheryl: If birds have a sense of taste, they have to have taste buds. And they do! Compared to mammals they have far fewer taste buds but they do have them.

Humans have taste buds on their tongue, and if you remember from grade school science, each type of taste has a different spot on the tongue. A spot for sweet, and spot for sour, and so on. Birds’ taste buds are found throughout their mouth not on their tongue. The greatest concentration of avian taste buds is found in the skin around the salivary glands of the mouth and the back of the tongue, and in the back of the mouth at the beginning of the throat.

How many taste buds do birds have? That answer depends on the species so, let’s look at the numbers.

            One day old domestic chicken – 5 to 12 taste buds

            Adult chicken – 24 taste buds

            Blue tit – 24 taste buds

            Bullfinch – 41 taste buds

            Pigeon – 59 taste buds

            European Starling – 200 taste buds

            Parrot – 300 to 400 taste buds

Let’s compare these numbers to some other animals to give us some perspective.

            Adult domestic cat – 2755 taste buds

            Human – 6974 taste buds

                        Rabbit – 17,000 taste buds

                        Ox – 35,000 taste buds

                        Catfish – 100,000 taste buds

 

Kiersten: The study of taste in birds didn’t get off the ground until the 1970’s. It began with research into ducks. We found that ducks have 400 taste buds and if they used the tips of their beaks to pick up a pea, they could tell the difference between a normal pea and one that was unpleasant tasting. Research continued from there and one of the questions that scientists ask now is what different flavor profiles can birds recognize.

            There are five recognized flavor profiles that humans can taste sweet, salty, sour, bitter, and umami. Scientists studied these five flavor profiles to see if birds could detect them in their food. Let’s start with the sweet profile.

            Frugivores, birds that eat mainly fruit, and omnivores, birds that eat fruit, meat, and seeds, appear to prefer sweet more than other birds that are mainly seed foragers. They can actually tell the difference between different types of sugars. For instance, sucrose versus glucose versus fructose versus xylose. In scientific experiments, the birds tested, such as European starlings, Cape sugarbirds, and Lesser double-collard sunbirds, preferred certain types of sugars over other types. Overall, it appears that the main preference was for sucrose. The sunbirds and the sugarbirds didn’t even bother absorbing the xylose when offered that, it was simply excreted.

            Preference was based on concentration levels when mixed with filtered water. Each species had different preferences based on which solution offered them the best caloric intake in regards to their specific lifestyle needs. And, yes, they tested hummingbirds! As we know they are one of the most famous nectar drinking birds in the world and they are picky about what they choose. It has to be just right for them to revisit a feeder and they can tell when the mixture is off by only 1%. So, remember 1 cup of granulated sugar to 4 cups of water. It’s the magic solution.

 

Cheryl: After sweet, one of humans’ favorite taste profiles is salty. This is actually the only real craving our body ever physically tells us about since sodium is extremely important to proper nerve function. Sorry, but your craving for chocolate is not a true physical craving.

            When it comes to birds, the salty taste acts more as a deterrent than something that they favor. It’s important for birds to monitor how much salt is in their diet because too much can be dangerous and even deadly. In experiments, parrots rejected solutions with 0.35% salt levels or above and pine siskins rejected solutions of 37.5% or higher. The difference here is probably based on their dietary lifestyle. Parrots eat a lot of fruits while pine siskins eat mostly seeds and insects. Pine siskins can tolerate more salt in their diet. Red winged blackbirds and European starlings actually preferred water with a tiny bit of salt. They chose a sodium solution with 0.1% to 1% salt over clear, distilled water.

            Pigeons are even more sensitive to salt solutions and they very quickly learn to tell the difference. Pigeons were presented a solution with a tiny amount of salt that was safe for them to drink and a solution with a toxic level of sodium. In under five minutes, they determined which one was okay to drink. That’s a pretty smart bird! This also proves that the pigeon was basing its decision on taste not side effects from drinking the toxic solution.

            Sour is the next taste profile. Sour taste is typically associated with fermentation and, in birds, usually results in rejection of the food. The sourness detection level in various bird species is different which is, once again, most likely related to their natural diet. The red-winged blackbird and female starlings actually preferred their water with a tiny bit of citric acid even though most birds reject sour foods.

 

Kiersten: Let’s move on to bitter. I think this is the taste that started everything because, like I said in the opening, why do birds spit out bitter tasting caterpillars if they can’t taste? For that matter, why does the caterpillar bother making itself taste bad to ward off one of its most numerous predators if that predator can’t taste the bitterness.

            To test the bitter palate scientists used quinine in a solution. It’s harmless to the birds but has a bitter taste. The threshold for bitter in birds was way lower than the sweet and salt. Birds do not want to eat anything bitter. This is most likely because bitter food often means poisonous food. Even European starlings, who preferred slightly salty and slightly sour solutions, completely rejected anything with even a tiny level of bitter. 14-day old domestic chickens could tell the difference between untreated food and food treated with 0.2% quinine solution. This shows how important avoiding bitter food is to bird survival.

 

Cheryl: Umami is the last flavor profile and we only have a little information about the ability for birds to detect umami. It was only accepted by scientists as an actual flavor profile in 2008, so research involving umami is lacking in more than just birds. What we do know is that male starlings prefer solutions with 0.7% to 1% umami over clear, distilled water. We also know that the umami receptor gene has been found in chickens’ genetic code.

 

Kiersten: Conclusion: In closing, birds do have a well-developed sense of taste that corresponds to their feeding behavior. So even though birds have fewer taste buds than other animals they definitely have a well-balanced sense of taste that helps them pick just the right food to flourish.