Laura Erickson's For the Birds

Wednesday, July 15, 2020

Peppered with Flavor

Blue Jay eating cherries from Russ's tree.
Many fruit-eating birds are attracted to red-colored fruits, whether they're sweet or hot. 

Back in 2018, researchers at Iowa State University published a paper about how birds in the Mariana Islands have a mutualistic relationship with a capsaicin pepper plant that grows wild in the forests of the Mariana Islands. Capsaicin peppers are native only to the Americas, but have been cultivated in Micronesia for 300-400 years, brought there by early explorers. Interestingly, Guam is the only island in the Mariana Islands group where this pepper is rare. It’s also the only island in the group that has lost virtually all its birds thanks to the introduction of the brown tree snake.   

Capsaicin peppers are unpalatable to mammals, being so hot, but many birds deal with the taste just fine. Many scientists explain that birds can’t taste peppers, but hummingbirds certainly can. For a while, people were recommending adding peppers to sugar water to repel bats from hummingbird feeders, but the pepper repelled hummingbirds just as completely—they obviously can taste it, and obviously do not like it. 

Ruby-throated Hummingbird sticking out her tongue.

The issue is more likely that many birds can taste hot peppers, but that the taste doesn't bother and may actually appeal to many of them. Capsaicin peppers are very nutritious, and it’s quite possible that their hot taste evolved specifically to repel mammals while attracting at least some birds, because birds do a much better job than mammals of spreading pepper seeds. 

Mammals chew their food, which destroys most fragile pepper seeds. The powerful gizzard of some seed-eating birds can pulverize pepper seeds, too, but fruit-eating birds don’t have that kind of muscular stomach. Their beaks may break a few seeds as they devour a pepper, but most of the seeds are swallowed whole, run through the bird’s digestive system, and germinate wherever the birds poop them out.  

Passing through a bird’s gut obviously removes the pulp—the nutritious element the birds are eating the peppers for. The Iowa State researchers found that when the pulp is removed in other ways, the seeds don’t germinate as well as when they go through a bird's digestive system. One bird the researchers focused on in lab studies was the Micronesian Starling—seeds germinated easily after these starlings "processed" the peppers. Intriguingly, the local name for the pepper plant thriving throughout most of the islands studied is "donne’ sali chili." “Sali” is the local name for the Micronesian Starling.   

Even though I hadn’t read about this research until just this week, KUMD’s Lisa Johnson alerted me to it when she was listening to a segment of The Splendid Table. Francis Lam interviewed botanist Heather Arndt Anderson, and noted that many sweet and aromatic fruits are propagated by animals; he wondered how chilis could have an evolutionary advantage by hurting animals that could potentially help propagate their seeds. She said:  

The thing with birds is that they don't have capsaicin receptors in their mouths, so they can't actually taste the spiciness. That's why birds have played such an important role in spreading chilies, whereas mammals have tended to avoid them – non-human animals I should say.  
That is the way not just botanists but many ornithologists see the issue. But really, all we know for certain is that most birds aren’t actively repelled by the taste, and that hummingbirds certainly can taste peppers. The red color of ripe chili peppers definitely attracts birds (including hummingbirds), but birds also notice and are selective about the flavors of most food items. 

The truth is, we really don't understand much about the avian sense of taste. Scientists used to say ducks had no taste receptors whatsoever because they found none on their tongues. But it turns out duck taste buds are concentrated on the tip of their bill, a useful adaptation for turning away from something unhealthful before it can get into the mouth. Birds eating capsaicin peppers may enjoy the hot flavor as much as some humans do, or the flavor may be somewhat blunted but still appealing to them. At this point, we just don't know, and the birds aren’t talking.  

Black-throated Gray Warbler
Photo by Patricia Ware via Wikipedia

The hottest pepper I personally ever ate is forever associated in my mind with a bird, but involves the mammalian, not avian, sense of taste. I was on a birding trip in south Texas and we’d stopped at a McDonalds to buy bag lunches en route to a birdy picnic site. That McDonalds had a big jar of jalapeño peppers on the condiments table, and you could put what you wanted into a French fry bag. It seemed like such a novelty, and I love jalapeño peppers, so of course I took a few. I got settled in at a picnic table, and just as I was about to take a tiny taste of one, someone yelled out “Black-throated Gray Warbler!”   

I’d already learned that you have to be careful about everything you eat in Texas, because so much Texas cuisine is way spicier than Midwestern fare. But a Black-throated Gray Warbler! I grabbed my binoculars and took off, unthinkingly popping the entire pepper into my mouth.  

After three or four steps I stopped dead in my tracks, my eyes spurting tears onto the inside of my eyeglass lenses. I’d never tasted anything nearly this hot before in my life, and I couldn’t even wash it away since I’d left my drink on the picnic table. My mouth and throat were in pain and my eyes kept gushing, but being a birder at a certain level of fanaticism, it never occurred to me to head back to the picnic table and at least get a drink. 

I saw the warbler through badly blurred eyes. It wasn't even a lifer, but I did add it to my Texas state list. And ever since, the memory of that incident comes to mind any time I see a Black-throated Gray Warbler with its distinctive eye marking, appropriately spicy yellow and shaped just like a tiny jalapeño pepper. 

Photo courtesy of Erik Bruhnke. Copyright 2020, all rights reserved.