Just for the birds: The Tanagers | Ornithology


The tanagers are one of the most beautiful groups of birds in the world. When you head to Latin America, various species of tanagers are high on every birder’s wish list. A lot of them are both conspicuous and occur together in multi-species flocks. That creates an extravaganza for birders on the road.

But let’s start here. The western tanager competes strongly for the most beautiful bird in Idaho. Mountain bluebirds, lazuli buntings, black-headed grosbeaks, calliope hummingbirds, and several other species compete as well. But a male western tanager in spring, singing in the morning sun from a nearby tree, is about as good as it gets.

Other tanagers in North America are also lovely. The scarlet tanager of more eastern habitats is striking. The summer and hepatic tanagers of southern states are more understated, but they are red, after all. Red birds are awesome. But our western tanger is definitely the best — red, orange, yellow, and black. All four species are in the genus, Piranga. This is derived from a Tupi (Brazil) word for an unknown small bird. I find this an odd choice as there are countless smaller and more unknown species in South America!

One other thing I love about tanagers is they mostly are not small, not skulky, and not fast moving. Unlike fleeting kinglets or hiding MacGillivray’s warblers, they putz around in the trees and routinely come out in the open. They tend to hang out high in the canopy so look up! The distinctive, burry, robin-like song of our western tanager and their equally distinctive two-note call, tell you immediately where they are. Further, they tend to sing or call over and over. Western tanagers seem eager to be found and seen. Lucky for us!

The tanagers are in the family Thraupidae, in the order Passeriformes. The family has a Neotropical distribution — so they are only found in the New World. For most of my life, the family contained around 380 species. But as species were studied using DNA analysis, it became apparent the group had to be split up. Euphonias and Chlorophonias were taken away and placed with the Fringillidae (various finches). And the genus Piranga, which includes our western tanager, were placed with the cardinals (Cardinalidae).

This demonstrates that looking at birds, or any other species, gives us one idea of ​​how they should be grouped. But using other sources of information — DNA, behavior, vocalizations, or bones — can paint another picture. DNA is ruling these days, and it’s hard to argue against this most granular evidence.

But no matter the taxonomic details, the tanagers — broadly defined — share several similarities. The first is ecology. As I mentioned, they like to stay relatively high in the vegetation, preferring upper branches and treetops. They are less social than many species, although they do occur in mixed-species flocks in the tropics. They are mainly insectivores, although they readily eat fruit when available. Some accounts talk about them fly catching, but I have to admit I’ve not seen that very often.

Although there are some drab species in the tanager group (check out palm tanager), most species are colorful, and those colors include the entire spectrum. Let’s look. With just the western tanger, we already have red, orange, and yellow. But, just for fun, let’s toss in the red-headed tanager of Mexico, orange-throated tanager of Ecuador and Peru, and the yellow-scarfed tanager of Peru.

When I traveled with Barry Walker of Manu Expeditions and some of my birding friends to see the orange-throated tanager on the land of the Aguaruna people in the Peruvian Amazon, we were warned to keep our cameras out of sight and not take any pictures of the people. The Aguaruna men stood around with long, black, wooden spears, and no sense of humor we could detect. We learned they had killed some “missionaries” a few years earlier for their deceptions of the Aguaruna people. I was prepared to follow the rules.

The much-prized orange-throated tanager routinely visited a huge fruiting tree upslope from the village, which was located along the edges of a large river. The tree was known as the “spirit tree” by the locals, although we did not know in any specific detail what that meant. Let your imagination run wild. It is the Amazon. The village chief guided us up a trail to the tree. We were honored to have him with us. Plus, we couldn’t have gotten there without him.

The slight, but unmistakable tension, was broken for me when the chief used his machete to harvest a young pineapple from along the trail. He deftly sliced ​​it into pieces for each of us to eat. It was pineapple nirvana – sweet, juicy, and more flavorful than you can imagine. OK, I thought, we’re definitely going to live for a while longer. My very sticky fingers seemed a minor issue.

We finally arrived at the Spirit Tree. Like many Amazonian trees, it was huge. But it did not go straight up forever, like a Brazil nut tree. Rather, it had enormous branches, like a gigantic oak or sycamore, creating enough arboreal habitat for a whole jungle of species.

I was wringing wet from the heat and humidity. But the worse part of waiting for the tanager to show were swarms of skinny wasps. They didn’t sting (much), but they loved to fly around your head like some gnats you might be familiar with. They also liked to land and just walk around in your hair and on your neck and arms. They were incredibly annoying. It seemed a test of our desire to see this rare bird. On the upside, a whole jungle of species DID visit the Spirit Tree while we waited.

After a few hours, the orange-throated tanager appeared, and we saw it well. We were then eager to leave. It’s safe to say that was by far the most difficult tanager I’ve ever seen. But worth it. I learned a few years later we were the last group to see this species on the Aguaruna land. They stopped allowing visitors.

Returning to tanger colors, dozens of species have some blue on them. Check out the beryl-spangled tanager of the Andes for one nice example (and put beryl in you Wordle quiver). For green, there are many killer choices, including the green-headed tanager of Brazil, competing for the most beautiful bird — period. We can wrap up indigo and violet – and take another splash of green — with the paradise tanager, fortunately widespread in northern South America. Now I know you want to go.

Because most tanagers live in the tropics, and either are residents or perhaps short-distance migrants, one wonders why four species — western, scarlet, hepatic, and summer — busted out and “decided” to become migrants. Why not just sit tight in neotropical forests and skip all the risks of migrating north in spring and back south in fall? Why not behave like so many tropical species who are residents, and who spend year after year learning about the food sources, nest sites, predators, and other costs and benefits of their local patch?

We have to view all of these “decisions” from the perspective of evolution by natural selection. Those individuals who make better choices survive. Those who make poorer choices go away, and only a get a Darwin Award, at best. Over millennia, or less time in some cases, species continue to adapt.

For our four species of tanagers, it’s easy to imagine how individuals with the genes favoring migration were slightly more successful than others. The interesting question is, why didn’t more species of tanagers exhibit this same evolution? Or in a larger view, why didn’t more species of all sorts evolve a migratory strategy? As is usually (always?) the case, it’s impossible to say why something didn’t evolve.

The most common view is that over those millennia some tropical birds gradually moved their breeding grounds to the north. They would have been able to take advantage of vast food resources with less competition and longer days in which to forage. Bird species at higher latitudes have substantially larger clutch sizes (4-6 eggs) than do those in the tropics (2-3 eggs). This advantage alone would be a powerful driver of the evolution of migration, all else being equal.

But some ornithologists think the opposite happened. Birds in temperate climates gradually moved south to escape harsh winters. Of course, both may have happened. And both views simplify extremely complex phenomena. No matter the cause, I’m not alone in being happy western tanagers make the trip to Idaho every year.

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