The Hairy Trees of Mexico

January 1, 1997 by Russ Greenberg

We're starting our bird banding operation today. Like I said before, this means we'll be out in the field from dawn to dusk until I leave to go home on Friday.

Yesterday, we took a trip high into the mountains to find a strange kind of insect that we discovered in another part of Mexico a few years ago. This insect is stranger than fiction and had only been reported from the oak forests high on the slopes of mountains in the very southern state of Mexico known as Chiapas.

These oak woods were on the lands of the Totzil Mayan Indians of a community known as Zinacantan. You can tell where the Mayan people you see come from by the designs and colors of their traditional dress and the people of Zinicantan (where the strange insect lives) have clothing with lots of pink. One day when I had finished studying the strange insect in the hills behind the village of Zinicantan, I passed by a ceremony where all of the men of the village were standing solemnly while a cannon shot fireworks into the sky.

The insect is weird. At first we had no idea that was even an insect or what it was. It lives most of its entire life hidden under the bark of the tree where it sucks sap. Because it never moves or visits other bugs, it has no visible legs and no antennae—it's just a sack with a mouth. It does grow a long white hair out of its rear end—a hair of wax. If this hair is not broken off, it can come out of the bark of the tree 5 - 7 inches! So when the insect is around all you see is a hairy tree. But that is not the strangest part. Out of the end of these hairs comes little drops of very sweet nectar.

And this nectar is why I study them. The nectar is fed on and fought over by birds. The toughest bird tries to chase all the other birds away so that it alone can glean the glistening droplets. Almost all the birds that feed on the honeydew are migrants from the North, and of the migrant swarm that hang around the affected trees, the Audubon's Warbler is the king. When this small insectivorous bird from the mountains of western North America has had its fill, adult male Townsend's Warblers take over the top-dog slot. Female and young male Townsend's Warblers, Wilson's Warblers and other migrants sneak into the honeydew patch while the dominants aren't looking. On top of the warbler wars, hummingbirds dart about and sapsuckers lap up droplets from the trunk. What's particlarly interesting is that the birds at every clump of infected trees are pretty much the same.

At any rate, we wanted to know if this strange insect is found in other parts of Mexico (like the mountains of Veracruz where we are). Now the insects are a little difficult to find - you would think a hairy tree would be obvious - but the hairs are thin and white (like some of mine) and sometimes not so easy to see. But what happens is that a fungus covers the bark where the insect is and the fungus also lives on the drops that spill from the white hairs. The fungus is black and so the magic trees are black from a distance and it makes the woods look a little spooky. Also, you can hear the fighting voices of the birds.

So looking and listening we went to the highest woods we could find above the small village of Naolinka. Most of the area was farmland, but we spotted some forest on a distant ridge and drove and then climbed into the woods. When we got there it was windy and we couldn't hear anything. But later it calmed down and we heard the heavy chip of the Audubon's Warbler and saw the spooky black bark and then the hairy trees with nectar dripping. It got so calm we could smell the sweet honey in the air.

So now we know that the funny insect and its fungus and bird lives all over Mexico. We also saw the mystical Aztec Thrush. But that's another story.

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