In approximately 279 BCE, the Roman empire, after invading vast swathes of Europe and the Mediterranean, set its sights on the island of Corsica off the French coast. Legions landed on the sandy beaches and the air swelled with the horns of battle and the beating of sandalled feet against the rocky ground. Again and again the legions threw themselves at the oak shrubland in an attempt to tame it and the inhabitants of the island. Again and again, the legions were pushed back. The reason? The interior of the island is covered with the Maquis, a labyrinthine shrubland so dense that only wild boar and people who know the way can make their way through. The swords and military power were no match for the strength of the oaks and the Romans had to resign themselves to marching around the edges of the island. This empire that brought kingdoms to heel, that made innovations, and launched navies, was humbled by a shrub. The romans settled for installing a governor and mostly leaving Corsica to handle its own affairs.
It’s presumably for the same reason that the Roman empire never conquered the Grand Mesa in Colorado. The sides of the mesa are covered in Gambel oak thickets so dense that it takes hours to go a single mile. Most people who visit keep to the singletrack trails on top of the mesa (including the ultramarathoners, but that’s a story for another day). Only the foolhardy venture into the oaken labyrinth. The foolhardy, and the birders.
Many new world warblers absolutely love the dense shrublands—it’s one of several notable differences between warblers and roman legionaries. They perch directly overhead or within arm’s reach, close enough that you don’t need binoculars to make out their markings. For the ones that aren’t trying to glean insects directly out of your hair, their song is the best way to identify them. Most warblers have a high-pitched, two-parted song.
Yellow warblers have variable song patterns, but they sing in very pure notes. They know it too—you can recognize them with the mnemonic sweet-sweet-I’m-so-fucking-sweet.
The clue to distinguishing the others is in their names. Virginia’s warbler has a slower cadence than a yellow warbler, as though it has a southern drawl.
The MacGillivray’s warbler’s song has a ringing quality. Imagine a warbler that sings with a Scottish burr.
The song of an orange-crowned warbler drops in pitch, much like the head of a French monarch drops into a basket placed strategically placed under a guillotine.
I, however, am not a new world warbler, and did not enjoy navigating the three-dimensional maze of shrubs. My transect was a green hell. I followed game trails until they petered out, and sometimes crawled to get through the branches like a wild boar in the heart of Corsica. The branches tore my skin and my trousers alike without reproach. At one of the points, I realized I lost my timer, but there was no way I was willing to retrace my steps to find it.
At one point I reached the rim of a gully and looked out over the sea of branches I had to traverse to reach my next point. To make it even more difficult, the gully was littered with dead trees and even if I made it through the living shrubs I still had to crawl under, over, or across the fallen wood. Some of the trees had fallen on top of the shrubs, however, and if I held out my arms for balance and walked over them, I could cross the gully by stepping from tree trunk to tree trunk with only minor forays into the tangle underneath. It was a brilliant plan, until I looked down and saw that the log I was currently balancing on was 6 feet above the ground. If I fell off it, I would fall into the morass of shrubbery below with no way of righting myself, stuck like a turtle on its back. The shrubs would swallow me whole, my bones lost and mingling with the branches until next year’s field tech stumbled across them.
It was a relief when, after five and a half hours, I dragged my ragged and bloodied carcass out of the oaks and back onto the trail back towards my car. The sides of Grand Mesa were better left to the warblers.
You were lucky there are no wild boar in the Grand Mesa. Since for many their eyesight has been ruined by headlights of cars, they are extremely suspicious and bad-tempered.