Twilight is brief in the tropics. The sun drops with none of the lingering obliqueness of its behavior in temperate and polar areas. My visit to Ecuador placed me almost directly on the equator, so after I watched the sunset from a tree canopy, I hustled to get back to the camp. The trail turns completely dark within a few minutes of sunset.

As I jogged along, a song stopped me in my tracks: a pure tone from the rainforest, then another seemingly in answer, then one more from far across the stream. I’d never heard such a sound. The purity of a thrush, the loudness of a goose. Close.

I captured a few seconds (turn up your volume!):

Here are the spectrograms, with time moving horizontally and pitch (frequency) increasing vertically. The whistles are the low dark marks; all the rest of the sounds are insects and distant birds:

These are the calls of tinamous, ground-dwelling birds found only in the New World tropics (first, the variegated tinamou, then the great tinamou, I believe, but neotropical bioacousticians please feel free to correct me). When I studied their biology in zoology classes I never thought I’d be in their presence. Here they were, though, singing within a few meters of me in the Ecuadorian Amazon. Stunning.

Tinamous have strange habits, at least by the standards of other birds. The males defend nests into which multiple females lay astonishingly glassy eggs. The male incubates the eggs, broods the hatchlings, and guards the young. The females wander from male to male laying more eggs. Tinamous seldom fly, and then rather poorly, preferring to strut in the undergrowth of their forested territories.

Recent molecular research strongly suggests that tinamous are the relatives of the extinct New Zealand moas. This grouping is clustered within the larger “family” of ostriches, emus, rheas, kiwis, and cassowaries. So tinamous are a zoological echo of the ancient southern continent of Gondwanaland, a continent now fragmented into many parts, each carrying biological stowaways. The tinamou song is the closest we’ll come to hearing a moa.

In their biogeographic wanderings, the tinamous seem to have picked up the quena from the mountains to the west, slicing through the acoustic tumult of the Amazon with their melodies. Or perhaps the quena, a recent arrival by zoological standards, is inspired by the Andean tinamous?

Tinamous sing at dawn and dusk, so their music rings out only briefly, bracketing  Amazonian nights and days.