A melancholic liquid song floated through the understory. Reinaldo and I had left the lodge at Mt. Totumas early that morning to see if we could catch the dawn chorus. The night insects had not yet completely shut down while the birds had begun to wake up when we heard this tune. After a short pause, a clear whistle drifted through next. Reinaldo whispered Ruddy-capped Nightingale-Thrush. This montane forest was thick second-growth and ideal habitat for this member of the genus Catharus.
This genus has twelve living species. Two, the Swainson’s Thrush and Hermit Thrush, breed in Western Washington, where I currently live. Those, too, have beautiful songs. However, this nightingale-thrush has a rich set of phrases that carry far. Sometimes they will sing more than 100 of them before taking a break. This one was putting on a good performance; fluty trills, whistles, warbles, and slurs kept filling my ears with delight.
Two other Catharus species breed at Mount Totumas, and the Swainson’s Thrush migrates through on its way back north from its wintering grounds in the Andes. The Orange-billed Nightingale-Thrush breeds at lower elevations and the Black-billed at higher. The Ruddy-capped fills this in-between range on these mountains. Reinaldo took me up into La Amistad International Park to find the Black-billed, and we hiked down to the flood plain of the Rio Colorado to see the Orange-billed.
The diverse phrases of the Ruddy-capped continued to float around us. It sounded like a woodwind quartet, right here. Songbirds create their song in the syrinx, which lies at the base of the trachea and top of the two bronchi. With an elaborate set of muscles, they can control the tension of the wall of each bronchus. As the air passes over this tissue, it oscillates, creating each note. Remarkably, a bird, like this thrush, can control the syrinx at the top of each bronchus separately, allowing them to make different notes in each. Perhaps, this individual is alternating sides or even using both simultaneously to harmonize with himself.
I could listen to this melody all day.