Yellow-winged Blackbird: Trilling Trile

_{This YouTube video was produced by the American Bird Conservancy.}

The Yellow-winged Blackbird (Agelasticus thilius) is a conspicuous species of the Southern Cone of South America, congregating in colonies in marshes during the breeding season, and forming larger flocks in wetlands, grasslands, and agricultural fields the rest of the year. These birds are also extremely vocal, giving a startling variety of calls, including sharp and percussive sounds, clear and musical whistles, and a range of other rattling, chirping, whining, whirring, and gargling vocalizations. Their song in particular makes use of virtuosic trills, robotic whistles, and mechanical whirring or buzzing sounds, coming across as half bird, half sci-fi robot. This iconic song is also the source of one of the Yellow-winged Blackbird’s nicknames, “trile,” and some authors propose it may also be the origin of the name of the country Chile! As if to make the most of their raucous acoustic capacity, the males of an entire colony will sometimes sing together in one big, cacophonous chorus.

In addition to nesting together in the same space, Yellow-winged Blackbirds also synchronize their nesting in time. Most of the females in a colony will lay within several days of each other. As a result, most of the nests in the colony will be on the same timeline, with eggs and nestlings developing at about the same time across the marsh.

Researchers have found that synchronized nests, as well as nests with more nearby neighbors, are less likely to be parasitized by the Shiny Cowbird (Molothrus bonariensis). This may be due to a “safety in numbers” effect, where more nests at the right stage of development are available to be parasitized, so that each individual nest is less likely to be the unfortunate one chosen by a female cowbird. But there may be a “power in numbers” effect in play as well. Yellow-winged Blackbirds are notoriously aggressive toward nest parasites, and larger flocks of blackbirds all defending their nests at the same time may make their colony particularly inhospitable for cowbirds.

Also known as: Trile (Colloquial, Chile), Alférez (Colloquial, Uruguay), Varillero ala amarilla (Spanish)

Learn more at: https://abcbirds.org/birds/yellow-winged-blackbird/