Birds
Turquoise-browed Motmot
Eumomota superciliosa · also called turquoise-browed motmot, torogoz, guardabarranco
The turquoise-browed motmot is a slim, brightly coloured bird of Central American scrub and dry forest, easy to recognise by the two long tail feathers that trail behind it, each ending in a bare shaft with a neat blue-and-black paddle at the tip. When the bird spots a snake, it swings that tail slowly from side to side, like a pendulum — a message to the predator that its cover is blown.
Overview
Turquoise-browed motmots range from southeastern Mexico and the Yucatan south to northwestern Costa Rica, in dry forest edges, scrub, hedgerows, and around sinkholes and ruins. They are about 34 cm long including the tail, rufous and greenish-blue, with a black mask and a brilliant turquoise brow stripe.
The racket tail
The two central tail feathers grow in fully webbed, but a band of weakly attached barbs near the tip wears and preens away, leaving a bare shaft and an intact paddle at the end. A newly moulted bird briefly has a more ordinary tail.
The pendulum signal
When a motmot detects a predator, it swings its racket tail rhythmically back and forth. The best-supported explanation is that this tells the predator it has been seen and an ambush would fail — a “pursuit-deterrent” signal. Tellingly, both sexes do it, and it peaks around predators rather than in courtship.
Nesting
Pairs dig burrows up to about 1.5 m long into earth banks, road cuts, and sinkhole walls, sometimes in loose colonies, and lay their eggs in a chamber at the end.
Status
The turquoise-browed motmot is Least Concern, common, and comfortable in open and disturbed country. It is the national bird of both El Salvador (the torogoz) and Nicaragua (the guardabarranco).
Turquoise-browed Motmot: common questions
Why does the turquoise-browed motmot wag its tail?
The most supported explanation is that it is a signal aimed at predators, not at other motmots. When a motmot notices a potential threat, especially a snake, it begins swinging its long racket-tipped tail rhythmically from side to side. Researchers think this communicates to the predator that it has been detected, and that an ambush is now pointless, so the predator may as well move on rather than waste energy on a hunt that will fail. This kind of message is called a pursuit-deterrent or perception-advertisement signal. Supporting the idea, both sexes wag equally, the behaviour peaks in the presence of predators, and the conspicuous racket at the tail tip makes the movement highly visible.
How does the motmot get its racket-shaped tail?
It is not born with it. The two central tail feathers grow in with a full web of barbs like any feather, but a section of barbs a short way from the tip is only weakly attached. Through ordinary preening and daily wear, those weak barbs fall out, leaving a length of bare shaft with the fully intact end of the feather still attached as a paddle or racket. So the distinctive shape develops over the weeks after the feather grows, and a freshly moulted motmot briefly has more normal-looking tail feathers before the bare zone wears clear.
Where do turquoise-browed motmots nest?
In tunnels that they excavate themselves. A pair digs a burrow, often around a metre or more long, horizontally into a vertical face of earth, such as a stream bank, a road or quarry cut, or the wall of a limestone sinkhole, of which there are many in the Yucatan. The tunnel ends in a nest chamber where the female lays her eggs directly on the soil. Motmots sometimes nest close together in loose groups where good banks are limited, and the same sites may be reused or re-dug in successive years.
What is the difference between the turquoise-browed motmot and other motmots?
The turquoise-browed motmot is one of the more brightly coloured and open-country members of its family. Compared with forest motmots it has a longer, more strongly developed racket tail, a more vivid turquoise brow, and more rufous in the plumage, and it perches more in the open, on fences, wires, and bare branches, where its tail display is easy to see. Other motmots, such as the blue-crowned or rufous motmots, tend to be larger, greener, more retiring, and more tied to closed forest, and some have less pronounced or even un-racketed tails.