Few birds are as exciting to watch as manakins. They are small, active, and colorful like warblers, have elaborate courtship displays that include dancing and gymnastics, and combine a variety of non-vocal sounds with their singing.
About 50 manakin species inhabit moist forests in Central and South America and feed largely on fruit, which, surprisingly, has allowed them to develop such wild courtship displays.
Because fruit is usually plentiful, manakins are not resource limited, and females do not select males based on their ability to provide food. Consequently, females select males on the basis of individual sexual traits, which has intensified the birds’ brilliant colors, special vocalizations, and elaborate displays.
The non-vocal sounds produced by the males of many manakin species involve wing movements, which can be enhanced by structurally modified inner wing feathers (secondaries). Sounds vary widely and include whirrs, clicks, snaps, and pops. The sounds are produced by combinations of air moving through the feathers, wingtips slicing through the air leaving a vacuum to be filled by rushing air, or wing feathers striking their bodies or scraping fanned tail feathers. The loudest pops occur when the backs of the wings strike each other above the bird.
Freed from visiting male territories across the countryside, sexual selection allows females to simply go to where the males are gathered and observe (read: evaluate) them. Out of this came lekking, a courtship method in which males create individual display areas called leks; they try to attract females into the leks for courtship and breeding. Leks allow females to observe many males in a short time.
Golden-collared Manakin offers an example of a simplified lek system. Males create several leks that are close together. The leks are on bare ground, where the males remove leaves and litter so the females can see them better. Each lek is about 3 or 4 feet in diameter. The leks include several small, slender saplings (half-inch in diameter or smaller) the birds use as perches. The males move rapidly from perch to perch, giving a wing snap while in the air that sounds like a small firecracker.
If a female is within earshot, she may come to the lek and check him out. If sufficiently impressed, she’ll enter the lek and follow his erratic flights. He seems to barely touch a sapling before springing off, with the female in hot pursuit. The rapid and erratic movement continues, then intensifies, reminding me of an old-fashioned pinball machine. When she is sufficiently excited, she perches on a branch and the male joins her, hoping that mating will follow. If not sufficiently stimulated, she will fly off to another lek and see what that male has to offer.
Watch the Golden-collared Manakin’s display
Sometimes, it takes more than one male to properly stimulate a female for copulation. With the Swallow-tailed Manakin, for example, a dominant male (alpha) forms an association with a beta male to help him stimulate the female. The alpha male perches higher above the lek than other males, acting as a sentinel, and sings to attract females.
It might seem illogical for beta and other males to help the alpha male successfully breed, with no reward. The answer lies in the future. If alpha dies or leaves the territory, beta has the best chance to inherit the lek.
If a female enters the lek and perches on a display branch, the alpha and beta males follow and perch next to her, alpha closest. In a jump dance, the alpha male leaps up and hovers in front of the female before circling back to the branch. The beta male leaps off the perch to repeat the dance. Sometimes a third male, from a group of extras near the lek, joins in, which increases the dance line by one and makes the performance more spectacular.
Jump dances continue for a long time (often exceeding 50 jumps) until the female is properly stimulated as demonstrated by her response, such as increased body movements, jumping, and wing flicking. The alpha male signals for the other males to leave, and he does a special solo dance that is intended to lead to copulation.
The most bizarre example of sexual selection is the clear violin-like tones produced mechanically by Club-winged Manakins. Researchers Kimberly Bostwick and Richard Prum discovered the mechanism and first reported it in 2005 in the journal Science.
The inner wing feathers (secondaries) of the Club-winged Manakin include one with a small blade, or pick, on the shaft (rachis) and the adjacent feather with an enlarged rachis, usually with seven ridges. When the manakin shakes its wings over its back, the feathers rub together and the pick scrapes the ridges, creating a tone at 1500 hertz. The tremendous wing speed required to create the sound is provided by enlarged wing muscles. The mechanical production of sound by rubbing structures together is called stridulation; it’s common in insects such as crickets but has not previously been reported for vertebrates.
The dazzling visual and audio courtship displays of manakins reflect strong sexual selection and demonstrate again the amazing behaviors of birds.
This article from Eldon Greij’s column “Amazing Birds” appeared in the May/June 2018 issue of BirdWatching.
Watch the Club-winged Manakin’s dance
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