Females prefer bigger bones


The male club-winged manakin (Machaeropterus deliciousus), native to the Equadorian/Colombian Andes, uses wing-produced sonations to attract a mate. The secondary wing feathers of the males are grossly enlarged and are resonated by the birds (at around 36 knocks in 0.33 seconds) to produce a harmonic ‘ting’ sound.

Fancy plumage, courtship behaviours and song in male birds are often the result of sexual selection by female choice. All of which are associated with a cost to males (whether energetic or a risk of predation) and provide females with an opportunity to assess male quality before deciding who contributes to their offspring.

Interestingly, the ulnae (wing-bones to which the secondary feathers are attached) are completely solidified in these males, with volumes three times greater than those in other birds of a similar size. Altogether, this results in a massive bone, which should assist with the sound production.

The ulnae of three similar sized birds, closely related to the golden-collared manakin (left), and the golden collared-manakin (right)


A solidified (not hollow) wing bone has never before been reported in a volant bird, and is perhaps, in this case, a consequence of female choosiness for song quality.

A cost to these males may be the loss of the benefits of hollow wing bones associated with improved flight efficiency in birds, representing a trade-off between mating success and fight efficiency.


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