The songs of birds certainly sound beautiful to our ears but listen closely and you’ll hear a world of conflict and subterfuge. Take the Preuvian warbling antbird (Hypocnemis peruviana). Males and females live in pairs and they will defend their territories from other duos by singing beautifully coordinated duets.
Theirs is a most melodious partnership but throw another female into the mix and the harmony breaks down. The duet turns into an acoustic battle – the female tries to jam the song of her partner with her own, so that the notes of his amorous solo fail to reach the ears of the intruder. The male in turn adjusts his song to avoid his mate’s interference.
Joseph Tobias and Nathalie Sneddon uncovered this complicated sonic rivalry by recording 27 pairs of wild warbling antbirds in their natural environment in Peru. Males and females sing different tunes and their duets consist of a regular series of couplets – the male always leads and the female chimes in immediately after. These couplets require split-second timing. If she comes in any earlier, the female interferes with the male’s song.
But she often does. The quicker she responds to his song, the greater the interference, and the more likely the male is to take counter-measures. If he’s being sung over, the male abandons his current son and just begins a new one after the female finishes. In very rare situations, she jams him again, and the cycle continues.
To our ears, the buzz of a mosquito is intensely irritating and a sign of itchiness to come, but to theirs, it’s a lover’s serenade. The high-pitched drone of a female is a siren’s song that attracts male mosquitoes. And a new study shows that when the two love-bugs meet, they perform a duet, matching each other’s buzzing frequency with careful precision.
The female Aedes aegypti mosquito (the carrier of both dengue and yellow fever) beats her wings with a fundamental frequency of about 400Hz, producing a pitch just slightly lower than concert A. Males on the other hand, have a fundamental frequency of around 600Hz, about one D above middle C.
Lauren Cator and colleagues from Cornell University discovered the sonic secrets of courting mosquitoes by tethering individuals to pins and moving the females past the males. On two-thirds of these fly-bys, the amorous mosquitoes harmonised. Neither took the lead – instead, both buzzers shifted their flight tones so that the male’s second harmonic (the second multiple of his fundamental frequency) and the female’s third had a mutual frequency of about 1,200 Hz. They synchronised in this way for about 10 seconds.