SONGS DON’T work if you sing out of tune. And if you don’t learn how to sing properly in the first place, out of tune is how you are likely to sing. For humans, that can be embarrassing. For Regent honeyeaters, a species of Australian bird, it may prove far worse than that. Ross Crates and Robert Heinsohn of the Australian National University, in Canberra, who study these endangered avians, reckon that the problems the males of the species now have in learning the songs required to court the females of the species may result in this particular species becoming extinct.
Widespread habitat loss has seen the Regent honeyeater population decline below 400, and those individuals are scattered sparsely across the remaining 300,000km2 of their habitat. Close encounters between the sexes are therefore rare in any case. But the success of those encounters which do occur depends on the male singing to the female’s satisfaction. Since the sparsity of the population also makes it hard for males to learn from their elders how to do this (a problem amplified by the fact that these singing lessons need to happen before a male is a year old) success is by no means assured.
Four years searching the Blue Mountains and Northern Tablelands of south-eastern Australia for male Regent honeyeaters, and recording the songs of 146 of them, have confirmed the two researchers’ fears. As they write in the Proceedings of the Royal Society, they compared these songs with historical recordings of 14 males and found them sorely wanting. Contemporary songs are less complex than those from previous decades. In particular, they are shorter and have fewer syllables. They also vary dramatically from one male to another, with a quarter of males singing songs that are radically different from the standard song. Worse, some males fail to sing any Regent honeyeater songs at all. An eighth of them, predominantly living in areas of particularly low population density, instead sing songs learned from other species, making them unintelligible to their fellow Regent honeyeaters.
One way out of this vicious cycle would be to boost the birds’ population density with a captive-breeding programme, and the Australian government has indeed proposed this course of action. Unfortunately, captive-bred Regent honeyeaters studied by Dr Crates and Dr Heinsohn had unique simplified songs entirely distinct from wild males. If released into the wild they would probably struggle to attract mates.
The answer to this dilemma may be to give captive-bred juveniles singing lessons. The birds could be played Regent honeyeater birdsong when they pecked a key. To provide some semblance of normalcy, the speaker might be hidden inside a model of an adult male. This technique has succeeded with other captive-bred birds. If it does not work here, though, the Regent honeyeater’s future looks grim.■