Sound From Bird Wings Act As a Predator Alarm

An anonymous reader writes "Biologists have discovered that a species of Australian pigeon has a secret way of alerting fellow birds to predators — a 'whistle' emitted by flapping wings when the bird takes off in alarm. The crested pigeon (Ocyphaps lophotes) is well known for the abrupt metallic-sounding whistle that it makes on takeoff. Many birds have the ability to make vocal cries to alert other members of their flock, but this is the first study to show that flight noise can also serve as an alarm call."

Funny that this has only *just* been researched...

[Mr. Roadkill]

Twenty or twenty-five years ago I noticed that those little buggers made different noises when startled than when taking off normally. I thought that was something that everybody who knew the birds knew about. Guess I should have gone into biology, and taken a little more notice of what was quite literally in my own back yard when I was growing up.

Woodpigeons clap their wings

[Anonymous Coward]

From http://www.gardenbird.co.uk/Wood-Pigeon-Information/Bird-Watching/GBS_birdType_WoodPigeon,default,pg.html

Sometimes they can be seen feeding on nut bags but because of their large size they generally forage on the ground and if they are disturbed when feeding they clap their wings to scare off other birds.

Re:Natural alarm.

[Ninja Pigeon]

Mae here. Actually, we DID do exactly that to control for the possibility that they were simply responding to the louder noise. During playbacks we also played a series of neutral natural sounds (rosella bell calls) that we matched in amplitude to the volume of the alarmed whistle, the birds paid absolutely no attention to them. We also played whistles recorded under non-alarmed conditions at 'alarmed' volume, again the birds did not respond. They only responded to whistles recorded under alarmed conditions, played back at alarmed volume (and once or twice to whistles recorded under alarmed conditions but softened to the volume of non-alarmed whistles). Give us some credit, a lot of time and thought is put into experimental design. In answer to the previous note, indeed the 'alarm' is linked with 'getting out of dodge'. As such, we can not distinguish yet if the whistle is an intentional 'signal' or simply a 'cue', we state this in our paper. Possibly the sound is intended for another purpose (mate choice? species recognition?) and the fact that it also indicates alarm is a side effect. Irregardless of intended function from the perspective of the 'signaller', it still produces a different sound in alarmed flight and co-specific birds are still using it as an indication to flee, and benefiting from doing so. Another note, It is different from the wing noises of other birds in that the upbeat and downbeat produce very different tones resulting in a 'pulsed' sound during flapping. In other birds you just hear an indistinct 'whoosh' during flight, in Crested Pigeons the pulse enables you to hear the faster alarmed flap rate quite clearly. If all birds flew away every time they heard another bird fly (without knowing how alarmed that bird was) they would never get anything done! I expect many species deliver information through noisy take-off's in alarm, its just that the Crested has exaggerated it to communicate the degree of alarm more reliably, thus negating the need for additional vocal alarms. It is actually quite a neat system, it is more inherently honest/stable then standard vocal alarms in that there is a much higher price to 'faking' an alarm, as the bird MUST fly away, and hard, in order to produce an 'alarmed' type whistle. Thus eliminating any benefit it might have received through getting unlimited access to resources. In vocal alarm systems, there are practically no costs to producing false alarms. Additionally, the bird can't 'forget' to produce the sound, the whistle is inherently graded and it also does not take any extra effort to produce. Additionally, since it causes all the other birds to also flee, it offers a benefit to alarm signalling, the escape of the individual who first flies away will be 'hidden' in the flights of others and the huge noise produced by the escaping flock is also likely to double as a way to scare/distract the predator. All at no extra cost, given the bird would be escaping anyway. Anyway, sorry you didn't find it interesting, each to their own. I know i loved working on it, and i think they are fantastic little birds, lots of character :) p.s. Sorry for the super long post. Ooops! Overenthusiasm.

Re:Mourning Doves

[Ninja Pigeon]

Yeah, i think its actually quite widespread. The mourning dove paper didn't manage to get them to flee, but i think that is because i think they amplitude matched alarm and non-alarm volumes. My birds did not flee either when the amplitude of the alarms was not natural, they were still more vigilant though. I think if they redid their work taking into account the volume aspect they would have got the exact same result.

Re:Shame they're so paranoid

[hcpxvi]

In some parts of the continent ( mostly southern Europe: Italy and Malta for sure but France too) it is common for people to shoot small birds for the sheer fun of shooting them. Anything that flies is shot and they don't care if it is edible, or rare, or a protected species. See here [rspb.org.uk] for details.

In the UK, shooting of birds is restricted to (a) Farmers shooting pest species (e.g. crows) and (b) rich people shooting specially-reared game birds (grouse, pheasant etc.) and (c) People with green wellies shooting ducks --- they are usually keen conservationists to ensure that there continue to be ducks to shoot and places to shoot them

This all makes it entirely plausible that typical garden birds in the UK see people as less of a threat than is the case on the continent. Mind you, if that sodding blackbird steals any more of my Victoria Plums I will be very tempted to blow him away.

Re:Shame they're so paranoid

[Canazza]

There are paranoid pigeons in the UK too, there are also some hard bastards too.
In Glasgow, Pigeons in and around Partick station are timid, paranoid and flee at the first sight of people
a 5 minute walk away at the Botanic Gardens I've batted several pigeons out of the air for trying to nick my dinner.

Acts...

[MarkoNo5]

Sound from bird wings acts .... Sounds act, sound acts, mr. samzenpus.

Re:Mourning doves too...

[Ninja Pigeon]

A similar study has actually been done on mourning doves. Crested pigeons also always whistle in flight (both non-alarmed and alarmed), its just that when alarmed the whistle sounds more rapidly pulsed and louder then it does when the bird is not alarmed.

Re:Natural alarm.

[Ninja Pigeon]

This is interesting! There is a lot of evidence that different bird species can recognize the alarm noises/actions of other bird species (with similar predators), and some stuff on monkeys recognizing bird alarms as well. I haven't heard of horses spooking to spooking bird flocks before. I wonder if the horse is spooking to the louder sound of a spooked flock, or if it understands that the birds have seen a threat. I guess it would depend what the birds were most often spooking from, if the birds usually spook to common predators such as snakes, i can see that it could evolve that the horse is utilizing the vigilance of the birds. However, if the most frequent predators were cats, bird of prey etc. the horse would have no need to spook and is more likely responding to being startled by the birds themselves.

Re:Shame they're so paranoid

[CrimsonAvenger]

although it must be said that we're talking about very small birds, no one eats those.

For reference, the Romans occasionally had hummingbirds on the menus at feasts. So people do (or did) eat very small birds.