Squawks, cheeps, chirps and twitters: what does it all mean?

Volume 10 Number 9 September 8 - October 13 2014

Photo: Wikipedia Commons
Photo: Wikipedia Commons

 

Andi Horvath asks the experts to translate the sweet sounds and raucous cacophony of birds. 

As the day draws to a close around dusk, there are certain clusters of trees at particular locations around the suburbs that seem to attract large numbers of birds. 

You can’t often see the birds in the trees but you can certainly hear the cacophony of bird chatter. It has the excitement of a schoolyard, the intensity of a sports match with tones of parliamentary question time. 

A quick office poll knew of these loud dusk gatherings on Hoddle Street near the entrance to the M3 and a supermarket car park in Heidelberg. So what species of birds attend rowdy town hall meetings? Why those trees? Why twilight? What is the yelling match about? 

Dr Michelle Hall currently works with Associate Professor Raoul Mulder, from the University of Melbourne’s Department of Zoology on the behaviours of fairy-wrens. A recent paper reported that male fairy-wrens can use song to signal their size – bigger males sing some song types at a lower pitch.

“The dusk gathering cacophony is a phenomenon called communal roosting, and is relatively common among bird species that live in flocks,” Dr Hall says. 

“Birds like starlings, sparrows, various species of crows and parrots can also roost communally at night. 

“Possible functions of roosting communally are reducing heat loss (thermoregulation) and safety from predators. In other words, there is safety in numbers, from predators like owls.” 

Diurnal birds (those active during the day and inactive at night) can’t see very well at night, so they need to settle into their roosting spot before darkness falls.

“In some cases, the noise may be related to a bit of jostling and conflict over the best locations in the tree. Another possible function of communal roosting is information transfer. Examples could include information about nearby foraging opportunities or simply social information like finding out who is around.”

Dr Karen Rowe, bird researcher and post-doctoral fellow at Museum Victoria says the birds roosting at the Heidelberg supermarket car park appear to be introduced Indian Mynas. 

“What is interesting is when you look up into the tree it’s quite difficult to see them, making this perhaps an excellent choice of tree for them.”

Dr Rowe says bird chatter is so diverse because “different species have evolved nuances in their conversations, but in general the bird noises are warnings like ‘Hey everyone, threat approaching’, or courting signals like ‘Hey ladies check me out’. “They are also social like ‘Where is my group’, and in the case of territorial birds like the Noisy Miners ‘This is my turf’.

“The Noisy Miners are aptly named. These honeyeaters are very vocal, gregarious birds. They also display aggressive male-to-male and female-to-female conflicts. Chicks will also demand unrelated adults nearby feed them. That’s a lot of chatter.”

While some species like the Noisy Miner adapt to urban habitats, many species have become extinct or are endangered by habitat destruction.

Dr Rowe works on monitoring species numbers; not with binoculars but by developing a system that places recorders in specific locations and software that recognises birdcalls. 

Like the phone app Shazam that identifies ‘What song is that?’. That way we can keep an eye and ear on numbers of these essential members of our ecosystem.