The “murmuration” of starlings swirling about Hobart’s skies vanished with the arrival of spring.
The starlings flock in their hundreds, sometimes thousands, during the winter months as they travel to and from communal roosting sites.
The biggest roost in the Hobart area is on the concrete slabs and girders supporting the Tasman Bridge. There, clouds of starlings can be seen in the early morning or late afternoon, flying in tight formation to avoid the attention of the peregrine falcons which also patrol the bridge in the winter months looking for an easy meal.
I always visit the bridge in winter to see the peregrines – the fastest creatures on earth which can reach speeds of more than 300 km/h in their swoop, or stoop – chasing starlings, trying to pluck slow moving individuals from the air.
This winter, however, I paid more attention to the starlings than I usually do.
One afternoon there appeared a particularly large flock, twisting and turning like a cloud of mist, as a peregrine moved among them. The dance is called a murmuration in reference to the sound of all those wings beating in unison – a murmur.
Scientists in Britain have started to unlock the mystery of this cohesion, using high-speed photography to plot the movements of individual birds within the vast flocks. This has revealed each bird constantly observes seven birds around it to judge direction. The number seven is thought to be vital, based in part on nature’s seven possible directions: left, right, up, down, forward, back and centre.
This theory still holds sway although some other recent modelling of starling flight suggests it is the opacity of the flock that also matters – the amount of sky each bird can see
If you are a starling, when one of the seven birds within your little group changes direction, so do you. Your movement is telegraphed instantly to others flying close to you. They react and within a split second the message reverberates through the entire flock.
There is no regular leader, which might sound surprising. Within the flock just one or two birds – different on each occasion – might suddenly change course when a peregrine appears. The seven around them follow, sparking the chain reaction.
The starling might be an amazing bird but it receives a bad press in Tasmania, because of the damage this introduced species does to crops. It is a cavity nester and so also takes the homes of native birds that require nesting hollows to breed. These comprise all the parrots.
Looking for breeding sites, the starlings leave their Tasman Bridge roosts in spring to head to the suburbs and country. When I see the murmurations in winter, often set against the amber sky of a setting sun, I am filled with sadness, knowing what stress awaits our parrot populations.