Urbanisation of crows a “significant moment”
A PAIR OF innovative crows is making headlines after nesting in a building as opposed to the trees in Brisbane – a sign the species is adapting to the urban environment.
One of five species of crow in Australia, Torresian crows (Corvus orru) are found throughout the northern half of the country – and are the only species to have begun nesting on urban structures in populated areas.
The observation comes after Griffith University PhD student Matt Brown began studying the intelligence of the animals, conducting food-reward tests on six pairs on the university’s campus.
Over a two-year period, Matt’s supervisor Professor Darryl Jones says they got to know the pairs well, and one stood out from the others – refusing to engage in the tests, and failing to nest come breeding season.
“We weren’t actually studying that,” Darryl explained. “But it became interesting when one of the pairs didn’t build a nest in a tree, they started taking sticks onto the ledges of the building.”
“They just made a really terrible job of it – I was pretty sure they were a young couple who just had the instinct to carry sticks somewhere.”
Darryl said it became a point of conversation, with colleagues on campus often telling him about the mess the crows had made, until August this year, when the confused pair finally had success.
“Somebody said, ‘hey, they look like they’ve actually made a nest!’” Darryl said.
The pair – named Dan and Danielle – constructed the nest on a small ledge outside the office of bird expert Darryl, successfully rearing two healthy chicks.
“This is a pretty good example of animals living in the city changing their behaviour in a very fundamental way,” Darryl said.
“It’s a big change to build on buildings where people live – it’s a significant moment.”
The crows surprised bird researchers by building a nest on a building, and then copying aggressive magpie behaviour. (Image: Darryl Jones / Griffith University)
Following the finding, a number of experts and birdwatchers have contacted Darryl with similar observations of Torresian crow pairs nesting on urban structures after years of trial and error.
And with large trees throughout Griffith University’s campus, Darryl said there was no need for the change in nest location, instead he sees it as a sign the usually wary animals are adapting to the urban environment.
“Without any doubt at all, this is the beginning of a massive change – the next generation of crows will be building nests on buildings,” Darryl said.
“All those chicks on all these buildings, they’ll think it’s normal to build nests on buildings.”
Urbanisation – the challenges of coexistence
While crows are a familiar sight – and sound – throughout many Australian cities, Darryl said this nesting behaviour has only been noticed by himself and others in the past few years.
And with a nest location within a metre of his office, in an area of high foot traffic, it came with challenges – the pair has started exhibiting the aggressive behaviour of another iconic Aussie bird.
“They would yell at you through the glass, and when they had chicks, they would attack mercilessly – exactly like magpies,” Darryl said.
While women and children did not seem to be bothered by the birds, Darryl and four of his colleagues – all tall men – fell victim to the protective parents’ swooping, thought to be a reaction to a colleague’s efforts earlier in the year to rescue the pair’s prey.
“It was revealed a couple of weeks ago that my colleague Dan saw the crows hassling a water dragon, and he went and rescued the water dragon, so because he was mean to the crows they were mean to him,” Darryl explains.
“They’re very smart birds – they remember people.”