Photo by Priyal Khattar
Birds that live in suburban areas exhibit significantly higher levels of territorial aggression than those in the countryside. It is one of the unavoidable side effects of human population expansion on wildlife, a recent study has said.
These birds in urban areas have been found with higher level of territorial aggression that persists throughout a breeding season. "A possible reason for this is that these birds have less space but better resources to defend," said Scott Davies, a post-doctoral associate at the Virginia Tech University in the US.
For the study, Scientists at Virginia Tech and Radford University in the US measured territorial aggression of male song sparrows in 35 urban areas as well as 38 rural areas during the spring of last year. The researchers then played recordings of a male song sparrow and observed how the territory-holding birds responded to the simulated intrusion from a neighbour and found that suburban birds were more territorial.
They approached and remained near the speaker, flapped their wings furiously, engaged in loud singing and then began to produce 'soft song' -- a term that researchers use to describe the quiet, garbled noise that a bird makes, which is predictive of an impending attack. Though rural birds still responded to a song intrusion, they did not respond as vigorously.
"Suburban sprawl is a primary form of human habitat change and though many species can survive in our backyards, their behaviour and physiology may change to cope with shifts in resources and with new disturbances," said Kendra Sewall, Assistant Professor at Virginia Tech University.
The world population is projected to reach 9.6 billion by 2050 and increasing by more than two billion people, according to the United Nations. Though many animals avoid habitats that are impacted by humans, some species can adjust and live in suburban and even urban habitats.
The observation was published in Biology Letters sheds light on the impact of human population expansion on wildlife.