Early birds feel the heat

The Herald Sun
21 Jun 2006

MIGRATORY birds are arriving earlier in Australia and leaving later, most likely because of global warming, a study has found.

Researchers analysed the movements of migratory birds visiting southeastern Australia since the 1960s. Using published literature, bird observer reports, and observations of bird watchers, the team compared the arrival date for 24 species and the departure for 12 species over the past 40 years.

Heading the study were Macquarie University PhD students Linda Beaumont and Ian McAllan, together with Associate Prof Lesley Hughes. The study is believed to be the largest of its kind in the southern hemisphere, and is published in the international journal Global Change Biology.

The study found half the species analysed -- which included sandpipers, kingfishers, bee eaters and plovers -- showed a significant trend towards earlier arrival since 1960. It showed they were arriving on average 3.5 days earlier each decade across the study group, and staying an average 5.1 days later.

Temperature change in Australia of around 0.5C since the 1960s was "very likely" to be influencing the birds' migratory patterns, Ms Beaumont said. She said the big concern was that the change would alter the life cycles of birds, including when they reproduce. "(A temperature change of) 0.5 degrees for us is nothing, but birds and insects respond very rapidly to changes in temperature," she said. "Birds time their breeding so that when the eggs hatch it coincides with the optimal timing for whatever is the source of their food."

There was also a danger that short distance migratory birds, such as the channel-billed cuckoo, may stop migrating become permanent residents of southeastern Australia, she said.