[ad_1]
MELBOURNE, Australia — Albatrosses often mate for life, making them the most monogamous creatures on the planet. But climate change may be pushing many birds to “divorce.” a study It says it was released last week by the Royal New Zealand Society.
The study of 15,500 pairs of black-browed albatrosses in New Island in the Falkland Islands used data spanning 15 years. Researchers led by Francesco Ventura of the University of Lisbon found that the divorce rate among birds, which averaged 3.7 percent at the time, increased during the years when the ocean was warmest. It rose to 7.7 percent in 2017.
Albatross divorce is usually very rare. According to the report, the most common trigger for permanent separation is the failure of a chick to successfully wing. In years when the sea was unusually warm, the fact that albatrosses struggled more with both fertility and – the technical term used by the researchers – divorce, heralded an alarming trend for seabird populations in general as temperatures rose globally.
“Rising sea surface temperature has led to an increase in divorces,” Mr Ventura, a conservation biologist, said in an interview.
But the researchers found that this alone did not explain the increase in divorce rates, even after the models accounted for higher reproductive failure in warmer years. “We still see something unexplained,” said Mr. Ventura.
Large seabirds are found in the Southern Hemisphere, in countries such as New Zealand, and off the coast of Argentina. They are known for their extensive travel, wingspan of up to 11 feet, and long lifespans. They can survive for decades. Black-browed albatrosses get their name from their slanted, sooty eyebrows that give them a constant expression of anger.
Albatrosses in partnerships spend most of the year apart, reuniting each season to bring the cubs together. The male usually arrives first on land, where he waits for his mate and heads for their burrow.
“It’s pretty clear that they love each other,” said Graeme Elliott, an albatross specialist with the New Zealand Department of Conservation, who was not involved in the New Island study. “After watching albatrosses for 30, 40 years, you can sort of spot it. They’re doing all these things that we think are important – human feelings, you know – they greet their long lost spouse and they love each other and they’re going to have a baby. This is great.”
Birds usually return to the same mate each breeding season. Couples perform a reunion dance that has become more synchronized over the years. “As the years go by, they improve the quality of the performance – first a little weird and then getting better and better as time goes on,” said Mr. Ventura.
The stresses of warm seas seem to upset this delicate balance, especially if birds arrive late into breeding season or in worse health after flying far in search of food.
“We expect colder waters to be associated with more nutrient-rich and resource-rich conditions, whereas warmer waters are resource-poor conditions,” said Mr Ventura.
The researchers found that some albatrosses in the studied population terminated successful unions and reunited with a different albatross. (Females who are easier to find a new mate for tend to be the instigators of permanent separations.)
“After a challenging breeding season with insufficient resources, more effort and higher reproductive investment may cause stressed females to break bonds with their previous mates and seek a new mate even if they had previously been successful,” the researchers wrote.
New Zealand albatross expert Dr. Elliott said the study’s finding “didn’t quite surprise me.” The researchers said they noticed demographic changes among birds elsewhere as fish populations dwindled.
The number of albatrosses on the remote Antipodes Islands, about 530 miles south of New Zealand, has declined by two-thirds over the past 15 years, according to the New Zealand Conservation Agency.
Climate change is a factor: Dr. Elliott said female birds have deviated quite a bit from their course in search of harder-to-find food, putting them in deadly contact with fishing boats and causing significant population imbalances.
This has left male albatrosses who find themselves single to make desperate decisions, he said. Male-male pairs now make up 2 percent to 5 percent of the bird population on the island. same-sex mating behavior among many species.
Dr. “There are now one and a half to two times as many men on the island as there are women,” Elliott said. “We form these male-male pairs – males can’t find mates and after a while they decide that other males are better than nothing.”
[ad_2]
Source link