RESEARCH: Albatrosses divorce more often when ocean waters are warm

Research scientists think that albatrosses divorce and seek new partners when conditions are harsher than usual, reported Science News in November 2021. The research was documented in the Proceedings of the Royal Society, Series B.

The albatross is a large seabird in the Diomedeidae family. The albatross is a monogamous bird, which means that it stays with the same partner for life. However, when ocean waters are warmer than average, more of the albatross birds break up and look for a new partner, says a recent study.

Researchers at the University of Lisbon in Portugal studied albatrosses on New Island in the Falkland Islands. They collected data from 2004 to 2019 on a large colony of the Black-Brown Albatross (Thalassarche melanophris). They recorded nearly 2,900 breeding attempts in 424 females. They tracked bird break ups and they also measured weather conditions, including the temperature of the ocean waters.

The researchers found that the main reason for a divorce in the albatross colony was breeding failure. Each female lays one egg. If the egg did not hatch, it was recorded as a breeding failure. Females who had a breeding failure were over five times more likely to separate from their partner than females who had a breeding success – whose eggs had hatched. 

In some years, the divorce rate was lower than 1%. This rate increased to 7.7% divorce rate in 2017 when the ocean waters recorded the warmest temperature during the study period 2004-2019.

When the ocean water was the average temperate, about 4% of the birds in the colony break up with their partner (divorced). However, when the ocean water was warmer than average, about 8% of the birds in the colony split up. 

There is a benefit when albatross pairs stay together. Researchers say that pairs that stay together have good familiarity and good coordination, which helps when they raise their young. Francesco Ventura, a conservation biologist at the University of Lisbon, says that stability is important in marine environments. 

Researchers also found that females in successful breeding pairs were more likely to be affected by the harsher environment than males, unsuccessful females, and females that didn’t breed (didn’t lay an egg). When the ocean temperatures cooled in 2018 and 2019, the divorce rate cooled (decreased). 

The scientists think that warmer water means that there are fewer nutrients in the sea. Some birds might stay longer over the ocean looking for food, and therefore spend less time on land in the colony. If the pairs of albatrosses return to the colony at different times, this can lead to divorce. 

Scientists think that stress might affect the divorce rate too. But a bird might incorrectly think that its partner is stressed, rather than knowing it is related to the harsher environmental conditions. So, they separate, even if they had a breeding success. This may mean that they are divorcing for the wrong reason. 

If the albatrosses divorce for the wrong reason, this could lead to lower breeding successes, which means that the population declines. Francesco Ventura says, ‘If you imagine a population with a very low number of breeding pairs … this might have much more serious repercussions.’

Photographer: Martina Nicolls


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