Life sciences

Divorce rate soars… among birds!

Two-thirds of monogamous birds commit adultery. The drama unfolds while the male is sitting on the eggs, waiting for them to hatch. All of a sudden, the female spots a lively, colourful winged creature chirping a seductive tune. It’s love at first sight. Without casting a backward glance, she abandons the father of her eggs and flies off warbling all the way.

‘Divorce’ among birds is a well-documented phenomenon in life sciences. But what prompts females to love ‘em and leave ‘em? This is what biologist Frédérique Dubois will try to find out over the next few months. Her research team will observe zebra finch couples — those small Australian birds known for their monogamous nature that are nevertheless vulnerable to acts of infidelity. “Specifically, we will be looking at the success of reproduction as a factor in ‘divorce’ rates,” explains Prof. Dubois who came to Quebec from France in 2001 and was hired by the Université de Montréal last year. “For instance, we will take some eggs from a nest and observe the mother’s behaviour. If she leaves her partner because the quantity of eggs is insufficient, then we’ll have part of the answer.”

The ornithologist uses terms associated with amorous human relationships to describe the relationship between feathered males and females. In fact, Prof. Dubois defends her choice of words since they have a scientific foundation. “A change in partner is only considered a divorce when at least one of the two partners reproduces with a new partner while both are still alive and present in the population,” writes Prof. Dubois in her research abstract, referring to Sharmila Choudhury, a pioneer on the subject.

It’s important to realize that monogamy among birds is not an eccentricity of nature. “In ornithology, monogamy is necessary for the provision of bi-parental care. Since both parents are usually needed from the brooding period to hatching, evolution has favoured the mutual support of the couple. In mammals, the presence of two parents is not as vital, which is why monogamy is much rarer,” explains Prof. Dubois.

But sexual selection, in which females are attracted to the best sire available in the population, can really shake things up. By mating with the most colourful, robust and melodious males, the female helps to strengthen the species for future generations. Infidelity therefore has a scientific basis that extends back to Darwinism. While certain birds are less faithful (pink flamingos, grey herons and mallard ducks are the veritable Don Juans among our feathered friends), others, such as the snow goose and the albatros, seem to be faithful to the very end. “Variations correspond to reproductive practices. Species whose nests stay in the same place for several years tend to be more faithful. When birds return to their nesting sites after their yearly migration, they are also reunited with their partners,” says Prof. Dubois.