Monogamy is not particularly widespread among birds, there are many species that indulge in extramarital affairs or have more than one partner. When a bird is monogamous, however, it takes it very seriously: swans, geese and albatrosses, to name a few, are famous for their lifelong bonds, and more generally all seabirds are seen as examples of unshakable monogamy.
Now, however, we have discovered an exception: female Nazca boobies have an eventful sexual and romantic life, and the final choice of partner falls solely on them – the males can only watch, and hope. A study published in PLOS One.
Male shopping. Present throughout the eastern Pacific, the Nazca gannet is especially widespread in the Galápagos, where the Wake Forest University team conducted the study. Which lasted 74 consecutive days of constant observations of the behavior of the females of this bird during the mating period. It’s not hard to summarize what they found: Females move from one male to another until they find the one they really like. We’re talking about important numbers: the record belongs to a gannet who changed 16 partners over 74 days.
Physically inferior. Interestingly, the males do nothing to react to this behavior: they do not attack each other to conquer the females, nor do they attack the females themselves. The reason is easily explained: male Nazca gannets are smaller and frailer than females, of whom they are also somewhat afraid. This is why they are free to do what they want, and to choose their partner as and when they want.
The “right” one. Another important detail concerns “the right male”. Until they have chosen their reproductive partner, female Nazca boobies do not begin to ovulate: this means that encounters with males are “just sex”, and have no reproductive purpose. Once one of these males satisfies the female, things change: the latter reduces (or eliminates) her extramarital relationships, and above all makes herself available for reproduction.
Just sex or true love? The fact that most of the Nazca gannet’s sexual encounters do not lead to the fertilization of an egg may seem strange: why waste energy and not go straight to actual reproduction?
The authors of the study do not yet have an answer to the question, but we can perhaps assume that these birds are very cautious: before investing time and energy in a male, they want to make sure that he is really the right one. Or, who knows, free sex is just a lot of fun!
