Got cheated on recently? These birds probably did, too
A look at some of nature's most promiscuous birds
What’s your body count? I’ve had friends say 3, I’ve had friends say 10, I’ve even had one friend say 36! But that’s honestly nothing compared to some of these sexy, salacious birds.
Saltmarsh Sparrow: 95% of females mated with more than one male during each nesting period!
The Saltmarsh Sparrow, a bird that lives in the marshes of United States of America, is now recognised as the world’s most promiscuous birds, with extreme levels of multiple mating. (A marsh is a wetland habitat at the edge of waterbodies like lakes, and unfortunately for the animals that live there, marshes are very prone to flooding.)
In 2010, researchers found that 95% of females mated with more than one male during each nesting period. One in three nests had a different father for every chick, and the chance that any two chicks in the same nest have the same father is only 23%!
Of course, we’re not here to slut-shame: it turns out this unusual behaviour could be a survival mechanism due to coastal flooding. Because these sparrows nest amongst the saltmarshes (hence their name) they are vulnerable to frequent high tides, which can cause a high level of nest loss.
Saltmarsh Sparrows build their nests on the low-lying grasses around the marsh. It’s a race against time for a family to raise their chicks - it takes about four weeks for baby sparrows to fledge. But very high tides occur also roughly every four weeks.
If a Saltmarsh Sparrow is slow to copulate, they risk losing their baby chicks to rising tides. Once they’ve lost their young to flooding, they must re-nest almost immediately in order to beat the four-week countdown and help the new set of young survive.
This means that female birds do not have time to look for and invest in the ‘best’ male partner. There’s no elaborate mating rituals or gift-giving. Instead, it seems that females mate with several males - whoever comes first.
Superb Fairywren: socially monogamous, but sexually promiscuous
These are actually some of my favourite birds, and I hope their story on sexual promiscuity will endear them to you!
Superb Fairywrens are tiny little birds that can be found in Australia (I spotted my first ones in Sydney!) and they are socially monogamous birds that bond for life. However, they are sexually promiscuous, and both males and females will regularly mate with other individuals. A deep dive into the nests of Superb Fairwrens reveals that a proportion of young will have been fathered by males from outside the relationship.
This is because the Superb Fairywren is a ‘cooperative’ breeding species. Instead of having just one pair of parents raise chicks and defend territories, the birds will team up with younger birds, mostly males, to get the work done. Often, these younger males also had the chance to mate with the main female Fairywren!
Why do they do this?
One theory is that their habitats are not particularly rich, and the parent-birds need all the help they can get. For the young males, you can think of them as live-in helpers who get their food and accommodation covered. The young males don’t have the ability or resources to strike out on their own and start their own families. So, in the meantime, they’ll help the main social pair - and get to live in their territories, too.
It’s easy to tell which Fairywren is male (a brilliant blue) or female (a slightly more dull brown, with a rusty eyemask). This species is notable for its marked sexual dimorphism - I’ll make a whole other newsletter on this topic (and my favourite, most sexually dimorphic birds) another day!
Greater Vasa Parrot
Greater Vasa Parrots are native to Madagascar and nearby islands, and have a very unusual breeding biology and mating system. (Trust me, you won’t be ready when the reveal comes up.)
Females are 25% larger than males and are physically dominant - okay, that’s nothing special. Most female hawks, owls, falcons, and eagles outsize their male counterparts.
The species lives in loose polyamorous groups wherein each female has at least three to eight (8!) sexual partners - okay, that’s a little more surprising, but like the example of the Superb Fairywren shows, not unheard of.
The males have re-evolved a phallus, and sexy time can last up to 90 minutes because their penises get trapped within the female. Yup - there it is! This is unusual (of the 10,000+ species of birds in the world, only around 3% of them have a penis. And for both bird and human copulations, 90 minutes per sexy time … is a long time.)
Copulations come in two varieties, short duration (1–3 seconds) and long duration (averaging 36 minutes), which usually involved something called a copulatory tie: it refers to when the two birds are unable to part during sexy time due to the swelling of the male’s penis within the female. Ouch.
It seems a common theme amongst promiscuous birds is their need for survival (although I have no idea WTF is going on with the Greater Vasa Parrot, other than the fact that they make for great fodder for this newsletter). Don’t judge a bird too harshly for sexually promiscuous behaviour!
Thanks again for reading until the end! :)
WOW the male fairywren is stuntin. So cute that they're legit called SUPERB fairywrens