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Swans Mate For Life

Swans mate for life, right? That’s a popular belief. But is it true? You read about it everywhere, so it must be true...?

Well, rather annoyingly, the answer is yes and no.

This section will deal with why swans do indeed mate for life (i.e. form a very long lasting pair bond) and the reasons for any eventual ‘divorce’.

Yes, They Do Mate For Life – Or At Least, For A Long Time!

If you ask anyone what they know about swans, you’ll hear a few things – they can break your arm (this is possible, but highly unlikely), they all belong to the Queen (not true) and lastly, that they mate for life.

Yes, they can mate for life, but that does not necessarily mean that all swans mate for life. It’s the same with people – some form a relationship with a partner that lasts from when they were teenagers until when either one of them dies. Some do, some don’t. It’s the same with swans.

The difference being that a far greater proportion of the swan population mate for life, than people. But they do ‘divorce’ and it’s not such a small amount as to be able to say that it’s insignificant. But the pair bond between swans is normally very strong.

The most ‘common’ situation which is thought to have been the reason for a swan divorce is the failure to breed successfully. The failure could be due to eggs not hatching, flooding destroying the nest, cygnets being lost, etc... but when this happens, there appears to be greater chance than normal that the birds will go their own separate ways and find another mate.

When this happens, it appears that the females are more successful in finding a new partner, than the males.

Where do they go to find another mate?

The females are thought to go back to flocks of swans that exist in her locality and find one there. The males do this too, but they are more likely to stay on in their current territory and hope to ‘charm’ a lone, passing female. This maybe why they’re less successful than the females; they will be fewer single females passing through the territory than there will be in a flock of young, unpaired-up birds.

The males don’t live as long either – frequent battles with other contenders to his patch, eventually takes its toll.

Although not really a ‘divorce’, if a pair was to lose one of its swans, the remaining bird will often find another mate, again, the female is more likely to be successful in this respect.

Even with no apparent reason, swan divorces still do occur. The numbers have been put at around 3% for swans that have successfully bred and around 9% for those birds yet to breed or have had a failed breeding season.

Non-Divorce Separations Do Happen

Although not a full blown divorce, I have known a pair of swans to separate for a short while and then reform the pair-bond.

When this occurred, I first thought that maybe the two birds had just got lost from each other and once they caught sight of each other, they would get back together straight away –however that was not the case.

I was walking the stretch of river where the two had formed a territory and successfully retained it for at least three years. Catching sight of the cob, I was expecting to find the pen just a short distance away. But she wasn’t there.

Instead I had to walk about a mile upstream, where I found her amongst a flock of young, non-breeding birds. She was in close proximity to the other swans, but not engaging in any courtship rituals or other interactions.

Eventually, she started to wander off downstream to the borderline between the flock and her previous home territory. There was a small gathering there of some of the swans from the field group having a preen and bathe. Watching them and the previously paired up pen approach, I saw her former mate, swim upstream, and very aggressively charge into the small gathering - by which time his separated partner was amongst them.

As he did so, there was a mad scattering of young swans, including the separated pen. He then charged at each one of the young pretenders, successfully seeing them off, but at no time did he do anything about the pen, formally his partner. He just completely ignored her, even though she was just as close to intruding on his territory as they were. He must have seen her, but gave no response, either positively or negatively.

After a triumphant shakedown and preen he was off back down to his usual area where he likes to hang out. The pen in the meantime kind of paddled around aimlessly at the top boundary of the territory letting out soft sounds, as if to call him, but there was no response, nor did she appear very keen to wander back into her former home range.

A few days later, I saw her tentatively swim down into the home range, all the while making those soft callings, but something spooked her a short distance in and she paddled rapidly back up to the safety of the field group’s range of the river, but she never interacted with them. It was as though she was only there because she felt she had nowhere else to go, see didn’t seem to want anything to do with the other swans present.

This went on for a few days until one morning I went into the territory only to find them both back together again. It appears that they had a temporary separation and then decided to get back together.

The story ends very happily because about a week later I find him proudly sitting on a freshly laid egg and about six weeks later, a beautiful pair of cygnets were born!    

Even Strange Pairings Last For Life

It’s not just the normal male-female, same species pairs that last for a long time, there have been some real deviations from the norm.

One of the most unexpected pairs I’ve heard of occurred at Copenhagen Zoo many years ago. Here, a male Whooper Swan and female Mute Swan formed a pairing for three years. When the female was exposed to a male swan of her own species, she showed no interest in him and stayed with her non-like species mate.

Other pairings and eventual hybrid broods include a Mute Swan forming a pair-bond with a Black Swan, with a resulting mixed species brood. The parents raised the cygnets as a pair in the normal way and did not display any interest in birds of their own species.

Homosexual pairings also occur. Two female Mute Swans have been recorded as successfully creating a long term pair-bond and then creating a nest and laying a subsequent clutch of eggs. The eggs were infertile, of course, so there were no hatchlings.

Male-male pairings have also been observed, too. At Abbotsbury, for many years they had a couple of cobs that used to go through a courtship process and built a nest every year, that they used to sit on. Obviously, there were no eggs, but they used to treat the nest site like it was the real thing. In addition to that, throughout the year, they used to hang out with each other, just like a normal male-female pairing would do.

Why Do Swans Mate For Life?

The answer to this question revolves a lot around the raising of the young and how it affects the birds individually.

It’s been my experience that female Mute Swans behave differently when paired up with another swan. In the presence of a male, they tend to be bolder, or at least, less shy and timid. They’re even said to be in better condition when they have a male nearby. The male’s presence allows her to feed more freely knowing that he’ll be around to afford her protection.

The males, by contrast, tend to be slightly less well conditioned when paired up. This is mainly because time will be spent protecting her and there may be more battles to fight, due to the fact that at certain times of the year, he’ll have a family to watch out for and that means defending a territory and keeping a watching guard over the cygnets to deter predators and other outside influences.

So, females experience a net gain as a result of the male’s protective qualities. But the main reason why Mute Swan pairings last so long is to do with the upbringing of the cygnets.

There is a long time between the start of nesting season and the eventual leaving of the resulting offspring. There’s a lot to be done; nest-building, incubation, brooding, protecting the young and leading them to food, etc... And these are more likely to be successfully carried out if there are two of them.

Incidentally, families that lose one of their parents often still survive because the remaining parent is able to do all of the tasks, but there will be an increase in the chance of failure because it will be more difficult to defend the territory and protect the young at the same time. It has been known for another unattached swan to pair up with the lone parent and bring the brood up as their own. 


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