Ninety percent of all bird species are considered monogamous
Every spring and summer birds all over the world will engage in exhausting and intense courtship displays, all vying for the best partner in town, doing their utmost to show why they should be the one. It’s not just the males that do all the work, as recent studies have shown, and after the act of mating has taken place that energy is often happily rewarded with new lives to carry on the family name.
But – look at what I’ve done there. I’ve assigned human emotionsand aspirations to birds, and there is little to no evidence that suggests birds feel any of the above: romantic attraction, happiness of a union, the joy of a loving family to nurture.
It’s certainly possible, of course, and the great maxim that the absence of evidence is not evidence of absence may apply here, and perhaps these themes are best explored in another post.
What we do know about bird relationships, however, is that they simply have to form to carry on the species, like all living things.
Once this fact is established, the manner in which birds propagate their species is therefore best referred to as a bond, rather than a relationship. Pair bonds form between a male and a female bird once courtship has been successful, and different bird species remain in bonded pairs for different lengths of time.
The success of a brood is so important that many factors influence how long that pair bond lasts, and of course each species will be existing in its own unique set of circumstances.
The primary aim of any bond is to produce fit and healthy chicks
Before we look at the types of bonding there are, we just want to mention we came across some wonderful field work during the researching of this article. It has long been thought that courtship displays and eventual mating took place randomly and without bias – birds performed and whosoever was the best dancer got the girl and then the second best and so on.
The world of bird study is riddled with obstacles, not least because they keep flying away, but one group of dedicated scientists in the zoology department of UK’s Oxford University has been studying the social interactions of a particular bird species since 2011, with a view to establishing whether personality determines pair bonding.
Using data sets on breeding patterns that have been meticulously gathered since the 1970s, the group have been observing the resident great tits in Wytham Woods, which is home to 1019 bird boxes under constant scrutiny.
They have found that some birds spent a lot of time, months in some cases, foraging for food with their future partners, interacting and even giving up their food store when food was limited. This work has thrown up more questions along the way and the answers are still being sought but the research is fascinating, and if anyone wishes to read further, here is a link.
Ninety percent of all bird species are considered monogamous, that is, when they form a pair bond, that bond remains intact, or at least until breeding has occurred. This does not mean that all species will then “mate for life” – far from it, in fact.
Some species will have a second or even third brood with the same original partner, like most songbirds, but some will either change partners or not have another brood at all, such as wrens.
Ever wondered how do birds mate? Read more.
Veryfew species will bond with the same bird in the following breeding season, and from those that do, whilst this may occur for a number of years, pairs can “divorce” in the next breeding season for whatever reason, and potentially find another long-lasting mate the next year.
Bird societies are highly complex, and fathoming the whys and wherefores of bird bonds is life-defining work, so it is a great testament to the work of past academics that we know anything about these patterns at all.
Breaking up is easy to do
Romance is not on the list, here. The primary aim of any bond is to produce fit and healthy chicks. A partner considered able to meet that goal one day may fall short of implied expectations the next, and is therefore deemed to no longer have any value to the species.
The term divorce is indeed used when discussing bird pair separations. Divorce in the bird world is defined as having occurred when two birds who paired in one season are still alive in the next one, but one has chosen to mate with a new partner.
Established evolutionary theory suggests that once you’ve got it right, you should stay together to get it right again. A slight twist that appears to run against this line of thinking was discovered during research on plovers in 2019.
Successful pairs were seen to divorce almost immediately and find a new mate, whilst pairs who experienced nest failures stayed together to try for a second or third time.
It was found that the higher the divorce rate, the more offspring were produced, i.e., the more plovers who deserted the nest as soon as the eggs were successfully laid and found a new mate, the larger the population became.
One day I'll fly away
Large migratory birds such as geese, swans, cranes and albatrosses use a lot of time and energy going to and from their wintering and breeding grounds, so it is logical that these types of birds do form bonds that last for more than one breeding season – staying with one partner cuts out a lot of effort.
Courtship dances may still occur to reaffirm that bond, but often there is no one else getting a look in. Larger birds also reach sexual maturity relatively later than small birds, and often only have one brood as early into the season as possible, as they too will take a long time to grow. These birds can be considered as “mating for life” but if a partner is injured or dies then another partner will be sought.
Birds that need large territories in which to find food, like birds of prey, will pair for several seasons as it is simply too much effort to defend that sizable area and find a new partner each time.
The higher the divorce rate, the more offspring were produced
It’s not just the big birds who try to mate for life, though. If it were possible to add even more to their cuteness, Atlantic puffins reach sexual maturity after three years old and tend to keep the same partner, returning to the same burrow each season and share both egg incubation and parenting duties until one will die.
They also perform something called billing, when they rub their beaks together in what many can and do describe as an act of affection and companionship.
Whilst the cold hard science can state that birds don’t form emotional relationships like humans do, that their driver for forming a pair pond is to reproduce rather than for any romantic fulfilment, you try telling me that Wisdom, the 69-year-old (at least) Laysan Albatross who has had the same mating partner for over a decade, doesn’t see something in his deep, dark, heavily browed eyes.
That right there is love, and I’ll fight anyone who tells me differently.