Although 90% of all bird species stay with one partner for at least part of a season, there are many that have more than one partner. In this article, I look at some of the different ways polygamy is put into practice and the reasons why many birds practice it.
Not as common as monogamy in birds, there are still many polygamous species. There are two types of polygamy in birds. Polygyny is when the male breeds with more than one female, while polyandry is when the female has more than one partner.
Although this may be known as cheating in humans, this occurs in birds for many reasons. If you want to know why, please read on.
Do you want to know why birds stay with one partner? I have written this article here
What is polygamy?
Polygamy occurs in birds when either the male or the female has several mates in the same breeding season. While many species stay together for at least part of the season, polygamous birds do not create a pair-bond at all with their partner.
There are two types of polygamy. Polygyny is where the male has multiple mates, and polyandry is where the female has many mates.
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Of the two types of polygamy, polygyny, where the male breeds with more than one female in the season, is more common.
There are two types of polygyny. Simultaneous polygyny is when the male has impregnated several females simultaneously, possibly having eggs in several nests.
Serial polygyny occurs when the male helps to incubate the eggs and rear the chicks before moving on to the next breeding opportunity.
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Females are attracted to males with the best physical condition, plumage, displays, and songs. Males that attract the most females will live in areas safe from predators and have an ample supply of food. This is called location-defence polygyny.
By marking out an area that is safe and has a good supply of food, males are in the best condition. Females can see this from their plumage, song, and displays and will check on their territory. If the place is safe from predators, the male is fit enough to defend its territory. A promising sign for a female wanting to breed. Once they see that it is safe and a good place to raise their young, they will want to breed.
The male will attempt to attract as many females to the areas by defending a large territory.
The males generally do not help in incubating and raising the chicks, but they may build the nest. I am often asked why the females would put up with males that do not help, but the answer is quite simple.
Raising the chicks on their own without the male’s help is made a lot easier because of the abundant resources around them. Even with two birds raising the chicks, raising them in areas with low amounts of food and many predators is much more difficult than in areas with plenty of food.
Monogamous relationships in areas with low food resources and high predation rates have a much lower fledging success.
Red-winged blackbirds will return home about a week before females to establish their territories. Males with the best territories (food and safety) can attract up to ten females, while others may have none come to their territory.
Although a good supply of food is essential for the survival of infants, some species look for other things in a territory. Bobolinks look for the amount of vegetation that covers an area, as do Lark Buntings, with areas with excellent coverage attracting the most females. In areas that can be extremely hot, this makes perfect sense as the foliage stops the chicks from getting too hot and dehydrating.
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Another type of polygyny is called female-defence polygyny. This type of polygyny happens when males fight for an established collection of breeding females and defend them against other males. This provides the female with security.
Again, males do not look after the young or provide any parental care in this instance.
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Breeding areas, called leks, are formed in areas with a high density of males of certain species. Bustards, Whydahs, and Indigobirds all form breeding leks.
Leks are generally areas with few resources and occur in many species, including gamebirds, manakins, birds of paradise, and waders.
Females will visit the leks and defend a small area to preside over the males. Four or five males will often make a courtship or breeding display for the female. The most dominant male will take the centre of the area, called arenas or courts.
Males may stay in leks for weeks or months, but females will only stay for a few hours until they have mated. Males, especially those that are fit and healthy and show the best displays, may mate several times over the breeding season.
It has been noted that many females in these leks will often choose the same male to breed, with studies showing that 10% of males will do three-quarters of the mating. Although they may all look similar to us, the females see or hear something that shows them the male is going to give them the best success at reproducing.
Birds that hold leks are generally more elaborate in their displays and often have crests, tails, and ruffs larger or more colourful than other birds.
Once the female has chosen their mate and has mated with them, they will move to a different location to nest. Males do not help with the incubation or raising the young. Because they need to raise their young alone, they need to produce a small clutch of eggs. Birds that mate in leks are usually precocial, and in birds where food is easily found, such as fruit. Some birds are also brood parasites.
Leks often occur because food resources are spread over large areas, so these birds cannot defend a specific area to welcome a female (location polygyny). There will also not be many females in one place (female-resource polygyny.)
Leks are often safer from predators for both the male and the female. Males will try to compete to impress the female, and the areas can get very noisy.
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While polygyny occurs when males have more than one female mate, polyandry is when females have more than one mate. Although this does happen, it is much rare than polygyny.
Spotted sandpipers, Jacanas, and some Phalaropes are all polyandrous species. Polyandrous females are usually much larger and more colourful than males.
Polyandrous females will mark out areas with a good food supply and are safe from predators. The female will protect the territory and find food for the chicks while the male will incubate and raise the chicks.
Because the female saves energy from not incubating the eggs, they often lay more clutches at eggs, ensuring that her genes are passed on.
Polyandry occurs typically in areas with more males than females. Polyandry also happens in areas of high egg predation. Being able to lay many clutches of eggs at once allows the female to ensure that a good amount of young survive.
Because the female can be selective of their partner, the male will help. The male will incubate the eggs and look after the chicks even if the female flies off as he has no choice but to ensure that they survive, even if he knows they may not be his.
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