Pair shaped
VALENTINE’S Day has traditionally been thought of as the time that birds start to pair up, and many of them do just that during the month of February. Forming a pair is one of the most important things a bird can do, and if successful that pairing can last for a considerable length of time. It is estimated that 90% of birds are monogamous and so have a pair bond which can continue for a year or more, even for life.
Maintaining a successful pairing can be achieved with the help of bonding activities: certain behaviours which keep the connection strong. In most cases it is the male who undertakes the action, helping to reinforce his suitability as a mate. Different species have their own ways of doing this, and here are some of the more interesting ones.
Feeding is one way to cement a relationship and is seen as a part of courtship and pair maintenance in a wide range of birds from terns or kingfishers presenting a fish to robins with a worm. Most often the male will present food to the female, who sometimes begs for it in the manner of a youngster. Feeding a partner in this way has the added benefit of ensuring they stay fit and healthy – important for a female which may soon be laying eggs.
While seen among many garden birds, such feeding is rare among thrushes and seemingly absent in Common Starling. Perhaps the most spectacular form of courtship feeding is the aerial food pass, part of the courtship of many birds of prey, most notably harriers, Peregrine Falcon and Common Buzzard.
Mutual preening, or allopreening, is found among many bird species. A recent study identified 503 species from 116 families in which it had been recorded. The study showed that species which indulged in allopreening were less likely to divorce and also were more likely to share raising the young between both parents.
While such preening equates with tender caresses, it also has a practical function as it enables areas around the head and neck to get cleaned, something which no bird can do on its own. It occurs among several British birds including Northern Gannet, Eurasian Coot, Common Moorhen, auks, some gulls, Eurasian Dotterel, owls, pigeons, Common Swift, Common Kestrel, Swallow, crows and Magpie.
Related to allopreening is beak rubbing or billing – Puffins are well known for this. It often happens when a bird arrives back at the burrow, with one of the pair nibbling at the other’s beak, resulting in them starting to knock their beaks together noisily. Northern Gannets rub their beaks and ‘fence’ with them and many albatrosses behave similarly.
Many courtship displays continue after a pair has formed. Flight displays from some species can be seen while birds are nesting and dancing by Common Cranes will similarly be seen later in the breeding season.
Recent research had revealed that the personalities of male Great Tits affect pair bonding with potential partners and those birds which are most proactive will find a mate soonest and will spend more time with a partner strengthening the bond.
Some songbirds use their vocalisations to reinforce a pair bond and duetting can be part of this. Studies on some calls given by Zebra Finches to enhance their bond have been shown to directly trigger a receptor in the brain which also appears to be linked to allopreening. Chris Harbard