Sunday, February 11, 2001		Nature

ALL animals, including birds, defend their territory very fiercely, but European white wagtail sometimes gives up its territorial rights in a good year when there is sufficient food in the area for itself and perhaps one other bird. The intruder is not allowed to feed free of cost instead it has to help the resident bird in warding off other birds who try to intrude. But if the situation changes and the food is not all that easily available as it was before, the tenant is evicted and has to survive by stealing.

When the situation becomes harder still and the shortage of food within the birds’ territories reaches a critical stage, then all the boundaries are broken and they become flocking birds invading places where they can find food.

Found worldwide, wagtails are members of the pipit’s family which has 54 species, many of which are migratory. These thin and slender-billed birds are of small to medium size. These birds have long bodies and are found in different colours, including black, grey, yellow and brown. Some of them are also streaked. Inhabiting grasslands and open country, often near water, members of the family have fairly long legs with long hind claws. Feeding mainly on insects, these birds have a long tail which is usually edged with white or buff, which most species wag up and down. They build their nests on the ground.

It is believed that these birds first probably evolved in Africa. Even today, they are known to be the birds of open country. Some species like the golden pipit still have homes in the Savannah grasslands.

As far as territory is concerned, it is an area which is very important in the life of every animal. They are not land hungry. In an ideal world this space, which we call territory, would be precisely geared to the satisfying of their food requirements and no more. It makes no sense to expend energy in defending more territory than one needs. So when an animal occupies a larger territory than is usual for one of its species, it is almost certainly because its dietary requirements in that area are scarce.

Animals living in deserts tend to have larger territories than those living in more fertile regions. But even within the same ecosystem, different species have vastly different spatial requirements.

Territory not only provides food for an animal, it may help to keep pairs together by compelling birds to stay in their area. Territory may also be important because it provides a sense of security. In adult grouse, for example, homelessness can produce a fatal shock. Ousted from their familiar feeding ground by their developing young, older grouse will stop eating and, as the winter sets in, die. This is either because being weaker and more exposed on the wind-swept moor, they fall easy victims to predators, or as often seems to happen, they simply lose interest in living.

It has also been observed that a pair living in an area does not sing, mate or build a nest even during the breeding season — it means they do not possess any territory. In the case of rufouscollard sparrows of North America intruders, having no territory of their own, sneak into somebody else’s territory and remain as inconspicuous as possible, awaiting some fatality to overtake one if not both of the resident birds. If it does, the ‘lurkers’ take over their territory and become its masters. According to animal psychology, any animal already established in territory has an edge over the one coming from outside. It has been observed that ‘lurkers’ usually get of the territory.

Some birds adopt different strategies to gain living space. They lie low in another bird’s territory and try to breed. It has been observed that homeless pairs of European tits sometimes wait for a resident pair to go through the territorial rituals, which include fighting off other birds, singing to announce possession, building the nest, patrolling the boundaries etc. After all this exercise the resident bird becomes less aggressive and starts devoting its time to incubating. This is the time when deprived birds sneak into the territory. They do not waste time, finding a suitable and safe place they build their nest and start laying and incubating.

It they are caught by the rightful owner — which they often are — they will be chased away. Still despite that risk intruders do stand some chance of success, in many cases it goes upto fifty-fifty.