Sunday, March 2, 2014

Communal roosting

White wagtail - Zakak Abjad - Montacilla alba
Communal roosting can be seen in several bird species. Every evening large numbers of birds congregate in a particular spot to sleep. Roosts can consist of birds of a single species or sometimes of mixed species. Most roosts are in trees especially in cities although some species such as gulls seek different habitats.

In Malta the best known communal roosters are the Spanish sparrow, the starling and the white wagtail. Spanish sparrows are resident and visit their roosts throughout the year although the number of birds visiting the roost changes with the season reaching a peak just after the breeding season when the population is at its highest.

Starlings and white wagtails winter in the Maltese islands. Both species are very common and can be seen throughout the winter even in urban areas. Starlings are noisy birds that often spend the day feeding on the ground in fields sometimes even very close to busy roads.

The white wagtail can be seen in built-up areas picking up insects and other small creatures from the ground. It is often very tame and can be approached closely before it flies away.   

Every year in early January a group of birdwatchers take up positions around the Valletta peninsula to count the number of white wagtails approaching the City to roost. Most of the white wagtails wintering in Malta spend the night in the large trees in front of the Law Courts and in St John’s Square in Valletta.
This year nearly 7,500 wagtails were counted approaching Valletta.

Communal roosting affords birds safety in numbers. A solitary bird sleeping in a tree stands little chance of avoiding being eaten by a predator but in a roost consisting of thousands of birds the chance of being eaten decreases by a factor of several thousands.

It is also believed that large numbers of birds roosting in a tree increase the temperature of their surroundings thus reducing the amount of energy they require to maintain their body temperature at an optimal level.

In some species communal roosting gives an opportunity to less experienced birds to follow older birds to good feeding sites thus saving time and energy.

This article was published in The Times of Malta on 15 January 2014

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