THE HOUSE SPARROW PASSER DOMESTICUS: POPULATION PROBLEMS

Two problems of House Sparrow populations are examined: the influence of habitat on numbers and the variation in a population of House Sparrows throughout the year. Available data on censuses in Great Britain enable the population to be estimated as 10 millions; censuses from several parts of the bird's range suggest that House Sparrow numbers are correlated with the human population, the ratio being 1: 5. The seasonal variation in composition of a population is estimated from observations over five years on House Sparrows breeding on a group of seventeen houses together with breeding and mortality data obtained from British Trust for Ornithology records. The population reaches a maximum at the end of July when it is slightly less than double that at the beginning of the breeding season. It is considered that numbers are controlled by food supply and the colonial behaviour of the bird.