Choice of census method
Table 9.1 lists the many methods that have been used for surveying birds. Though several methods are listed, there are broadly two types: those for species that are evenly distributed across the landscape; and those for species that are not (i.e. are highly clumped). Listing methods, territory mapping, point counts and transects, for example, are best for species that are evenly distributed (e.g. territorial species), whereas counts of colonies, roosts and flocks are best for species with clumped distributions. Do bear in mind, however, that the dispersion of a species may vary throughout the annual cycle. For example, seabirds often gather at breeding colonies in the spring, but are out at sea for much of the rest of the year. In contrast, manywaterfowl are distributed widely across the landscape while breeding, but commonly congregate outside the breeding season and are then much easier to count. Different methods would thus be required for different seasons, though it is often much simpler to count birds when they are clumped than it is when they are dispersed.