From Kendeigh (1941).

1994, Paradis et al. 1998, Winkler et al. 2004). Typically, within species, mean adult dispersal distances are about one half of natal distances, but in some species only one sixth as great (Table 17.3, Figure 17.5). The majority of adults nested close to where they bred the previous year.

Such patterns are again evident in a wide range of species, including passerines, raptors, game birds, shorebirds, waterfowl and colonial seabirds, both resident and migratory. For example, in the Northern House Martin Delichon urbica studied in some German villages, the median dispersal distance between natal and first breeding sites was found to be 75 m, whereas for breeding adults moving between nesting sites of different years, the median distance was 35 m. Some 7% of adults returned to the same nests in successive years (Rheinwald & Gutscher 1969). Within species, differences between age groups may arise largely because, each year when nesting begins, older birds are first to establish territories, or are better able to compete for them, so that the later settling youngsters then have to search over wider areas to find vacancies. The alternative, that young birds show poorer navigational skills, seems unlikely because the age differences in dispersal distances occur in resident, as well as in migratory populations.

For some species, more detailed studies have revealed patterns in the year-to-year territory fidelity and territory changes of breeders. Five main patterns have emerged: (a) sex differences in site-fidelity within species, with males in most species more likely than females to stay on the same territory from year to year,3 possibly related to sex differences in territory acquisition and defence; (b) a tendency for greater site-fidelity in later life,4 possibly related to increasing benefits through life of site-familiarity; (c) a greater tendency to change territories after

3Examples: Greenwood (1980), Gavin & Bollinger (1988), Payne & Payne (1993), Jackson (1994), Murphy (1996).

4Examples: Newton (1993), Harvey et al. (1984), Thompson et al. (1994), Aebischer (1995), Lemon et al. (1996), Morton (1997), Bried & Jouventin (1998), Forero et al. (1999), Winkler et al. (2004).

Table 17.3 Dispersal distances (km) calculated from recoveries of birds ringed and found dead in Britain, 1909-1994


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