Man-dependence of House Sparrows (Passer domesticus) in the Faroe Islands: habitat patch characteristics as determinants of presence and numbers

The House Sparrow (Passer domesticus) began to colonize the Faroe Islands in the mid-1940s and occurs in most built-up areas. Breeding is confined to the discrete human habitations (settlements) that form a pattern of patches ”habitat-islands”). In 2002 all settlements were surveyed and the number of pairs of parrows (total number ca. 2,700 pairs) and amount of vegetation (”green space”) were estimated. The settlements ranged in size from 0.01 km2 (a single farmstead) to 8.72 km2 (the capital) and 68% of them (n=118) were occupied by sparrows. Patch occupancy was positively correlated with both area and amount of vegetation (p < 0.001) but not quite with the degree of isolation (p = 0.15).
settlement with > 10 pairs (a possible source area) and topography (mainly mountains and open sea). The patch variables area, human
population, number of houses and houses were strongly intercorrelated.
Abundance (number of pairs) of sparrows was positively
correlated with the number of houses (r = 0.84, p < 0.001). In all
but one of the settlements with < 10 houses sparrows were absent,
and also in many of those with 10-60 houses where the scatter swas
wide (no significant correlation p = 0.25). All but one of the settlements
with > 60 houses supported sparrows and the correlation
with abundance was highly significant (p < 0.001). The absence
of sparrows in small settlements is discussed in terms of risks of
associated with small populations such as stochastic extinctions,
Allee effects, competition, and predation (incl. persecution by
Man). Various anthropogenic effects on abundance of sparrows
are discussed; e.g. age, type and conditions of buildings and the
presence of gardens, cultivations, and plantations all contributing
to shelter and food resources. The Faroese House Sparrow as a
metapopulation is briefly discussed.
The latter was crudely scored as a function of distance to nearest