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 sparrows (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). The latter was crudely scored as a function of distance to nearest 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.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

Keyword

House sparrow

Passer domesticus

Faroe Islands

Publication and Content Type

kap (subject category)

vet (subject category)