Factors Influencing Numbers of Syntopic House Sparrows and Eurasian Tree Sparrows on Farms
382 ShortCommunications and Commentaries [Auk, Vol. 110 The Auk 110(2):382-385, 1993 Factors Influencing Numbers of Syntopic House Sparrows and Eurasian Tree Sparrows on Farms PEDROJ. CORDERO InstitutoPirenaico de Ecologœa,Consejo Superior de InvestigacionesCient•ficas, Apartado202, 50080 Zaragoza,Spain The House Sparrow(Passer domesticus) and the Eur- was mappedand classifiedinto agriculturalland, in- asianTree Sparrow(P. montanus)show differencesin cluding: (FORAGE)orchards, cereals and associated habitat use. The former is predominantly an urban natural vegetationwhere sparrowsforaged; (FOR- and suburbanspecies, while the EurasianTree Spar- EST)woodlands, including Mediterranean oak, pine row is more rural (Summers-Smith 1963, Pinowski forestand Mediterranean scrub;and (GARDEN) gar- 1967, Lack 1971, Cody 1974, Dyer et al. 1977). How- dens, including groves of several tree speciesand ever, they often coexistalong suburban-ruralgradi- ornamentalshrubs where the sparrowsdid not forage. ents (Cody 1974), where extensivediet overlap (An- Open fields supportedagricultural activities, mostly derson1978, 1984) and nest-sitesegregation (Anderson intensivevegetable growing (89%),with the rest in 1978,Cordero and Rodriguez-Teijeiro1990) have been alfalfa, wheat, barley and maize. found. Some ecological(Pinowski 1967, Anderson To evaluate livestock I considered cattle equiva- 1978)and geographical(Summers-Smith 1963, 1988) lents of domestic animal biomass (LIVESIND; Table evidence suggeststhat habitat differences,in part, 1). To obtain this, total
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