Reproductive effort of colonialand solitary breeding tree sparrows Passer montanus L.

A total of 250 nestboxes were arranged in five plots in a suburban area of Budapest, Hungary (19 deg 04’E, 47 deg 41’N). In each plot, 25 were placed at 50 m intervals to simulate solitary breeding and 25 3-5 m apart to simulate colonial breeding. Length of nest building period, feeding frequency, nestling mortality, nestlings’ diet, productivity and parental condition were compared for colonial and solitary breeding tree sparrows Passer montanus. Parents with long nest-building periods, including the majority of first-year females, produced fewer young than parents which built over short periods. Parents fed nestlings morefrequently and nestlings had lower mortality in second than first broods; whether or not a third brood was reared was determined by the costs invested in first and second broods. Females that laid a third clutch had reared fewer young in first and second broods and were heavier than females that reared many young in two broods.

Lajos Sasvfiri, Zoltfin Hegyi, Behav Ecol Sociobiol (1994) 34:113-123