Breeding Success of the Caspian Tern in Finland

Egg Size and the Egg Predatory Behaviour of Crows

“…comm. ; for related findings with terns see LEMMETYINEN, 1972;NISBET & DRURl, 1972;SOIKKELI, 1973). Moreover, if a gull's nest was preyed on, predation of the third (or smallest egg) would result in a minimal reproductive loss.…”

Status and Reproductive Success of the Caspian Tern (Sterna caspia) in the U.S. Great Lakes

“…One and 2 egg clutches were common in Lake Winnipeg, Manitoba ( O f Donoghue andCowanlock 1919, Evons et al 1970), California ( DeCroot 1931, Mller 1943)) Texas (Pemberton 1922), and Florida (Dunstan et al 1975). Clutch sizes of 2 to 3 eggs are common in the Great Lakes (Vanwinkle 1893, Ludwig 1965, this study), Washington (Penland 1976 ), and northern Europe ( Bergn~on 1953, Soikkeli 1973. We assume these differences reflect proximate condttions of food availability, as suggested by the variation in clutch sizes within the Great Lakes popl~lation, ( Table 3 ), rather than interpopulat ion genetic differences .…”

“…This is unlike gulls which do not begin full incubation until the clutch is completed (Lkent 1970) and experience some egg loss of the exposed eggs during laying and early incubation. No potential egg predators other than gulls and terns (Soikkeli 1973) were observed on the study islands.…”

“…For instance, during censuses each year, we found less than 2% of the total eggs or shells out of the nests; inclusion of these in calculations does not change the average clutch size to the precision we have indicated. Also egg loss due to egg predation by adjacent gulls or terns is minimal in Caspian Terns because this species begins incubation with the (Bergman 1913, Soikkeli 1973. This is unlike gulls which do not begin full incubation until the clutch is completed (Lkent 1970) and experience some egg loss of the exposed eggs during laying and early incubation.…”

“…Young produced by renesters were determined in 1977 only, by visiting colonies on 8 August. Counts represent accurately the number that will fly from the colony as few young die after 3 weeks of age (Soikkeli 1973, Penland 1976). Gull-tern interactions from 1975 to 1978, and species of prey delivered to tern chicks at…”