Abstract:
Several study areas were investigated at two Port Colborne
terneries during the summers of 1973 and 1974 in an attempt to
determine the influence of clutch size, time of clutch initiation,
position in the colony, proximity to Ring-billed Gulls, vegetation
and nesting substrate on the reproductive performance of the Common
Tern. Hatching success and reproductive success (the number of
chicks fledged per egg laid) were generally higher for 3-egg than
2-egg clutches but fledging (the number of chicks fledged per egg
hatched) success was usually independant of clutch size. Hatching,
fledging and reproductive success declined as a function of time of
clutch initiation. Mean clutch sizes also generally declined as a
function of time. Nests located in the center of the colony
exhibited higher fledging success than those on the periphery.
Rock-based clutches had a lower hatching success than clutches
initiated on sand or dried vegetation. Reproductive performance
did not appear to be related to proximity to Ring-billed Gulls
or vegetation within the study area.
