REDUCED AVAILABILITY OF REFUSE AND BREEDING OUTPUT IN A HERRING GULL (LARUS-ARGENTATUS) COLONY

We studied the reproductive performance of herring gulls (Larus argent atus) in an old stable colony in SW Finland. Over the period 1993-1997 , the colony decreased, and the garbage dumps the birds may have utili sed have all closed. This had an effect on the breeding performance of the colony when comparing the year prior to the closing of the last g arbage dump available (1996), and the following season (1997). It is c lear that the last-laid egg size decreased significantly between years , more eggs were lost due to predation, and fewer of the hatched young fledged. The quality (in terms of body weight) of hatching chicks (bo th first and last) was not reduced, but first chicks grew slower in 19 97. These changes are in agreement with predictions from other studies , and are likely effects of diminishing food resources. However, overa ll production was still good, and the birds seem capable of successful breeding without the presence of nearby garbage dumps.