Reduced availability of refuse and breeding output in a herring gull (Larus argentatus) colony

We studied the reproductive performance of herring gulls (Larus argentatus) in an old stable colony in SW Finland. Over the period 1993-1997, the colony decreased, and the garbage dumps the birds may have utilised 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 garbage dump available (1996), and the following season (1997). It is clear 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 (both first and last) was not reduced, but first chicks grew slower in 1997. These changes are in agreement with predictions from other studies, and are likely effects of diminishing food resources. However, overall production was still good, and the birds seem capable of successful breeding without the presence of nearby garbage dumps.

Kilpi, M. & Ost, M.1998, Ann. Zool. Fennici 35: 37-42