The paper contains a description of the measures taken at Copenhagen Airport to reduce the bird strike problem during the last 20 years. Apart from shooting and otherwise scaring away the birds, the ecological countermeasures are described. The measures at the island include spraying of the nests in the colony with an emulsion of oil and water with the result that the colony production of young birds has diminished. Further, it includes killing of the birds by use of alfa-chloralosis contained in tablets and put into dead herrings placed in the gulls nests. The result has been a reduction from about 37,000 pairs of herring gulls to less than 10,000 pairs of herring gulls breeding on the island. Approximately 100,000 US dollars are used every year to finance the different actions against the birds. The use of long grass has caused an increase in mice and as a result hereof an increase in kestrels involved in bird strikes.