Some gull populations, particularly larger species in European and North American nature reserves, can have harmful effects on other nesting birds (sometimes rarer species of conservation concern) through competition for nesting space, food, and the predation of eggs and young. In some cases management to limit breeding gull numbers may be considered necessary.
A literature review was undertaken of the effectiveness of management techniques used to control gulls, especially on breeding grounds (focusing mainly on three large species, greater black-backed gull Larus marinus, herring gull L.argentatus and lesser black-backed gull L.fuscus, and one smaller species, black-headed gull L.ridibundus). Techniques were investigated with regards use at different scales, ranging from the control of individuals to attempted control of populations over large regions. The review also assessed damage caused by gulls (particularly towards other birds); this is not addressed in this summary.
A total of 44 relevant papers and articles were identified, primarily from the USA, Europe (UK, Sweden, Holland, Germany and Italy) and New Zealand. The following non-lethal and lethal control methods used were identified.
Limiting adults and immatures:
Eliminating gulls - cannon netting; trapping; catching at night; poisoning; narcotizing; shooting;
Scaring gulls - distress calls, noise machines, scarecrows;
Modification of habitat (breeding, feeding, loafing habitats).
Control via eggs and nestlings:
Removal of eggs/young - collecting of eggs and young; nest and egg removal; biological control; substitute eggs;
Egg sterilization - pricking; injection with formalin; shaking; spraying with or dipping into oil emulsion; embryonicide.
Shooting or trapping were found to be generally effective in the control of small numbers of gulls. Shooting is selective and very useful in the removal of individual 'rogue' gulls which are habitually destructive towards a protected species. Careful use of narcotic baits or poisons was identified as the most practicable means of control (if necessary and under strict licence only) where gulls nested in areas with few other species present; the advantage of narcotic baits over poisons is that some non-target species which have ingested them may have the chance to recover.
Where gulls nest in close association with other birds, other methods of control are required. If the area can be visited frequently through the breeding season, eggs and nests can continually be removed. If only infrequent visits can be made, injecting gull eggs to sterilize them was identified as a good method.
Several years of control may be required to reduce a gull population. There were no accounts of an effective method for reducing gull populations over large areas reported.
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