Disturbance: The colonial nesting habits of Little Terns in areas such as sandy or shingle beaches has meant that they are prone to disturbance from the recreational activities of humans & dogs. The immediate threat involves the unintentional trampling of the well camouflaged eggs & chicks. Furthermore, when a human or a dog enters the colony, the adult terns will take flight (often calling loudly & dive bombing the 'intruders'). Prolonged spells of disturbance during wet & very warm weather can result in eggs failing to hatch or even the death of chicks through overexposure. During periods of disturbance, Hooded Crows & gulls can also learn to take advantage of the unguarded nests & will make raids on the colony to steal eggs. The abandonment of a former breeding site at Dollymount Strand, Bull Island, Co. Dublin by the Little Terns is the most obvious case in Ireland of the effect that increased recreational use of beaches can have on these birds.
An example of how easy it is to trample a nest © Dick Coombes
Natural Predators: With all the hustle & bustle going on at a breeding tern colony it is no wonder that from time to time they will attract the attention of natural predators. Eggs can be taken during the day by Hooded Crows and at night by Red Foxes & even Hedgehogs! Other species such as Rook, Lesser Black-backed Gull & Brown Rat have also been recorded taking eggs. Little Tern chicks present a more substantial meal for potential predators. At night they are vulnerable to predation by Red Foxes & American Mink whilst during the day, Kestrels seem to target 2 week old birds, which are just about the right size for them. Adult & fledgling Little Terns are also predated by Birds of Prey such as Peregrines & Sparrowhawks. In 2006 an adult Little Tern at Kilcoole was even observed to have been taken by a Hobby!
Adult Little Tern incubating its eggs © Michael Finn