Great Northern Diver (Gavia immer)
Great Northern Diver
Status: A widespread winter visitor to coastal areas from September to April.
Conservation Concern: Green-listed in Ireland. The European population has been assessed as Secure.
Identification: Great Northern Divers are large and powerfully built. The heavy, spear-like bill is held in a horizontal position when birds are on the water. The head is large with a steep forehead and a crown that is usually flat; but can be raised forming a bump- like crown. During the winter the bill is grey with a dark tip and birds have a prominent pale eye-ring and a dark half-collar on the lower neck. In summer the head and bill darken becoming black and the upper body plumage takes on the distinctive black and white chequered and spotted pattern.
Similar Species: Red- throated Diver, Black-throated Diver, White-billed Diver, Great Crested Grebe, Cormorant, Shag.
Call: Mainly silent over winter, contact call is a loud moaning sound rising slightly
Diet: Mostly fish but also feeds on crustaceans, molluscs, annelids, insects and amphibians.
Breeding: Age of first breeding: not known. Great Northern Divers do not breed in Ireland. The closest breeding birds are in Iceland and the breeding distribution spreads east through Greenland to North America.
Wintering: Great Northern Divers occur along the Irish coastline between September and April and are usually observed as single birds or small groups. They are the most numerous of the divers occurring in Ireland and are particularly abundant off the south, west and northwest coasts over the winter. Great Northern Divers occur along a variety of coastlines, particularly deeper bays and inlets, as well as shallow bays with sandy shores. They can forage up to 10 km offshore and numbers close to shore tend to be highest when winds blow onshore.
Where to See: Three sites hold internationally important numbers of Great Northern Divers- Inner Galway Bay (County Galway), The Mullet Peninsula (Co. Mayo), Donegal Bay (Co. Donegal). Four sites hold nationally important numbers - Courtmacsherry Bay (Co. Cork), Wexford Bay (Co. Wexford), Wexford Harbour & Slobs (Co. Wexford), Castlemaine Harbour (Co. Kerry).