A condensed version of the following information can be found on this poster here - http://www.birdwatchireland.ie/Portals/0/pdfs/Little_Tern_poster.pdf
The Little Tern (Sternula albifrons) is the smallest species of tern in Ireland, with a body length of 22-24cm & a wing span of 48-55cm, making it roughly two-thirds the size of a Common Tern (Sterna hirundo).
|A pair of adult Little Terns, displaying all the relevant identification features © Michael Finn|
Status & Distribution
Little Terns are the rarest of Ireland’s five breeding tern species, with a population that fluctuates between 200-300 pairs from year to year. The colony at Kilcoole, Co. Wicklow is currently the largest in the country where 50-100 pairs regularly breed. Other large colonies on the east coast can be found at Baltray, Co. Louth & Wexford Harbour, Co.Wexford where up to 45 pairs & 90 pairs respectively have bred in recent years. Smaller colonies of 10-30 pairs exist on islands along the west coast in counties Kerry, Galway, Mayo & Donegal. The Little Tern is listed as an ANNEX I species under the EU Birds Directive and has been Amber-listed under the Birds of Conservation Concern in Ireland.
|Little Tern distribution in Ireland © BirdWatch Ireland|
Little Terns spend the winter off the west coast of Africa between Guinea and Cameroon, after which they migrate north to breed in Europe, arriving in Ireland from late April. Young Little Terns spend their first year in their African wintering quarters, returning to breed when 2 years old. Through ringing we know that the oldest Little Terns can live for up to 23 years. They feed mainly on sandeels (Ammodytes) as well as other small fish and crustaceans which are caught by plunge-diving.
|Adult Little Tern with a Sandeel © Michael Finn|
Following a period of courtship feeding & pair bonding, a clutch of two or three eggs is laid between mid-May & late-June. In Ireland, nesting typically occurs on sandy or shingle beaches, generally in small colonies of between 5 & 30 pairs. Numbers of breeding pairs present may be larger at sites where wardening is provided (such as at Kilcoole & Baltray). The nest is little more than a shallow scrape in the shingle or sand, in which they lay their well camouflaged eggs. The terns sometimes decorate their nests with shards of mussels & other pieces of debris. Little Terns raise only a single brood each year so pairs who lose their eggs early on in the breeding season may replace them, although later clutches are generally smaller (1 or 2 eggs).
|Little Tern nest © Niall Keogh|
The incubation period normally lasts around 21 days, although eggs may sometimes hatch after as little as 18 days of incubation. The chicks become mobile quite quickly and leave the nest scrape within 3 days of hatching. At Kilcoole, they are usually led down the beach towards the tideline by their parents, where they hide amongst the seaweed and other debris whilst waiting to be fed.
|Little Tern chicks at 1-2 days old © Niall Keogh|
When feeding conditions are favourable, the tern chicks can grow quite rapidly, doubling their weight in as little as 3 days. At approximately 2 weeks old, their weight begins to stabilise and energy is then invested in the final stages of wing strengthening & development. Chicks make their first attempts at flight when around 18 days old, but generally do not fully fledge until 25-28 days old. Soon afterwards they begin learning to fish for themselves, although they will continue to be fed by their parents for some weeks. The terns leave their colonies between late July & mid August. They migrate south to staging areas in Wexford Harbour & southern Portugal before making it back to their winter quarters by November.
|Little Tern chick at 8 days old, from the same brood as in the previous picture (Note the advances in wing, feather & bill development) © Niall Keogh|
|Little Tern fledgling at 23 days old (Note the remnants of fluffy chick down on its head) © Niall Keogh|