Wednesday, 2 May 2007

Black Terns grace Livermere lake

As I noted last month, Livermere Lake sits within a very open landscape, just over the county border towards Bury St. Edmunds. It has a reputation for attracting unusual waterbirds, including many passage migrants, and a visit in late April or early May can be particularly rewarding. Just the other day I was fortunate enough to see both my first little ringed plover of the year and my first black terns. The terns certainly stole the show. Playfully pitching about in their characteristic, almost erratic, flight, they frequently rose and then dipped down towards the water’s surface. These small, compact birds, short-winged and tailed, are marsh terns – distinctly different in appearance from the larger, more familiar, Sterna terns (like common, arctic and sandwich), which are more commonly seen.

The black tern can best be described as a fairly common passage migrant, seen across eastern counties during spring and, to a lesser extent, autumn. While the last of the spring passage birds may be seen in Norfolk as late as mid-May, the first autumn birds can appear just a few weeks later at the beginning of July. The spring birds will have travelled up the Atlantic coast of Africa and Europe from coastal wintering grounds in Senegal, the Gambia and Namibia, while others will have turned right through the Straits of Gibraltar to enter the Mediterranean and then head overland across continental Europe. All of the birds will have been heading for breeding areas within Eastern Europe and the former Soviet Union. Historically, however, many would have headed to Eastern England to breed in the Fens and the Broads, a pattern that no longer occurs. Writing in 1668, Sir Thomas Browne noted how the black tern was ‘common about Broad waters and plashes not farre from the sea”. One particular area of alder carr near Upton was home to many hundreds of pairs in the 1600s. Unfortunately, this particular colony disappeared soon after the introduction of the 1799 Upton Drainage Act. Drainage of the favoured wetland areas no doubt played a major part in the demise of this bird but the more direct actions of Man were also contributory. Egg-collecting was rife and the last Nineteenth Century nesting attempt (Sutton Broad, 1858) ended when the eggs were stolen and the adult birds shot. Just over 100 years later, four pairs nested at Welney but because of falling water levels none of the young survived. The last successful nest was also at Welney (in 1975), a poignant reminder of a breeding species effectively lost from our much-changed countryside. There are occasional records of over-summering birds and, with the establishment of new inland reserves, it is just possible that we will see further nesting attempts in the future.

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