A much nicer afternoon than morning, so after getting a whole load of College admin done before lunch I headed off to Cliffe pools with Monty. On the Radar viewpoint there were about 200 Black-tailed Godwits, 12 Little Egrets, 20 Redshanks, 3 Greenshanks (including the one-legged bird), 20 Great Crested Grebes, 15 Little Grebes, and some Black-headed Gulls. Across on the Ski Pool there were about 70 Shelduck, 49 Avocets and some Greater Black-backed and Herring Gulls amongst the Black-headed Gulls.
And then I saw a Black Tern over the back of the Ski Pool, noting the quite even grey of the uppersides, the grey breast smudge more visible in flight, the white forehead and black cap, and the slightly forked tail. I was also struck by the generally easy and steady flight, not making a lot of ground speed, quite bouncy and occasionally twisting and swooping down to close to the water surface and then back up again. I now think that it would have been taking insects from above the water surface, although at the time I thought that it was searching for fish and failing! This all ties in with its reported diet, mainly insects but also with small fish and amphibians on the breeding grounds and a mix of insects and fish on migration and on the wintering grounds.
After a while I trailed up towards the flamingo pool lookout, and saw the Black Tern again (unlikely I think to be a second bird), and this time it also settled on a distant rock at the near end of the Flamingo Pool.
On Flamingo there might have been another 30 Coots, 40 Great Crested Grebes and 30 Little Grebes. I also got a fleeting glimpse of an odd duck that might have been a Wigeon in eclipse.
A birder coming back from the Thames told me that there had been another half dozen black terns going West up the Thames. This seems to be a fairly typical movement for this species - I wonder where they are all heading for? Birds regularly migrate Westwards from Europe into England in the autumn (but are less regularly seen on the return trip). Presumably they then head South down the coast of Europe and perhaps the Atlantic coast of Africa to their wintering quarters along the Western African seaboard, centred in the Gulf of Guinea. Juveniles may often accompany them, but may not make the return journey for 2 or 3 years.
The Black Tern,
Chlidonias nigra, is spread across the Paleartic, with the nominate subspecies
nigra breeding in Eurasia and wintering in Africa, while the subspecies
surinamensis breeds in North America. They tend to be fairly gregarious and can commonly be found in groups of 2 - 20 on the breeding grounds or on migration. However they can also be found in much larger aggregations of up to thousands in certain migration points, or in Africa. Some birds may move South down the Nile and Rift valleys, perhaps wintering around the Sudan.
Spring migration of adults begins in late March, mainly via the West African coast. On reaching Spain many birds may move along a Mediterranean route while others follow the Atlantic coast, of which some may be seen in Britain. The "Sudanese" winterers come back up the Nile, and may join the main stream of migration as some of them on the Mediterranean route move Eastwards along the Northern coast of Africa before moving across to Eurasia.
The breeding grounds seem to be under some threat due to habitat loss, but the species is not declining fast enough to be considered threatened (by extinction). Interesting that the species can be declining and generally disappearing from specific areas, but not thought to be under threat! The birds arrive in a group at the possible breeding area, and explore it, finally settling to jointly build the nest - a pad of vegetation on the marsh or water or a scrape on the drier ground - and laying only about 3 days later. There are some great behaviours described in BWP, and overall it is a fascinating bird.
Courtship is primarily monogamous, at least for the current season. Courtship is both aerial and ground-based. There is generally only one clutch, of 2 - 4 eggs which take about 21 - 22 days to hatch. The young are precocial and nidifugous. They are fed by both parents (up to 80 times a day), and also brooded for the first week or so, staying in the nest itself for only 2-3 days, then wandering further as they explore the area around the nest site, and then heading off into the surrounding vegetation. They start to fledge after about 19 days and are capable of independent feeding and then flight from about 25 days old.
