Wednesday, 22 April 2015

New Tern Raft

Today we launched our old tern raft and another brand new one.

Alf Peacock, Matt Hall, Mike Thomas and Roy Mathers.
Last year we did not put our raft out on the water until May simply because we hadn't finished building it. It turned out to be  a good idea to avoid gulls using the raft as they were already settled in on the Sailing Lake islands.

This year the gulls are nesting a mile away and the first pair of terns we saw seemed to spend all day on the mooring buoys waiting for us to put their raft back. Of course we can't prove they are the same terns that nested there last year, but we think it is possible.

In fact, I have a theory about these common terns: I think that these individuals may have hatched on a tern raft somewhere else and therefore associate these man-made islands with nesting, rather than the slightly more natural islands that all the other terns are using.

Next stop, Antigua!
Breeding on a raft is better than on an island because of the lack of competition and predation. The perspex walls help to make them more predator proof and terns will nest very close together, often in less than a square foot per pair!

Both of our rafts were built for us by Alf Peacock using a galvanised steel frame and large polystyrene blocks as a basis. The Friends of Paxton Pits Nature Reserve paid for them and they were put in place by volunteers led by ranger Matt Hall.

But what about the terns themselves?

At this time of year, several species of terns are on migration to their northern breeding grounds. Of the so-called "marsh terns" that breed near fresh water rather than salt, we are most likely to see black terns and common terns. Arctic terns look almost identical to common terns but they nest further north and winter further south. They also prefer salt-water locations. All three species have been seen in the district this week.  Other species can turn up, but you have to be there when they pass through. I can remember whiskered and little terns popping by Paxton Pits.

Common tern (RSPB).
Common Terns are really miss-named; they are outnumbered by Arctic Terns, both in the UK and globally, but they "tern up" in urban areas where people can see them.

While Arctic terns hold all the long-distance migration records, British Common Terns are not to be sneered at with most of them wintering from Ghana in West Africa through the Gulf of Guinea and down to the Cape.