Friday, 17 July 2009

Sandwich Terns struggle against Gulls

With this years' breeding season almost over at Rye Harbour, I thought it was time to archive some of my recent visits to the reserve. Although I don't know the official figures, there's no doubt there are plenty of young Black Headed Gulls, Mediterranean Gulls, Common Terns and Sandwich Terns fledged and safely on the wing.

Rye Harbour has had a successful breeding season and has bucked the trend again, as most Tern and sea bird colonies have had a catastrophic breeding season in 2009. Changes in water temperature and consequent knock-on effects through the seabird food chain have resulted in fishless seas. For the time being though, the Rye harbour fishery appears healthy - it takes no time to spot a flock of Sandwich and Common Terns feeding inshore principally on Shad (Horse mackeral) with little effort.

Another reason for the success of Rye is the undoubted man-made protection provided by the Sussex Wildlife Trust that the reserve has. Fox, Mink and Cats are all unable to penetrate the fencing that surrounds the reserve perimeter - egg and chick protection at ground level is assured from the land at least.

Perimeter fencing around the reserve is vital to the breeding success of the colony at Rye.

One last reason for the this year's success will be the benefit of generally fine to very good weather. My last four visits have all been on near cloudless days with brilliant cyan skies and, importantly for the Terns, very calm seas. As far as I know, there haves been no thunder storms to wash away chicks and eggs as has happened in previous years.

I have had two memorable twilight visits to the Crittal hide in late June/early July. The Sandwich Terns were in loose family gatherings and could be seen on the shingle pool edges. Most fledglings were in pairs, usually accompanied by one adult awaiting the second parent to return from a fishing trip. I arrived early evening - photography initially poor with the sun shining sharply into the hide. But this was more than made-up for by the sight and sounds of the Terns and Gulls so close-in.

There's no doubt that the Terns' fish-catch was bountiful that night: and it had to be, because as the sun began to go down and darkness descended, the fish-bearing adults found it increasingly hard to find the correct fledged offspring, often losing their fish to the gulls altogether. Let me explain a little better, mixed in with the Terns and sitting along the pool edge, were Black-Headed and Mediterranean Gulls ready and waiting to harry and chase any fish-bearing Tern unsure of its exact fledgling rendezvous.

Constantly and noisily begging, one of many fledged Sandwich Terns close-in at the Crittal Hide

Accompanying adults with fledglings also join-in with endless homing-in calls to the soon-to-return fishing parent.

Here is a typical fish catch return. In my 3-hour stay, I must have witnessed hundreds of Terns returning, like this one, after fishing only a minute before, close in-shore, dropping in to a crowded creche of young terns - magic!

A Black headed gull keeps a watchful eye on the Terns

A Mediterranean gull seemingly sitting quiet and vacant, who will lunge and grab the tern's fish catch at any opportunity

Typical view from the Crittal hide looking at part of the Tern colony. As darkness descends, it will play into the hands (wings?!!) of the piratical gulls.

As the night proceeded, it became clear to me that the Terns have just one sure chance of delivering a fish safely to its fledglings. Any sign of indecision - one search too many, or a stop on the pool edges - was an immediate signal to the terns to harass and steal. Black headed gulls chased the Terns in twos and threes reminiscent of their big cousins, the Skuas, and are able to chase and force the Terns to drop there fish-catch and consequently steal it.

As darkness descended the Terns, with the benefit of a high tide, continued to bring in fish in a brisk and relentless routine, often flying extremely close in front of the hide.

The activity and drama on the pool increased, with gulls squabbling amongst themselves with the stolen fish catch, and the young Terns desperately calling out to parent birds. Sadly, it was obvious to me that the Sandwich Terns were really struggling to connect in the darkness, despite the constant contact calls of parents and fledglings. Often the the gulls snatched the distracted terns' catch within inches of the bird finding its young. In human terms, it all seemed so unfair and quite sad to see!

Sandwich Terns in near darkness, calling to aid the returning fish-carrying parent

A Sandwich tern's parent swiftly drops into its family group to deliver the fish catch

A moment's indecision sees an instant chase from the gulls

The pursuing gulls fight over the Tern's catch. It seemed, as darkness fell, that every other returning Tern, whilst struggling to find its fledglings, lost its catch to the Gulls.

For me, on both of my recent trips to Rye, it was a wonderful and exciting wildlife spectacle. Here I was with George, the only two people in the hide with a front row seat to a wildlife drama! Happily for the Sandwich Terns, despite the fishing losses, the ease of a new catch, just a minute's flight out to sea, meant that tehir chicks were unlikely to starve. Indeed, a week on, the fledglings were beginning to take on the size and structure of the parent birds - see below.

Heading out in to Rye Bay, this young Tern will not return for several years, spending the winter and the next 2 years off the coasts of West Africa. It will return as a breeding Adult.


Wilma said...

Great all round photodocumentation of evening feeding time. I particularly like the action pics and the ones that show the evening light; I can almost feel that I am there.

Life in Egypt said...

Nice to see the gulls . born in Llysfaen Colwyn Bay. we used to get more than our fare share of them.
and the Quarry below our house was a haven for the nesting season. now I live in Luxor Egypt, I never see the gulls, but the Cattle Egrets kind of do the same thing, follow the plough so to speak, one of the last shots in my blog will show you what I mean,