Little Tern Survey 2013
A record number of terns and other shore birds nested at the Outer Harbour in 2013. The shingle ridge is protected from walkers and dogs and attracted over 40 pairs of the rare Little Terns as well as a pair of the scarce Arctic Tern and many Common Terns. Unfortunately nearly all the Little Terns fell victim to a predator — read on to find out what we think it was, and for an account of the 2013 season's bird activity based on a survey by James McCallum.
In 2013 WHC commissioned bird expert James McCallum to carry out a monitoring survey on bird behaviour and breeding around the Harbour channel, for the fourth year. Although the survey was not required under the maintenance licence conditions for the channel dredging project, it provides comparison data to previous years. Here we report on what James found.
From the start of June to the end of August 2013, James carried out a survey of Little Tern breeding activity concentrating on the shingle and shell ridges to the east of the main channel on Bob Halls Sands and the Outer Harbour berm. The same methodology was followed as in previous years, however for 2013 observation time was reduced to one day per week. During the observations on Little Tern behaviour and breeding attempts, James also collected information on other nesting species such as Common Terns, Arctic Terns, Oystercatchers, Ringed Plovers, Blackheaded and common gulls.
Little Terns are a Schedule One breeding bird and are therefore legally protected. In order to avoid any disturbance to them on their nesting areas James watched them from a distance using a telescope with a 15 x 40 zoom lens. Little Terns have a black and yellow beak, a shrill cry and almost white wings. Weighing only 50g these birds migrate as far as West Africa in the winter — one ringed Norfolk bird was recorded in Senegal — and with just 1900 pairs in the whole of the UK, they are a closely protected species.
Wells Harbour Commissioners recognise the importance of the surveys which check for any disturbances caused by vessel movements or the channel dredger, Kari Hege. Both Little and Common Terns were noted as fishing in the channel when the dredger was working, and although neither species feeds closer than 90-100 metres, James reported that the dredger did not appear to trouble either species. It is good to report that terns are actively using the Channel and the Outer Harbour for feeding.
The 2013 breeding season started extremely well with the Outer Harbour berm, in particular, proving to be a very attractive breeding area. There was an impressive count of 41 pairs of nesting Little Terns which shows that the Outer Harbour site has developed into one of Norfolk's larger and most important colonies of this rare and threatened species. The 2013 survey also noted the first ever nesting pair of Arctic Terns and pair of Common Gulls nesting at the Outer Harbour site. The season was however dominated by high levels of natural predation and only a single young Little Tern fledged. Poor breeding success in 2013 was mirrored at most other sites along the north Norfolk coast.
This season Mediterranean gulls, a recent colonist, were thought to be responsible as the main predator. Between the morning of 22nd June and the evening of 24th June, it is believed that a predator, most likely to have been a Mediterranean gull, targeted the Little Tern colony at the Outer Harbour berm as there were no visible signs of chicks or eggs at the nesting areas. The majority of other nesting species were still present. A young Mediterranean gull was witnessed diving towards two pairs of displaying Little Terns on 26th June actively searching around the vegetation where the Terns had been resting and this bird may have been responsible for the predation. It was also twice observed killing and eating a Black-headed gull chick. But all was not lost as on 28th June a single recently fledged juvenile Little Tern was photographed on the Outer Harbour berm which came as a welcome surprise. Natural England indicated that all nesting attempts by Little Terns in neighbouring colonies had failed so the youngster certainly originated from the Outer Harbour berm.
The more exposed 'breeding ridges' (the Binks) on Bob Halls Sands were also hit by predation; initially by a fox and then later by gulls. In spite of high predation suffered by the Little Terns, the Common Terns at the Outer Harbour fared much better and successfully fledged 13 young.
James wrote in his notes: Tern Feeding behaviour - The feeding behaviour of the Little and Common Terns followed a clear pattern that mirrored the findings of the previous three surveys. As in 2012 the occurrence of trapped shoals of both Whitebait and Lesser Sandeels during ebb tides was also noted. The trapped fish quickly attracted the attention of both Terns and gulls. Whitebait were unusually abundant in Wells Harbour especially during the period mid July to mid August. Just before low tide shoals of Whitebait and Sandeels were frequently concentrated in shallow water by the falling tide. The gulls and Terns quickly identified this food source and large feeding groups frantically fed on the trapped fish until the supply was exhausted.
The following details the pattern of both Little and Common Terns in Wells Harbour. At high tide many birds are seen to be resting or small numbers fishing around The Bar or in the open sea. During rising and falling tide there is far more feeding activity, much occurring in the lower reaches of the channel (particularly on the eastern shore) especially around The Bar or in the open sea. Smaller numbers of both species may be seen south of the Lifeboat house. The Common Terns may be seen fishing as far up the channel as the Whelk Sheds and Little Terns regularly frequent the smaller creeks. The channel north of the Lifeboat House is, however by far the most important feeding area in Wells Harbour. At low tide the majority of both Little and Common Tern fishing activity takes place in the open sea. During the survey, Whitebait and Lesser Sandeels were the most commonly recorded prey items for both species.
Other species of birds were also recorded during the survey. The single pair of Arctic Terns which nested for the first time on the Outer Harbour berm had their eggs predated from the first nest and after they successfully hatched 2 chicks from the second attempt, these again were sadly also predated. Arctic terns are remarkable for making an annual migration of 80,000km all the way from the northern Hemisphere to Antarctica and back, and are a rare nesting species in the UK.
Six pairs of Oystercatcher were noted on Bob Halls Sands but failed to fledge any young, four pairs at the Outer Harbour fledged three young. Four pairs of Ringed Plover on Bob Halls Sands laid eggs but none fledged, four pairs on the Outer Harbour also laid eggs, one brood of chicks were seen but were thought to have been predated. Eleven pairs of Black-headed Gull laid eggs on Bob Halls Sands of which two pairs each fledged a single young. 108 nesting pairs were counted on a single day at the Outer Harbour with an estimate of 70 fledged young. Six pairs of Common Gull nested on Bob Hall's Sands but were all predated and a single pair nested for the first time at the Outer Harbour and fledged three young.
Wells Harbour Commissioners are confident that the results of the last four years surveys confirm that the Port's dredger Kari Hege and other vessel movements have no detrimental impact on the feeding or breeding activities of birds in the Harbour. The Outer Harbour has proved to be a more protective and productive habitat. It is imperative that birds breeding on the berm of the Outer Harbour are left undisturbed and the biggest controllable threat to this environment is disturbance by walkers and loose dogs. Wells Harbour Commissioners improved the protection of the Outer Harbour by erecting more signs in 2013, and wishes to thank everyone for their cooperation in keeping the area undisturbed.
It is easy to view the bird colony with a telescope or binoculars from the main footpath running along the sea bank, near the Pinewoods car park and cafe.
The full survey report can be downloaded here.
James McCallum is a wildlife artist living and working in North Norfolk. For information on his paintings and books, visit www.jamesmccallum.co.uk