A report on
the 2002 breeding season
at the
Little Tern colony
Martin G Stoyle
September 2002
This project was sponsored by BP Exploration, English Nature and the South Holderness Countryside Society and was managed by Spurn Bird Observatory Trust
2. Summary
3. Acknowledgements
4. Weather
5. The Little Tern colony month by month
6. Historical breeding success
7. Wardening and visitors
8. Reserve management
9. Protection against predators
10. Predators
11. Ringing and colour ring sightings
12. Discussion
13. Other
bird species at Beacon Lagoons Nature Reserve
For many years, the Little Tern Project at Easington has made a significant difference to the success of the colony. Within the UK, BP Exploration views projects, such as The Little Tern project, as small but positive steps towards conserving our unique national biodiversity. It is one of many projects that BP supports both onshore and offshore within the UK, helping to contribute towards the national strategy for biodiversity.
These initiatives are at the international, national and local levels and are becoming increasingly reliant on partnerships between governments, local interest groups and the private sector. Lord John Browne, CEO of BP, has committed the company to action on biodiversity;
“We can have a real, measurable and positive impact on biodiversity of the world. That is a high aspiration – but like our other aspirations we’re determined to show that we can deliver” (27th April 2000)
Traditionally, biodiversity has been treated as a local issue relating to the ‘footprint’ of our operations, emissions and secondary impacts. However, accelerating population growth and development pressures are leading to an increasing loss of biodiversity and calls for a more strategic approach to conserving what remains. In response to the increasing problem, BP Exploration in the North Sea is dedicated to developing a Biodiversity Action Plan (BAP) for all its key facilities. The process of developing a BAP has centred around five strategic themes;
1) Conservation projects – to create collaborative partnerships, fund and contribute to conservation activities aligned with local, national, regional and global priorities.
2) Responsible operations – to understand our direct and indirect impacts on biodiversity and demonstrate continual improvement in our performance.
3) External relations – to understand what is important to people and form partnerships to develop solutions to biodiversity issues
4) Research, education and awareness – to make a positive contribution to biodiversity research and education and to raise the awareness and understanding of our employees, the people we work with and our customers
5) Public policy contribution – to contribute constructively to public policy debate on biodiversity.
Through the implementation of these 5 themes, BP aims to live up to the high aspirations set by the group and to help local projects in the areas that we operate.
The results of this years project are hugely encouraging for the future of the
Little Terns at Easington and hopefully, with the help of BP, the project and
the Terns will thrive for many years to come. However, the Little Tern project
at Easington would not be a success were it not for the dedication of the Spurn
Bird Observatory Trust and BP Exploration is proud to be able to support this
hard work through one of the most successful years in the projects history
Mike Brock – Environmental Advisor, BP Southern North Sea
2. Summary
The first Little Terns arrived back at the colony on the 19th April and display was in progress at the start of the Wardens contract on the 28th April. Numbers built up reasonably quickly throughout May to a maximum of 115 on the 25th May with most birds nest prospecting by this date. Then, inexplicably, nearly all birds left the area, leaving just five birds on the 28th May. The first eggs were being incubated by the 30th May.
The first eggs hatched on the 18th June and the number of incubating pairs built up gradually to 28 by the 27th June. Human disturbance was light for the vast majority of the time and this combined with the fine weather prevalent for most of the month looked conducive for a successful breeding season.
At the beginning of July six pairs re-laid, and more chicks were hatching on daily basis. Fox tracks were seen regularly though no evidence of predation was found. The first chicks fledged on the 21st July, and by the month end 17 fledged juveniles were counted roosting on the beach. Activity in August remained surprisingly high given the late date. On the 10th 29 fledglings were on the beach. Another 3 chicks fledged on the 16th August, giving a total of 32 fledged juveniles from 34 pairs.
This was the best year at Easington since 1999, and our equal third highest productivity per pair ever recorded.
3. Acknowledgements
Many thanks to BP Exploration for providing the funding that made the scheme possible in 2002. Thanks must also go to the South Holderness Countryside Society for their support and to Spurn Bird Observatory Trust for managing the project.
Once again Craig Ralston of English Nature and York University BTCV group helped with the erection of the perimeter fence, which was greatly appreciated. Last, but not least thanks must go to stalwart volunteers Frank Kennington, for helping with wardening and Barry Spence, for ringing the chicks.
4. Weather
April A strong southwesterly wind was prevalent from the start of the Warden’s contract until the month end.
May A southerly wind on the 1st gave way to a moderate northwesterly until the 11th. The wind remained southerly and light for the rest of the month.
June A force 2-3 southerly wind prevailed during the month.
July A strong northwesterly wind on the 2nd, gave out to light variable winds for the rest of the month.
August The wind remained mainly from the south or variable all month, with very little rain.
5. The Little tern colony month by month
The first Little Terns arrived back in the area on the 19th April, with at least 20 Terns showing the first signs of display on 20th. The Warden’s contract started on the 28th and Tern numbers fluctuated for the next few days, with 23 birds displaying over the colony on the 31st, a very encouraging sign for the coming months.
May started off in much the same way that April had finished with Terns increasing to 25 on the 1st and staying around this figure until the 10th. The next week saw numbers increase dramatically on a daily basis with 40 birds on the 11th increasing to 80 by the 15th, many of which were displaying and nest prospecting in and around the colony. By the 20th the colony was a hive of activity with 115 Terns displaying and nest scraping within the traditional breeding area. The situation stayed like this for the next week and expectations were high that the first pairs would soon be laying and incubating.
On the morning of the 27th it was amazing to find most of the Terns had made a mass exodus prior to the Warden’s arrival that morning, leaving only five birds present. The reasons for this are only speculation at this stage, though one interesting point is that they were not using their preferred food item, the Sand eel, during courtship, which possibly indicated a lack of this food source.
The first pair was incubating by the 30th, though disappointingly the number of birds still in the area totaled just five birds by the month end. This was a disappointing conclusion to the month.
The 1st saw another Little Tern incubating, though well to the south of the traditional breeding area, where it was offered no protection from terrestrial predators, so the chances of the eggs surviving appeared to be slim. Tern numbers in the area were still low but had increased to 15 by the 3rd and on the 4th another pair had laid in the traditional breeding area. Terrestrial predator tracks (Stoat, Weasel and Fox) were seen all around the colony during this period, though no evidence of predation was noted.
On the 8th the Terns outside the main breeding area had their eggs predated, probably by two Carrion Crows that were frequenting the southern end of the reserve. On the 9th another pair of Terns were sitting in the traditional breeding area and on the 10th another pair was found to have laid to the south of the breeding area, though upon inspection was found to only have one egg, probably indicating a first time breeder; It was later discovered that the egg was unfortunately addled. The 12th saw the first encouraging sign of the month, Sand eels were now being caught offshore by the breeding Terns. Within hours another 30 Terns were displaying on the beach, and in the afternoon a minimum of 200 Sandwich Terns arrived at Beacon Ponds, where there had not been any earlier in the month.
The number of incubating pairs was now increasing on a daily basis, rising to 18 by the 18th, when unfortunately a clutch of eggs was lost to a territorial Oystercatcher that had laid near a sitting Little Tern. The first chicks hatched on schedule on the 19th. On the 21st another pair was found to have lost their eggs overnight, this time to a Stoat/Weasel. This pair had however laid outside the electric fencing that is used for keeping out terrestrial predators. Another two chicks hatched on the 25th.
Human disturbance was light throughout this period and predator tracks were seen less frequently towards the end of the month. The only concern was that the hatched chicks did not seem to be getting fed very often and when they were it was not with Sand eels. The main food source seemed to be Shrimps and small Sprats, at least until the end of the month.
July
On the 1st the number of breeding pairs reached 28. The 2nd dawned with a strong northwesterly wind and heavy seas, which caused concern for the safety of the chicks and also the incubating adults. Luckily no losses occurred, either through blown sand covering eggs or the sea washing into the colony. On the 4th more chicks hatched and were regularly fed with Sand eels, which had suddenly become readily available. The light predation, kind weather and now good feeding offshore made for good breeding conditions.
Over the next seven days more chicks hatched, and apart from a brief appearance by a male Kestrel on the 7th, which was easily driven off by the pursuing adult Little Terns, disturbance was relatively light. On the morning of the 11th a Roe Deer was found to have knocked the electric fence down during the previous night and Fox tracks were visible within the colony, though actual predation, if any, seemed to be minimal. The 12th saw an overnight incursion of a far more malicious nature. A large length of wood had been used to flatten the electric fence so a number of people could enter the colony, though again it was hard to ascertain just how much damage to the colony had been caused. On the 13th it became obvious that whatever the motivation for the previous days incursion had been the damage caused had been thankfully light.
By now plenty of chicks were being seen and the vast majority of incubating birds had young. The actual counting of chicks was virtually impossible as most chicks were in the dunes, an area that is not visible from any of the Warden’s observation points. Another worrying factor was that in the evening a large number of chicks were wandering onto the beach outside the protection of the electric fence.
On the morning of the 14th a large number of Fox tracks were found around the electric fence and few chicks were seen. The situation continued like this for the next five days. Plenty of chicks were obviously still present, as adult Terns were dropping into the dunes with food, although it is feared that the mortality rate from Fox predation was quite high.
The morning of the 20th dawned with heavy rain, which made counting impossible until mid-afternoon when the rain eventually abated. It was great to find 6 almost fledged juveniles sat near the lagoons. Over the next ten days more chicks fledged, leading to a maximum count of 17 fledged juveniles by the end of the month.
On the 1st two Merlins arrived in the area. This did not bode well for the remaining unfledged chicks, and indeed by the end of the day at least one chick had been predated.
By now the only way to get an accurate count of fledged juveniles was to count them roosting on the beach at low tide. By the 4th the number of fledged chicks totaled 27. A few pairs of late laying Terns still had chicks that were only just over two weeks old and due to the now exceptionally late date the chances of survival for these chicks seemed very low. Terrestrial predator tracks were now abundant in the area and up to three Merlins were regularly seen around the reserve. Amazingly the number of fledged birds climbed again to 29 by the 10th. The next week saw most of the unfledged chicks being predated, mostly by the Merlins and the vast majority of Terns had now left. Incredibly on the 16th 3 newly fledged juveniles were found in the colony. These were the last birds to fledge from the colony in 2002, and increased the final total to 32 juveniles from 34 pairs.
This year represented the best breeding success at Easington for four years (see Table 1).
Table 1: Breeding Success of Little Terns at Easington 1986-2002
|
Year |
No. of pairs |
No. of fledged young |
Productivity, chicks fledged per pair |
|
1986 |
22 |
5 |
0.23 |
|
1987 |
2 |
0 |
0 |
|
1988 |
3 |
4 |
1.33 |
|
1989 |
20-25 |
1 |
0.04 |
|
1990 |
31 |
29 |
0.94 |
|
1991 |
20 |
0 |
0 |
|
1992 |
34 |
11 |
0.32 |
|
1993 |
62 |
20 |
0.32 |
|
1994 |
65 |
29 |
0.45 |
|
1995 |
71 |
4 |
0.06 |
|
1996 |
49 |
31 |
0.63 |
|
1997 |
41 |
2 |
.0.05 |
|
1998 |
41 |
42 |
1.02 |
|
1999 |
54 |
45 |
0.83 |
|
2000 |
49 |
9 |
0.18 |
|
2001 |
44 |
3 |
0.07 |
|
2002 |
34 |
32 |
0.94 |
6. Wardening and visitors
Most daylight hours were covered either by the Warden or small group of volunteers. The public in general caused little disturbance to the Terns. There were only two incursions into the colony during daylight hours, both of which were by people who claimed to have not seen or to have misinterpreted the warning signs. These incursion issues were always resolved quickly once the situation was explained.
7. Reserve management
The perimeter fence that surrounds the reserve during the breeding season was erected on the 28th April and taken down on the 24th August after the Terns had dispersed from the area. The main function of this fence is to act as a visible deterrent to the general public and used in conjunction with breeding bird signs. This dramatically reduces the number of incursions into the breeding area by the public.
The electric fence that surrounds the traditional breeding area was erected on the 23rd May and removed on 24th August. The main function of this fence is to protect against terrestrial predators, such as Foxes, which mainly hunt at night when the reserve is unmanned. It also helps to keep people, who have inadvertently wandered into the boundaries of the colony, out of the main breeding area.
8. Predator protection measures
Once again an electric fence was erected around the main breeding area. This is to protect against terrestrial predators such as Foxes. No Little Tern losses were thought to occur to terrestrial predators within the confines of the electric fence during the 2002 breeding season.
During the 2002 breeding season three different types of chick shelters were used.
9. Predators
The following ground and avian predators were recorded in, or near, the colony during 2002.
Red Fox Vulpes vulpes
Fresh tracks were found on a number of occasions throughout the breeding season and they certainly predated a number of chicks, although because they hunt mainly at night their exact impact is unknown.
Stoat/Weasel Mustela ermina and M. nivalis
Stoat or Weasel tracks were found on a number of occasions and they are believed to have predated at least one clutch of eggs during the 2002 breeding season.
Grey Heron Ardea cinerea
This species never posed a really serious threat to the colony, but whenever one came near they were mobbed constantly until well out of the area. No losses were due to this species during the 2002 breeding season.
Kestrel Falco tinnunculus
Only one sighting of Kestrel was noted during the 2002 breeding season. Thankfully no losses occurred to this species in 2002 unlike 2001.
Merlin Falco columbarius
Up to three birds were present towards the end of the breeding season. These predated at least one chick, although possibly took many more.
On several occasions many Terns were seen mobbing an unknown predator that was probably this species.
Oystercatcher Haematopus ostralegus
One clutch is known to have been predated by birds breeding within the area of the colony
Barn Owl Tyto alba
One or more birds were regularly present around the Long Bank area during the breeding season. They seemed to pose no threat to the Little Terns and prey items observed were always small voles. Fortunately they never found the easy source of food only a few yards away and no losses were due to this species during the 2002 breeding season
Carrion Crow Corvus corone
Up to four birds were present throughout the season, mostly frequenting the Long Bank area. Any birds straying into the colony were quickly seen off by the Little Terns. They predated one clutch of eggs during the 2002 breeding season.
10. Ringing and colour ring sightings
A total of 27 Little Tern chicks were ringed using the Easington colour rings (mauve). These were placed on the left leg with a standard BTO metal ring on the right leg. All visits into the colony were covered by Schedule 1 licenses issued by English Nature.
Colour ring sightings
Two pairs of colour ringed birds from other colonies nested at Easington this year providing numerous sightings throughout the season, these were a pair with red rings on their left legs and a pair with blue rings on their left legs.
Other sightings were as follows: -
20th May Six birds with blue rings and one with a red ring.
22nd May One bird with a black ring.
25th May Five birds with blue rings
Key to Little Tern colour ring colours
|
Colour of ring |
Location where ringed |
|
Mauve |
Easington and Spurn, East Yorkshire |
|
Red |
Tetney and Gibraltar Point, Lincolnshire |
|
Blue |
Teeside |
|
Black |
North Wales |
|
Green |
Norfolk |
11. Discussion
There was a drop in the number of breeding pairs from 44 the previous year to 34 in 2002 the lowest number for ten years. It seems possible that the decline could be due to poor breeding success in a number of previous years. Another reason could relate to a lack of their preferred food, Sand eel. Birds observed displaying were not using this food source prior to leaving in May. Terns did not return to the area until Sand eels reappeared offshore. Reasons for this food not being available are unknown. Were the Sand eels at a deeper depth and so inaccessible to Little Terns? or is Sand-eel harvesting in the North Sea beginning to have an effect on breeding seabirds? More investigation needs to be carried out to determine if Sand-eel stocks are low and identify the causes for the decline.
12. Other birds at Beacon lagoons
The following species of bird, which are listed as Birds of Conservation Concern (BOCC) by the RSPB, were also recorded at Beacon Lagoons during the project.
In addition to breeding birds, Beacon Lagoons are also an important area for roosting waders, terns and wildfowl whilst on passage.
Shelduck Tadorna tadorna
Up to 5 birds were seen regularly until the end of May. Shelduck is a BOCC on the Amber list (BL, WI, WL).
Teal Anas crecca
A flock comprising of 19 birds was noted on the 31st July on Beacon Ponds. Teal is a BOCC on the Amber list (WI).
Kestrel Falco tinnunculus
Only one sighting of Kestrel was noted throughout the Little Tern breeding season. Kestrel is a BOCC on the Amber list (BDMp, SPEC 2or3).
Oystercatcher Haemontopus ostralegus
Five pairs bred within the reserve boundary, with the maximum number of passage birds peaking at 62 on 16th August. Oystercatcher is a BOCC on the Amber list (BI, WL WI).
Grey Plover Pluvialis squatarola
Good numbers of Grey Plover were seen throughout the 2002 breeding season, with a high count of 287 on 19th June. Grey Plover is a BOCC on the Amber list (WI, WL).
Dunlin Calidris alpina
Small numbers were seen on passage in May. Autumn passage migrants were noted from early July, building up to a peak of 10,000 by late August. Dunlin is a BOCC on the Amber list (WI, WL, BDMr, BL, SPEC 2or3).
Ruff Philomachus pugnax
Several summer plumaged males were present throughout July involving at least 10 different birds. Ruff is a BOCC on the Amber list (BR, WL).
Bar-tailed Godwit Limosa lapponica
A maximum count of 132 on the 2nd August. Bar-tailed Godwit is a BOCC on the Amber list (WI, WL, SPEC 2or3).
Redshank Tringa totanus
Regularly seen roosting on Beacon Ponds from early July with numbers exceeding 8000 towards the end of August. Redshank is a BOCC on the Amber list (WI, SPEC 2or3, WBMp).
Sandwich Tern Sterna sandivencis
Large numbers roosted on Beacon Ponds from mid July, with up to 3000 present on most days in August. Sandwich Tern is a BOCC on the Amber list (BL, SPEC 2or3).
Sand Martin Riparia riparia
Up to 300 birds regularly fed around Beacon ponds throughout July. Most birds involved appeared to be juveniles indicating good breeding success in the nearby area. Sand Martin is a BOCC on the Amber list (SPEC 2or3).
Skylark Alauda arvensis
Eight pairs nested within the reserve boundary. Skylark is a BOCC on the Red list (BD).
Tree Sparrow Passer montanus
Up to 30 birds were seen regularly at the northern end of the reserve. Tree Sparrow is a BOCC on the Red list (BD).
Linnet Carduelis cannabina
Nine pairs bred, and up to 83 birds were regularly seen at the northern end of the reserve. Linnet is a BOCC on the Red list (BD).
Reed Bunting Emberiza schoeniclus
Five pairs bred fledging a minimum of 9 birds. Reed Bunting is a BOCC on the Red list (BD).
Corn Bunting Miliaia calandra
Six singing birds were present around the reserve, with at least 3 pairs breeding. Corn Bunting is a BOCC on the Red list (BD, HD).
RSPB Birds of Conservation Concern (BOCC)
Red list criteria
BD = >50% decline of the UK breeding population, or range, over the previous 25 years.
HD = Historical population decline in the UK between 1800-1995.
Amber list criteria
BDMp = a moderate decline (25-49%) in the UK breeding population, or range, over the previous 25 years.
BR = five year mean of 0.2-300 breeding pairs in the UK.
WI = >20% of European breeding population in the UK.
BL = >50% of the UK breeding population can be found in 10 or fewer sites, but not BR.
WL = >50% of the UK non-breeding population can be found in 10 or fewer sites.
SPEC 2or3 = species with an unfavourable conservation status in Europe.
BDMr =moderate (25-49) contraction of UK breeding range over last 25 years.