Close Encounters of the Owl Kind

Nick Carter,  Wetland Project Officer

I paid my first visit of the year to the Wissey Wetland on Wednesday and had an immediate surprise. As I drove down the entrance track a short-eared owl flew across in front of the vehicle. I stopped and thought I might get a decent flight image but the bird then very co-operatively landed the other side of the ditch running alongside the track. It allowed me to get very close and take some of the attached images. The bird obviously spied something flying over at one point, which I didn’t see. 

Short-eared owls have been recorded occasionally on the Methwold and Hilgay sites before but this gave the best views.  After visiting the very wet Hilgay site and checking all was ok I saw a barn owl which I wasn’t able to photograph. However the short-eared owl was still hunting around the access track quite near the entrance so I stopped to watch it. I then realised that there were two short-eared owls hunting. So a nice welcome to the site for 2016 and another surprise on leaving it.

Reed warbler link

Nick Carter, Wetland Project Officer

Reed Warbler, by Chris Thornton

Kartong Bird Observatory, at the southern end of the Gambian coast, was established in 2010 and so far 12,000 birds, including 256 reed warblers, have been ringed there. Ringing takes place in the reedbeds that have developed in an old sand mine and also in the surrounding Acacia scrub. L930934 was ringed there on 18 January 2014 and I have just been informed by the BTO (which licences bird ringing in the UK) it was re-trapped on the Hilgay Wetland Creation site, a joint venture with Environment Agency, on 11 August 2015, a distance of 4,647km and a gap of 1 year and 205 days. She is a female and had an active brood patch when trapped which means she was breeding onsite. Of the reed warblers ringed at Kartong, six have been re-trapped in Europe but the Hilgay bird represents the furthest north of any of these recoveries.

Numbers of reed warblers are increasing on the Hilgay site as the areas of reeds enlarge with three pairs present in 2014 and up to eight pairs this year. Most of them are concentrated on the reed-filled ditch on the northern boundary of the site although some birds were singing in the southwest corner of the site this year. It will take several years for the reedbeds to develop fully and obviously reed warbler is one of those species that will benefit enormously. Ringing on the site will not only enable us to monitor this population increase but also important breeding parameters as breeding success by comparing numbers of young and adults ringed each year.

Curing the bank erosion problems at Hilgay

Nick Carter, Wetland Project Officer
 

Bank erosion

One of the main tasks last winter at Hilgay was to fill the storage lagoon in stages up to the maximum level 1.59m above sea level. During the filling process the banks had to be checked to ensure there were no leaks or subsidence. The filling passed without incident but then the maximum level had to be held for at least a month while the checking continued. It was during this month, with the water at the same level, that wave action resulting from the south westerly winds caused some bank erosion along the northern banks of the two arms of the lagoon. The sandy soils prevalent in the area and the poor grass establishment added to the problem.

The erosion matting

A plan was hatched to solve the problem by using erosion matting over a layer of peat sown with a grass mix. The peat would ensure good growth of the grass which would help strengthen the integrity of the bank. At the bottom of the matting a line of reeds would be planted that would grow to form a natural barrier that would break up the action of the waves to reduce the erosion pressure. Fen Group was employed to deposit peat from the Methwold site, where they were already working, along the two eroded banks, 75-100m in length. The grass mix was sown and the two sets of erosion matting were laid over the top and pinned down in position. Well-developed reeds were sown by Broadwood Conservation, who had done reed planting on the Hilgay and Methwold sites this year, and then protected by chicken wire cages to prevent grazing by the resident wildfowl.

The grass has germinated in the mild conditions we have had so far this autumn and is becoming established through the erosion matting. The cages appear to be working in protecting the young reeds which should establish, which combined with the natural vegetation that has developed along the lowered shoreline should protect the bank. Water levels will be raised gradually during the winter to ensure the grass and reeds have the maximum time to develop while temperatures are still mild. The matting will prevent any erosion this winter and as it rots away it will be replaced by the hopefully well-established grass sward and the fringe of reeds.

Biocontrol of Water Fern

Nick Carter, Conservation Officer (Fens)

Water fern in storage lagoon

Water fern, Azolla filiculoides, a native of Central and North America was introduced into the UK in about 1840 as an ornamental aquatic plant but has since spread into the wider environment. It can quickly form dense, thick mats of green or red vegetation that block out light, cause de-oxygenation of the water, kill aquatic flora and fauna and interfere with water management. It spreads vegetatively - making mechanical control impossible - and by spores in the autumn.  

It was first noticed in autumn 2012 in the storage lagoon at Hilgay but following the cold winter of 2012/3 it was not noted in 2013. It reappeared in autumn 2014 again in the storage lagoon either from survivors of the original infestation or re-introduction by wildfowl. It grew rapidly to form dense mats which survived the winter and spread to other parts of the site in 2015. The warm weather during June and July resulted in the formation of dense mats again.

Stenopelmus rufinasus adult,
photo by Corin Pratt CABI

Natural help is at hand however in the form of a tiny, native North American weevil, Stenopelmus rufinasus. It was first recorded in the UK in 1921, presumably being present on imported water fern plants. It is considered by Defra (Department for Environment, Food and Rural Affairs) to be ordinarily resident so there are no licensing requirements to release populations where they are not present naturally.

CABI (Centre for Agricultural and Biosciences International) is a not-for-profit organisation which develops solutions to agricultural and environmental issues and is a world leader in the development of biocontrol solutions. It rears the weevil and we have recently bought and released several batches of it in order to get it established at the site before the winter.  As the weevil feeds exclusively on water fern there is no risk to other plant species and is thus a very specific control measure, an advantage over more broad-spectrum chemical control measures.

We will monitor the situation in 2016 to check that the weevils have survived the winter and do further introductions if it looks as though the water fern is getting out of control again. In the longer term it is hoped that the permanent presence of the weevil on site will keep the water fern distribution in balance so dense, extensive mats do not form.

Methwold & Hilgay updates

Nick Carter, Conservation Officer (Fens)

The fine weather and the all-clear on the archaeology side have meant that construction work by Fen Group is progressing well at Methwold, the joint project with Environment Agency to provide compensatory reedbed. 

Perimeter bank and ditch, photo by Nick Carter

The perimeter bank and ditch, installed as a flood-defence measure, should be finished this week. It is interesting to compare the very sandy soil in this area with that over much of the rest of the site, which has the deep peaty layers. This higher, drier sand island was inhabited by Neolithic people. Simultaneously work is progressing with the main reedbed embankment. Soil is being moved across the site from deep pools to form the key trench below the embankment and its inner core. The deep pools will act as fish refuges and also provide the vital edge between open water and reed that bitterns favour for feeding. 

The first of five water control structures has also been installed. This will control the flow of water between the two main reedbed compartments. The work has to be completed by the end of October and so we are hoping the fine weather continues to enable the work to proceed without delay.

On the Hilgay site the breeding season for some species still seems to be in full swing while for others the autumn migration is underway. The five pochard ducklings are growing well and are now nearly as large as their mother and I also saw four tufted duck broods, including the one with 10 young. 

Great crested grebe and young, photo by Nick Carter

Two pairs of great crested grebes have young while a third pair is still on a nest, as are several pairs of little grebe. The black-headed gull colony is still very noisy and there is a range of ages of birds present. The avocet pair has one remaining chick out of a nest of four eggs while lapwings have finished breeding and have flocked up, with over 80 on site this week. Three ruff remain and redshank, oystercatcher, little ringed plover, green sandpiper and greenshank are still on site. At least 19 little egret were around too and herons were still busy feeding on the site.

Waterfowl fest at Hilgay

Nick Carter, Conservation Officer (Fens) 
 
A brief visit to Hilgay in early July came up trumps with migrating waders and breeding duck. 

A

Ruff group, photo by Nick Carter

t least 10 male ruff, moulting out of their finery but still stunning, were present in the lagoon area. As usual the variation in colouring between the different males made you think they were different species with some predominately white, others dark and even a few red ones. On occasions they flew around as one group but when feeding often spread out.

There was also greenshank, green sandpiper, oystercatcher, a small flock of lapwing, two avocets and redshank onsite. Later in the week another observer saw 20 ruff and 10 black-tailed godwit. In birdwatching terms the autumn migration is now in full swing!

Brood of tufted duck, photo by Nick Carter

The brood of five pochard young are still present with a noticeable growth of the youngsters. Nearby a brood of 10 tufted duck is also present, although the ducklings are younger than the pochard ones. There is still one well-grown great-crested grebe present and plenty of young coot and black-headed gulls around.

Breeding ups and downs at Hilgay

Nick Carter, Conservation Officer (Fens)

Pochard with young, photo by Nick Carter

Two new bird species have been confirmed as breeding at Hilgay; great crested grebe and pochard. The former was first noted on the lagoon during the 2014/5 winter with up to six birds being noted in the spring. In early June one well-grown young was observed with its parents and later that month an active nest was observed. Small numbers of pochard were noted through the winter too. Then in mid-June a female pochard was noted with five very small ducklings, also in the lagoon. Pochard is a scarce breeding resident so this is a great record for the site. Both species have benefitted from the filling of the lagoon over the 2014/5 winter which has provided them with the deeper water these two diving species need. Several other duck species are also present: shelduck, mallard, teal, shoveler, gadwall and tufted duck but only mallard has produced young so far.

A thriving black-headed gull colony has also established in one of the rushy compartments. At least 200 birds are in the colony but it is not certain if they are all breeding and in mid-June at least nine young were seen swimming around the deep pools.

Wader productivity has not been good this year with lapwing, redshank, oystercatcher, avocet and little ringed plover attempting to breed but with few resultant offspring. The hoped for return of the sand martin colony to the sandy ditch sides which had been tidied up failed to materialise although a few birds were seen in the spring.

A record 19 little egrets were seen together in June, with probably other birds spread around the site. There is a small heronry close to the site but there is no evidence of any little egrets breeding there yet.