Thursday, 29 July 2010

Pilsey Island 29th July.

As we arrived on Pilsey Island an Osprey drifting over, carrying a
mullet back for lunch, was a good start to today's site visit. The
excellent vegetation included Lax-flowered Sea Lavender, Long-bracted
Sedge, Sea Holly and Sea Heath. Few seabirds had nested here this
year though, with regular disturbance in this busy part of Chichester
Harbour being a likely reason.

We continued round and out into Langstone Harbour, where there was a
different story. This year, the islands supported 400 pairs of Med
Gull, 205 pairs of Sandwich Tern, 81 pairs of Common Terns, and most
significantly, the 61 pairs of Little Tern had reared at least 47
young. 'Recharge' of the islands with gravel (to increase their
height above high tides), combined with some predator control, has
helped produce an excellent season. Disturbance is less of an issue
here. However, the Med Gulls also appear to be part of the problem
for the terns. Whilst the adults rearing chicks seem to forage inland
for invertebrates, the failed and non breeders hang around the
colonies predating eggs and chicks.

As high tide approached, the wader roosts gathered; 500+ Curlews, 200+
Oystercatchers, and small numbers of Whimbrel, Dunlin and Ringed
Plover were noted.

Friday, 23 July 2010

Bigger is better

A super Bittern pic by Steve Blain, an old Bittern nest and Small Red-eyed Damselfly

The week marked the start of a period of work assessing the quality of many of the best reedbeds around the country. How are they performing for birds and Bitterns in particular? This largely involves wading through reedbeds getting wet, smelly, hammered by mosquitos and cut to shreds by reeds.

We started at Ham Wall in Somerset. More correctly, we started by looking for the nesting Little Bitterns. Sightings had now become infrequent as it appeared that feeding flights to the nest had stopped. There were two brief views of the female. However, sightings by visitors of ‘small brown bitterns’ in the vicinity suggested that the young have fledged.

Fifteen years after the reedbed creation started, Ham Wall now supports more Bitterns that any other UK reedbed - a remarkable success. This year there were 8 boomers and at least 8 nests, with a further 7 boomers in the wider area. This success is undoubtedly partly due to the size of the site. At over 200 ha, this is a large reedbed. It is clear that these bigger habitat creations are performing better than smaller sites. It is also a very wet reedbed, with around a metre or more of water in the reedbed areas chosen for nesting by the Bitterns. We record habitat details (water depth, reed height and density etc) around old nest sites in order to further our knowledge of replicating these conditions in new sites being developed.

Ham Wall is formed from ex-peat diggings, now restored to wetland habitat by careful land-forming. Fish and amphibian populations are now exceeding the threshold for Bitterns, hence the recent surge in breeding birds. This site now forms the standard that all others have to match.

A number of Bitterns were seen during the visit, as well as Great White Egret, Bearded Tit, Marsh Harrier, many Cetti's Warblers and good numbers of Small Red-eyed Damselflies.

Thursday, 15 July 2010

Terning the tide

Gadwall brood and Draper scrape with Garganey

Rye Meads is a highly productive site for breeding waterbirds, ducklings seemed to be everywhere during my visit today, with a minimum of 15 broods of Tufted Duck, 7 of Pochard and 11 of Gadwall scattered around the various lagoons. The Draper scrape also produced a juvenile Garganey, a Shelduck, 2 Green Sandpipers and a Common Sandpiper.

However, it was the Common Tern colony that was the main reason for the visit. They have been squeezed off their rafts by Black-headed Gulls in the last 2 or 3 years. This year the totals appear to be 19 pairs of terns to 21 pairs of gulls. The gulls have been very productive, the terns have not, only six tern chicks were visible today. How to provide for the terns in the face of the advancing gulls is a management dilemma at the moment, with a variety of ideas to be trialled over the next year or so. Elsewhere in the Lee Valley, terns are doing well, with productive colonies at Amwell and Cheshunt (although only 2 pairs of BHGs are nesting at the latter site). Competition between terns and gulls is commonplace around the coastal colonies, with terns having minimal productivity or being completely ousted at some sites. However, inland on tern rafts, this is a new and growing trend. These tern colonies have traditionally been very productive. Time will tell if they continue to be so.

Sunday, 11 July 2010

Scrapes - a rant!

Vange Marsh - a scrape in good condition.

So why is it that most reserves can’t seem to manage a decent wader scrape over a period of time? They start off good but then fade away. We have all seen muddy pools that pull in loads of birds and probably all lamented the lack of birds on some established reserve’s wader scrape. So what is it that makes a scrape perform or not?

Food abundance and availability are the key issues, and these are affected by water regime, nutrient levels and predators. New wetlands are generally highly productive in the first few years of existence as early colonising invertebrates benefit from high nutrient levels and reach high abundance levels. Food! As time passes, nutrients become locked up in the system in mud and decomposing material and invertebrate predators increase as a more balanced system develops. Less food!

So the key is to dry out shallow water bodies to allow nutrients to be released to the system, to kill off predators and then to re-set the clock by allowing re-colonisation. But how often should this be done? Some ‘food’ invertebrates may peak in year 1, others up to years 4-5. The trouble is that birders then moan when a scrape is dry for a season and there are no birds. Many reserves fail to manage scrapes correctly for fear of a visitor backlash when they are dry, but then end up with a visitor backlash for having few birds.

This week I visited a few scrapes, most were crap! Rainham had a very few birds, (including the White-tailed Plover) but notice they rarely stay. The best was at Vange Marsh ; 125 Black-tailed Godwits, 7 Spotted Reds, 5 Greenshank and good numbers of Green and Common Sands.

Wednesday, 7 July 2010

Turf and surf

Fen Orchids

Sutton Fen has been claimed to be one of the most biodiverse and untrodden parts of England. On a sunny June day it seems a fair claim as Swallowtails and Norfolk Hawkers zipped around and exposed limbs attracted a wider range of clegs and mozzies than normal. We were visiting Sutton to review the management for Fen Orchids. A good number were in flower as we wandered around pontificating on the finer points of orchid ecology and realising how little we actually knew. The population is doing well, with an estimated 700 spikes. It seems the orchid may have different strategies for different conditions. In dry years the seed pods may split and disperse the seeds as normal, but in wet years the seeds may be retained, and germinate in the pod the following year, or may be released to be dispersed by water. The role of animals or people in disturbing the ground and moving seeds is unclear. Although few people visit in recent years, this site would have been heavily managed for fen products in the past. This decline in 'disturbance' is likely to have led to the orchids decline. One method of restoring this ‘disturbance’ is to cut shallow ‘turf ponds’ where the fen vegetation is set back to the early succession state favoured by the orchids.

The following day we were down on the Suffolk coast at Dingle Marshes. Standing on the shingle ridge it soon becomes clear this is, as opposed to Sutton, one of the most trodden parts of England. The coastal pools looked good however; 2 Spoonbills, 8 Med Gulls, 7 Dusky Redshanks, numerous Avocets and an early returning Golden Plover were the star birds. However, the few nesting Little Terns are struggling despite the habitat looking good. Although fences have been put up around the colony, there is a conflict; in general people do not like fences on their beaches, and this is a major problem for Little Terns. Numbers are declining all around the coast as they a struggle with a lack of habitat, increased attention of predators, and wave after wave of holiday makers.