Friday, 27 August 2010

Don’t blame the crows.

Redshank, Fox predating a nest at night, the fabulous Turov Marshes in Belarus.

I’ve spent too much time in the office recently. Today’s office was at Berney Marshes, looking at the results of this year’s breeding season for waders. On the face of it, it’s been a fairly good year with 157 pairs of Lapwing and 130 pairs of Redshank. However, productivity is the key issue and this was way below target. Berney is at the leading edge of our understanding of breeding waders, with much research being undertaken. Data-loggers placed into nests chart the time of day a predation event takes place. 92% of Lapwing and 71% of Redshank nest predations occur at night. This points to mammalian predators rather than avian.  Nest cameras on some nests take snaps as the predator strikes. The majority of snaps of Lapwing nest predations show Foxes as the predator. Perhaps contrary to general perception, most studies do not show crows as a major nest predator.

Once the nests hatch, chicks are a tasty snack for a wider variety of diners. At this stage, bird predators are a more significant predator and may include Marsh Harriers, Kestrels, Grey Herons or Buzzards. But predation is a highly complex issue, with a whole range of interacting factors. Habitat quality, weather, wetness and the abundance of prey (for both predator and prey) all play a part in the story.

Fox activity within a site has been shown to vary considerably between years. This may be related to the abundance of primary prey such as voles. Removal of Foxes is not always the answer, for example, it may allow mustellid predators to increase instead.
Many natural floodplain systems that have high numbers of breeding waders have cyclical patterns of productivity. They are good for waders some years, good for wildfowl, grebes and terns in others. Research on our reserves is instructive but understanding how these natural systems work is just as important. We cannot expect our nature reserves to deliver high wader productivity every year, but by managing the factors that are within our control, achieving some success in more years than not should be possible.

Tuesday, 24 August 2010

Eer mate, wanna Slow-worm?

Some things make your ecological blood boil. For example, having to fork out huge sums of money to relocate Water Voles from a wetland habitat creation scheme that will ultimately be better for Water Voles, and having to move said Voles to another new wetland that has to be fenced to prevent colonisation by the Water Voles that already frequent this Vole-filled landscape. What a waste of money. How much extra vole-filled wetland habitat could you have created with the money?
And then there’s reptiles. Where permitted development occurs, such protected animals are often moved out of harm’s way – translocated to new sites. Now imagine, could we get to the situation where ‘ecologists’ sidle up to reserve managers, touting bags of reptiles around as they slip gently to the ecological dark side. “Wanna Slow-worm for your reserve mate? How about an Adder or two?” Hmmm.
Now don’t get me wrong. Water Voles and reptiles deserve protection, and we must ensure that development takes account of protected species and habitats. But to end up spending huge sums of money looking after, and translocating, 100s if not 1000s of individual animals to unoccupied sites is surely not the best use of money. What percentage survive anyway?

Rather than waste excessive money on the individual animals surely it is more important to focus on the creation of new, good quality habitat, to provide a net gain for the species in the longer-term.

Thursday, 19 August 2010

Non-stop fishing (a two Ruff(e) trip).

Put together a nice reedy edge and a good population of Rudd to get a booming Bittern. Bittern photo by Andy Thompson.

Bitterns basically have simple requirements; tall, wet vegetation full of food. In the UK, this means reedbeds and fish. As the reedbed tour continues, this week we looked at fish populations and started at Titchwell. The reserve had one ‘boomer’ and one successful Bittern nest this year. Electro-fishing produced fair amounts of Rudd and Eels, both key prey for Bitterns, and the reedbed restoration some 5 years back has produced a good reed edge.

The freshmarsh at Titchwell is currently undergoing a make-over. Reed around the margins has been blitzed and islands have been re-profiled and re-levelled. Expect good birds over the coming years! Today the nearly dry marsh had plenty of waders around the diggers, but thankfully nothing rare: 200+ Dunlin, 100+ Golden Plover, plenty of Ruff, 10+ Whimbrel and a Garganey.

Strumpshaw Fen was the second stop of the tour. Despite the dry spring, Strumpshaw has surpassed itself this year with up to 4 boomers and 3 nests (usually only 1-2 boomers, with no nesting). The electro-fishing provided the answer: 2 years after a major saline inundation and fish kill, the fish population has rocketed. We caught 6 species at a biomass of 20+kg/ha of fish less than 300g (twice the estimated threshold for Bittern breeding). Personally, I was pleased with a fish ‘tick’ – Ruffe. We flushed a Bittern from the ditch with the highest fish density, Water Rails squealed, and the young Bearded Tits and Marsh Harriers everywhere pointed to a good breeding season. An Otter performing in front of the hide (a regular event this year) underlined the resurgence in fish populations.

And finally, a look around the reedbed at Otmoor. The catch here was mainly Pike and Perch, indicating an early stage in the development of the fish community. It will be a year or two yet before Bitterns boom here.  Two Little Stints, a Ruff, Hobby and 14+ Red Kites in the general area added to the interest.

Below: the freshmarsh at Titchwell takes shape.

Wednesday, 11 August 2010

Can a Corophium make a spooner randy?

Top: arriving at Havergate, Middle: Corophium volutator, Lower: a pair of smug post-breeding Spoonbills.

A break from ecological desk-work saw us discussing Spoonbills on Havergate Island. Havergate Island is one of my favourite sites, always with something to see. The island has hosted the largest UK gathering of Spoonbills for several years, with 15 present at the moment, down from the peak of 19 this year, but with up to 26 in recent years.

The recent news that Spoonbills have bred in Norfolk was a bit of a blow. Personally, I’m gutted. We have been trying for years to get them to breed on the island.

As in many species, when it comes to breeding, it appears that food is the key limiting resource. Spoonbills breed when their primary prey reaches abundance. Food intake is determined by the catch frequency and increasing prey weight increases the food intake rate but..... the average catch frequency decreases with prey size. With me so far?

A Spoonbill can sweep and catch up to 20 food items a minute, but at this rate the items will be small (such as the small crustacean Corophium), enough to keep a Spoonbill going but not enough to bring it into breeding condition. However, Sticklebacks ‘running’ from the sea into estuaries or lagoons in spring to breed are a different matter. Spring Sticklebacks have a high calorific value – they are nice and fatty. Catching one or two of these a minute is better for a Spoonbill than sweeping at full rate to catch 20 small food items. Sticklebacks migrating from the sea to breed are a key food item for returning Spoonbills in The Netherlands. Shrimps, especially Palaemonetes varians are also a favoured food item, but they only reach a reasonable size later in the season. The strategy at Havergate has been to try and maximise the primary food resource for the returning adults in April.
Oh well, perhaps next year.

Sunday, 8 August 2010


Top - the King George V Reservoir on a standard day, lower - the King George V Reservoir on a good day.

I rather like moulting Tufted Ducks. Perhaps it’s because there’s precious little else to look at on the rezzers at this time of year. Or perhaps it’s the challenge of pulling out something unusual amongst the scruffy legions as you scan through them one by one. Perhaps a Ring-necked Duck, or a Scaup, or even a Lesser. I’ve managed a Scaup or two and a couple of Fuggy Ducks over the years but that’s about it, as far as I can remember. Anyway it’s that time of year again, so my third count of the birds on the King George and Girling Reservoirs in the last fortnight turned up 925. The ‘unusuals’ were represented by 3 Goldeneye and the supporting cast by 24 Black-necked Grebes and a handful of Common Sandpipers.

In recent years, the August moulting flocks usually form the peak annual count of Tufted Duck in the Lee Valley, with an average peak of around 3,000 birds. The previous mid-winter peak now seems less pronounced. The moulting hordes on the reservoirs (including Walthamstow) make up over two-thirds of this total and are nearly all drakes. It appears that the drakes that arrive here to moult are from the eastern parts of the European range, principally Russia and eastern Scandinavia. Less than 10% of females undertake a moult migration. The sex ratio of 80%+ drakes is maintained on the reservoirs through the winter although the numbers drop, while the ratio on the gravel pits seems to be about 60% drakes. Do the deeper diving drakes prefer the deeper reservoirs? Do some of the moulting drakes stay for the winter or are they replaced by others? The moulting period is characterised by very stable flocks but they become highly mobile as the moult is completed. How much of the food resource have they depleted during this period? Is this why the Girling is crap during the winter? Something to ponder whilst checking for that Lesser.

Wednesday, 4 August 2010

When is a dry wetland good?

A return to the Ouse Valley this week, firstly looking at the now dry Berry Fen. Temporary wetlands of this nature generally become less productive for
birds over a number of years if they are kept wet, principally because food
resources decline. How often have you moaned about `scrapes' not attracting
birds any more? The aim is to have 2 or 3 highly productive flood years at Berry
Fen in every 5 years or so. These wet years will be good for breeding waders and
waterfowl, as well as passage waders, and hopefully the odd scarcity or two.
In the dry years, the site will be allowed to vegetate and be grazed. This will
replenish the seed resource, and the nutrients released on re-flooding the
vegetation will support abundant invertebrates. So Berry Fen will continue to
attract good birds - but not every year.

And then a look at progress on Ouse Fen. At around 500 hectares when completed, the Hanson-RSPB wetland project at Ouse Fen is set to become the UK's largest reedbed after gravel is extracted. However much of this needs to be imagined at the moment as only the early phases are in place. The photograph above shows the latest phase being landformed. The vehicle on the right is at the bottom of a channel through the future reedbed, the bulldozer is levelling out the base of the reedbed that will eventually be 70 cm under water.

Birds were thin on the ground today; 14 Little Egrets, a Garganey, a Ruff, 2 Hobby, 4 Turtle Doves and a handful of Teal were the highlights.