Digging up emeralds

Ditching work at Holkham's marshes

Anyone glancing over the marshes at Holkham in September and October is bound to have seen a large yellow tracked digger. Many people stop and ask what sort of work is it doing? The simple answer is that it is dredging the ditch systems, yet really the answer is a lot more involved than just simply doing a bit of dredging work.  Together with a series of sluices the ditches help us manage the water levels. For the ditches to do their job a certain amount of maintenance has to be done regularly and this means dredging out silty mud that accumulates and impedes the water flow.  As you can imagine the wildlife of the dykes is varied and often prolific. For that reason we try to work on a seven year rotation so that there is plenty of time for the flora and fauna to re-establish.

The Grey Herons of the marsh become most confiding during ditching work ever on the lookout for fish and eels.

Whilst we do not actually drive the machines ourselves we are often at hand assisting the driver in clearing up rubbish that has been ‘slubbed’ out or helping replace culverts and gateways.  It can be messy work but the amount of wildlife seen can be quite astounding. The dykes of Holkham are an incredibly important part of our ecosystem and a great indicator of their health is the presence of Eels. They are always encouraging to see and form an essential part of the menu of birds such as Bitterns and Grey Herons. It is quite normal to see two or three Grey Herons or even the odd Little Egret wandering about on the ‘slubbings’ metres  away from the digger looking for rich pickings. A good number of fish are also present, Roach in particular. We are quite unaware at just how many we have, but suffice to say there must be plenty judging from the concentrations we occasionally see and the constant fishing activities witnessed by our newest residents, the Great White Egrets. They are constantly pacing back and forth through the shallows of the dykes these days in search of fish to eat.

The Willow Emerald Damselfly, a new species for the reserve

As I was helping out one day this year a flash of green caught my eye on some waterside reed. It was a small elongated yet dainty damselfly. A closer inspection revealed it to be a Willow Emerald and a new species for the reserve. This southern European species first colonised the Suffolk coast in 2009 and has been slowly pushing north ever since. This year has seen more than normal numbers appear along the coast of north Norfolk and it had been a species we were expecting to find at some stage. It prefers dykes that have overhanging willows where it lays its eggs under the bark. With some of our dykes having willows in sunny situations it really does look like we perhaps have the perfect habitat for a future flourishing population.

A fearsome looking Water Scorpion

Another interesting insect seen was a Water Scorpion. This rather fierce looking insect (unrelated to a true scorpion) has a long ‘sting’ like protuberance at its rear end yet this is actually a respiratory tube that it holds above the water thus allowing it to breath underwater. Instead of having claws on its front legs like a Scorpion it actually has scythe-like front legs that are still used in a similar fashion to catch its prey.

Water Shrew, a rarely seen inhabitant of the reserve's dykes

For me however the most exciting find of the year was a Water Shrew. Having been a keen naturalist for 36 years it was a species that I should have seen before but it had always eluded me. It is also said to be a relatively common well distributed species across the British Isles yet one that is pretty much solely aquatic and that was my excuse for not having seen one. There have been one or two sightings through the years on the reserve, yet never by me so when I saw a very dark almost black shrew, I knew my luck was about to change. It proved to be a very worthwhile learning experience. Water Shrews have Mole-like black fur above and most have contrasting white underparts; this one however was more dusky coloured below making it not so easy to identify. Certain features could be seen that eliminated the more widespread Common Shrew such as its larger size, its pale tipped ears and its hairy feet, toes and tail which have evolved to enable it to swim through the water with ease. It could well be a common species on the reserve or it could be a rarity, something we currently cannot answer.

The fresh foot prints of an Otter

Another mammal that continues to elude me on the reserve is the Otter. A regular recently told me when he was young in the early 1950s he used to ‘bunk off’ school especially to watch a family of Otters sliding into one of the ditches on the marsh. Following the species nationwide demise due to the use of organo-chloride pesticides running off into river systems it took until after the new millennium for Otters to return to Holkham. Since 2012 we know through finding foot prints that the species is now present again, but being mostly nocturnal it remains very difficult to see. I think I must now be the only member of staff who works on the reserve who has yet to see an Otter here, but I’m sure that time will come soon. Another reason they are so difficult to see is the sheer distance they travel. Between Wells and Burnham Norton the reserve’s three main areas of grazing marshes are an intricate wetland of cattle grazed fields that are all bordered and inter connected by a series of fresh water dykes and ‘drains’. This again brings us back to the management of the reserve and the reasons for dyke dredging. The basic system works like this; water accumulates, be it rain water or from in-field springs and drains into the dykes which then ultimately flow out through the fields to the sea. Some are old ‘foot’ drains used from the 1700s onwards when the fields (formerly brackish and salt marshes) were drained so that the arable crops could be grown. We are able to control this flow due to a series of dams and sluices that allows us to either hold back and retain water (giving us wetter fields) or release it (thus drying areas out).

Andy Bloomfield

Warden

The splendour of Little Egrets

 

Little Egret feeding in Wells Harbour

One of our most recent pieces of survey work on the reserve was to assist in a coast wide count of Little Egrets at their overnight roosts sites. These small white herons with gleaming yellow feet are now a common sight along the north Norfolk coast, particularly on the salt marshes. Here they can be seen in shallow pools or creeks, ever on the lookout for small fish or crustaceans to eat. This was certainly not always the case, they were once exceptionally rare.

Standing at dawn on a cool late September morning when the first white shapes (of a final total of 81) started to break cover and head off from the safety off their night time woodland residence and illuminated by the rising rays of sunlight, all my thoughts raced back to my first ever encounter with a Little Egret. Wells school in the 1980s boasted a thriving bird club and periodically trips would be undertaken to the various reserves along the coast. Strangely my first ever trip out with the club was along the coast to Cley and Salthouse to see Avocets and Black-tailed Godwits in 1981 yet the most exciting species we encountered was a Little Egret. This was big news at the time as a gathering of twitchers lined the coast road with all their telescopes and binoculars pointing north into the fields at a vivid eye catching white shape. Huddled into the reeds at a great distance it was hardly the most inspiring of sightings, yet it certainly captured my young imagination that all these people had actually arrived there from all corners of the country to see what essentially looked like a  white bundle of feathers. How times have changed, nowadays most birders (and certainly not twitchers) don’t even give these birds a second glance. So what happened in the intervening years?

Little Egrets flying to roost

In the 1980s growing numbers of Little Egrets progressed north up the coast of France from a stronghold in more southerly, warmer wetlands. A combination of milder winters, good breeding seasons and an abundance of habitats combined with greater protection allowed the species to breed in good numbers right up to the coast of Brittany. From here greater and greater numbers began to cross the English Channel and finally after several years of a growing wintering population the first breeding pair colonised Brownsea Island off the Dorset coast in 1996. Ever increasing numbers spread out across the British Isles and by 2009 over 800 pairs were found to be nesting and a far cry from the not too distant past.

Little Egrets prefer the vast north Norfolk salt marsh system for feeding

Holkham NNR actually became very much an integral part in the Norfolk story. Despite not recording its first until 1988, it actually became the first place to have a wintering pair (on the NNR’s saltmarshes at Warham/Stiffkey) and then the first breeding birds in 2002 (in a wet woodland site within the grazing marshes). From the first five pairs in 2002 their increase was swift; by 2004 up to 42 pairs nested, making it the county’s premier site for the species. Thanks to global warming we gained a new resident species that had barely been given a thought of being a potential colonist until changing times in the 1980s. Its sudden appearance and colonisation almost matches that of the Collared Dove a couple of decades before.

Shrimps are one of the main sources of food.

Little Egrets can be seen these days in any spots where there is marshy ground and suitable prey can be found although the saltmarshes and harbours still attract the lion’s share. Here the tidal rhythms ensure that there is a plentiful food supply of crabs, shrimps and fish. Take time to sit and watch an egret feeding and you will be enthralled at their various methods. Sometimes a bird might be standing rigidly still, head cocked to one side waiting for a movement below whilst another favoured technique is foot shuffling. Then the bird moves very slowly with seemingly only its feet quivering under the water to stir up the mud and water and provoke movement of any potential prey. Another method sometimes seen is the half wing cocked position when its wings are held partially aloft and spread out, thus creating shade below. This may be as much to enable the bird to see well as for fish to enter under a calmer place thus leaving them vulnerable for a fatal strike from the egret’s sharp bill. Egrets are usually solitary feeders but occasionally larger congregations may be seen when a feeding frenzy erupts with birds chasing in every direction amidst a shoal of fish.

Part of the courtship rituals during the breeding season

Always seemingly immaculate, Little Egrets take on an even more beautiful new identity in the spring and summer when they are breeding. Elaborate plumes grow on their crown and fine lace-like feathers grow on their backs. These form part of highly involved social displays and to witness such a sight instantly leaves the impression that one of the finest rituals of any European bird has been witnessed.

Andy Bloomfield

Warden