Scrapes and Bog Flush Dam Ponds on upland sites for breeding waders
Open water sources are valuable habitats on any farmland site, providing not only water points for all wildlife but importantly invertebrate breeding opportunities and therefore an increase in food supply for amphibians, mammals and birds. On upland sites as well as providing opportunity for amphibians and reptiles, they are particularly useful for breeding waders in the critical early and mid-summer periods for raising chicks. Wader chicks feed themselves so require damp ground to probe for insect larvae and worms. Steep sided sheugh’s may have water but are often inaccessible and do not provide a feeding area. With increasingly common dry periods in late spring in recent years, even in the uplands, the provision of small shallow depressions or pools can increase the chick survival rate. The soft tramped ground around the scrape is an ideal feeding area allowing young chicks to probe for grubs. Scrapes work well when they are set in a natural flush or to the side of a drain. Once installed, it is useful to return with a digger every other year to scrape the vegetation back for two metres from the shallow entry point.
CAFRE Hill Farm Centre manages a 70-hectare block at Vogie as a breeding wader site. Scrapes were installed in 2013 and along with annual rush cutting and appropriate grazing management these have contributed to a significant increase in breeding pairs of snipe on the site. Additional scrapes have been added to other areas of the hill farm over successive years.
Scrapes for waders can be as small as 2m x 2m across, with a depth of 25cms running to 50cms in the middle. The deeper part of the scrape increases the chances of retaining some water in very dry spells. If there are shallow open drains on the site, a scrape can also be pulled out by a digger from the side of the drain.
Bog Flush Dams as water sources for wildlife on blanket bog
Blanket bog habitat varies greatly between hills due to slope, aspect, the density of open drains and the presence or absence of underground peat pipes. Peatland is classified as blanket bog when the peat depth is over 50cms. Dry blanket bog moors are productive particularly for heather which can provide good cover, nesting and feeding habitat for Red Grouse, Meadow Pipits and Skylark. Large areas of tall heather are the preferred nesting habitat of Hen Harrier. The lack of open water on these dry moors, particularly at chick rearing stage is one of the main factors restricting these at risk species. Where the moor is dry due to a system of open drains then land managers should consider the methods of re-wetting. Where there are few open drains and only a few streams naturally occurring there is often a series of natural underground peat pipes which are moving significant volumes of water, eventually breaking to the surface in a small stream or commonly in a moss and rush flush lower down the slope. Walking uphill from a flush can provide an idea where to create a series of flush peat dams within the small natural valley. The more locations on the moor where there is some open water the less distance moorland birds have to bring chicks to feed and water, or indeed the less distance adults have to travel themselves. More sites also decreases the risk of being predated at the water source.
Creating Bog Flush Dams with borrow pit peat
Using a wide bucket a digger scrapes the scraw off from the small valley floor and sides and sets to the side. Swinging round the digger does the same with a borrow pit out to the side and up the hill. Buckets of sticky dark peat (unoxidised) are then taken from the borrow pit to create a dam at least 1 metre wide. The peat is packed down and into the sides, then the scraw is replaced onto the dam top. The scraw is also replaced in the bottom of the borrow pit which leaves a natural depression which will also act as a temporary water source. The borrow pit sides should be sloped by the bucket at the end of the process for the safety of quads or workers on foot. It is important to remember that the same volume of water has to ultimately leave the hill so the dams will fill up quickly and be allowed to overflow into the next one, preferably over the top of the whole level dam rather than at one point. Where the flush valley is narrow the dams can flow over the top into the next one, however where the water pressure is high in a wider point, an overflow pipe and splash stones maybe required at the receiving end to prolong the lifespan of the dam. A series of 8 bog flush dams which took approximately two to three hours to create successfully held water at the CAFRE Hill Farm, Creeve moor through the key dry spell at chick rearing time in 2021 from April to July.
Being aware of Land designations and Restrictions
If the land is designated such as within an SPA, ASSI or SAC then prior permission should be sought from NIEA, although these are minor works and have a biodiversity benefit. The works should be done between September and February to minimise any impact on ground nesting birds. Doing the works in the wetter period is also better to instantly see how the dams cope to allow modification and whether overflow pipes are required.