Biodiversity wildlife surveys
Wildlife survey data
Preliminary ecological surveys make an assessment of all the different habitats on a site, produce a list of all species encountered and comment on the suitability of habitats for species which may not have been seen during the visit. The results of these surveys, in conjunction with other survey information, help guide the conservation management of our sites.
Small mammalsFour sites in our southern area were surveyed for Dormice in 2004/2005. A sucessful breeding population of this Biodiversity Action Plan species was found around Hanningfield reservoir in Essex and so an ongoing population survey has been set up with results feeding into the National Dormouse Monitoring Programme.
Bat surveys have been carried out at a number of our sites to identify roosts and species that feed over the water. At the Trinity Broads, Norfolk, annual surveys of bats using the broads and our water treatment works have been carried out.
Data on the amphibian populations at our sites tends to be from incidental records that have been collated during the course of other survey work. Water bodies that contain large numbers of fish tend to have very small numbers of amphibians, the young of which are heavily predated by the fish.
Those of our sites, which have ponds and wetlands that do not hold fish are often inundated with adult frogs and toads during the breeding season. At Lound in Suffolk the warden at our site organises volunteers who help hundreds of toads make it safely across the road outside the site.
A great deal of amphibian work has been carried out at Broken Scar water treatment works in Darlington, where the entire amphibian population has been studied as part of a Great Crested Newt translocation programme. This scheme involved the creation of an entirely new habitat suitable for amphibians and the subsequent removal of the amphibian population from within the operational works to this site, over a three-year period.
WeBS is a national monthly survey that records numbers of each wetland bird species at sites where wildfowl and waders are know to congregate. This includes a number of our sites where dedicated volunteers collect data. This data is then collated by the Wildfowl and Wetlands Trust and depicted in graphical form to show population trends.
Breeding Bird Surveys and Bird Ringing
The British Trust for Ornithology (BTO) collates data from all the British teams of bird ringers. By using a standard method called ‘constant effort ringing’, bird ringing allows the origins and destinations of birds to be discovered and gives information on population dynamics and breeding success. Constant effort ringing has been carried out at Abberton reservoir since 1992.
A great deal of ringing work has been carried out on the black-headed gull colony at Grassholme reservoir in Teesdale and birds ringed at Stokesley sewage treatment works in North Yorkshire have been recorded as far away as Bloemfontain in South Africa.
Invertebrates
A variety of invertebrate surveys are carried out on our sites including, butterflies, moths, dragonflies, damselflies and bees.
Surveys have been commissioned at our northern area sites to identify the important areas for butterflies. The surveys look also at habitats and are timed to coincide with the flight times of the adult butterflies. The information enables us to ensure that sympathetic management practices, such as scrub control on grassland, are implemented and that appropriate monitoring schemes are put in place. The surveys also provide a snapshot in time of the status of the various species populations at the time of the survey. At Hanningfield, Essex, a local expert carries out a weekly survey of butterflies each summer.
Dragonfly and damselfly surveys were commissioned at our Northumberland reservoirs in 2002 and subsequent surveys have concentrated on operational sites with open water bodies, for example Chigwell in Essex.
The data highlighted the fact that reservoirs are not particularly suitable habitats for dragonflies and damselflies, due largely to the combination of water level draw down, lack of fringing emergent vegetation and large populations of fish, especially trout. Greater numbers and a wider variety of species are found at sites with adjacent ponds and wetlands, and those not managed as fisheries.
This information enables us to improve our sites through the creation of suitable habitats such as ponds, at locations where this is feasible.
Incidental records of moths are held for a number of our sites, collected during surveys for other wildlife or from one off moth surveys, for example Lound in Suffolk and Broken Scar, Darlington. At Broken Scar, mating lime hawk moths were found – one of the first records for this species in the north east for over a century. This large moth is known to be steadily moving its breeding range northwards.
Other sites have long-term, specific moth surveys set up. Scaling Dam is surveyed by dedicated groups and individuals who trap, identify and then release the moths. They have compiled a list of over 150 species for the site.
Botanical surveys using the expertise of local County Wildlife Trusts and with the support of English Nature have been carried out on all NWL northern area landholdings over 0.5 ha. The diversity found during these surveys is impressive. Derwent reservoir for example has over 230 vascular plant species, 156 species of fungi, 10 bryophytes (mosses and liverworts) and over 50 species of lichen.