1.      The key waterbirds mostly have distinct feeding strategies and preferred food type.  Large numbers of waders exploit the rich feeding grounds of the River Steeping estuary at Gibraltar Point.  The mudflats provide dense populations of invertebrates including mollusca, crustacea, polychaetes, nematodes etc.  Extensive studies have been carried out in the Wash (Goss Custard, ITE etc) to monitor the density and distribution of prey for the key waders in the varied substrates.  Eastern Sea Fisheries carry out additional monitoring of commercial species and in recent years a strong correlation has been determined between a crash in the Wash wintering oystercatcher numbers with minimal recruitment by the cockle population.  Of the important wildfowl, shelduck seek out small molluscs (Hydrobia) on the flats and saltmarshes and the brent geese graze marine algae on the flats, saltmarsh grasses or grasses and crops on adjacent arable or pasture.  It is imperative that measures are in place to safeguard the habitats which are used by these populations and monitor the condition of these habitats and their use by key waterbird populations.  Recent low numbers for some species have indicated problems with food supply and triggered research and management measures ie oystercatchers and cockles.

2.  Flocks of feeding and roosting waterbirds are not tolerant of disturbance and may fail to return to a site which offers optimum habitat if disturbance is repeated.  Disturbance may occur through natural factors, such as birds of prey or through a range of human activities. Disturbance becomes more critical if birds are already stressed, for example during periods of hard weather. Furthermore, disturbance at roost may be of greater concern due to the limited number of safe roost refugia and the flight distances between them.  Following disturbance, species such as knot and bar-tailed godwit may remain airborne for considerable lengths of time, thus expending valuable energy.  Various waders may use roost sites for differing lengths of time.  Sanderling and ringed plover are usually the first species to arrive and settle at the roost site.  Conversely, oystercatcher and bar-   tailed godwit are the last to arrive.  Oystercatcher is the last species to leave the roost.  Grey plover appears to be the most sensitive species to disturbance and exhibits a high roost fidelity, whilst bar-tailed godwit tends to seek out roost sites where there is a wide area of all- round visibility.

3.  Waterbirds are particularly affected by prolonged periods of freezing conditions.  During such periods, some birds may attempt to leave in search of alternative feeding grounds further south or west.  However, the majority may show a high level of site fidelity when on the wintering grounds.  Some of the short- billed waders, may have difficulty in detecting prey items where the intertidal mud is frozen.  Conversely, upper marsh species like redshank will suffer as these areas are worst hit during freeze conditions.

4.  The activity patterns of these birds is entirely governed by the tidal cycles.  Thus, night- feeding is often necessary to exploit periods of low tide.  Wader feeding patterns have been linked to substrate and prey type through low-tide counts.

5.  Intertidal mudflats and sandflats provide the feeding grounds for the principle waders of importance.  The substrate type and consequent populations of invertebrates governs the suitability of different zones for different species.

6.  During high tides, the shingle ridges draw vast flocks of waders to roost.  The juxtaposition of feeding grounds and roost is important for energy saving, particularly during periods of hard weather.  There are two key roost sites on the NNR, which provide a safe refuge for waders at high tide.  Although the geomorphology changes, invariably large shingle ridges occur without vegetation and with clear all round visibility providing suitable roost sites.  The outer bar (compt 1/11/E) comprised the primary roost although the build up of embryo dunes at its base have rendered that area unfavourable.  Thus the newly formed Millennium Ridge (compt 1/11/F) has become important.  On the highest tides or following disturbance at the primary roost, birds may then move further north to compt 1/15 where the extensive open shingle on Greenshanks Ridge provides a secondary retreat.  Roost sites may host an assemblage of different species, although use of roosts may vary in different species.

7.  Saltmarsh provides favoured feeding grounds for brent geese and to a lesser extent, shelduck.  On the neap tides, waders may roost along the saltmarsh margins, but on the spring tides (6.8 m and above) the shingle ridges provide the only suitable roost sites.  On the highest tides, redshank and curlew do not tend to assemble at roost on shingle bars with the other species.  Both tend to remain in upper saltmarsh, although curlew may move inland and return to the estuary in the evening.  Redshank have occasionally used the Fenland Lagoon (compt 1/6) as an autumn roost which has involved up to 1000 birds.

8.  Wader and wildfowl population dynamics will be affected by factors experienced on migration or on the breeding grounds; therefore targets may be influenced by elements far beyond our influence or knowledge.