WeBS Low Tide Counts AIMS METHODS Estuarine sites in the UK provide the most important habitat for non-breeding The scheme provides information on the waterbirds, acting as wintering grounds numbers of waterbirds feeding on for many migrants but also as stopover subdivisions of the inter-tidal habitat feeding locations for other waterbirds within estuaries. Given the extra work passing along the East Atlantic Flyway. that Low Tide Counts entail, often by the Core Counts on estuaries tend to same counters that carry out the Core quantify birds at high tide roosts. Counts, WeBS aims to cover most Although important, knowledge of roost individual estuaries about once every six sites provides only part of the picture, years, although on some sites more and does not elucidate the use that frequent counts are made. Co-ordinated waterbirds make of a site for feeding. counts of waterbirds are made by The WeBS Low Tide Counts scheme volunteers each month between has flourished since its inception in the November and February on pre- winter of 1992/93, with most of the established subdivisions of the inter-tidal major estuaries covered. The scheme habitat in the period two hours either aims principally to monitor, assess and side of low tide. regularly update information on the relative importance of inter-tidal feeding DATA PRESENTATION areas of UK estuaries for wintering Tabulated Statistics waterbirds, and thus complements the Tables 8 and 9 present three statistics information gathered by WeBS Core for 18 of the more numerous waterbird Counts. species present on 15 estuaries covered The data gathered contribute greatly during the 2009/10 winter: the peak to the conservation of waterbirds by number of a species over the whole site providing supporting information for the counted in any one month (with checks establishment and management of UK for count synchronicity made from Ramsar sites and Special Protection assessing proximity of count dates and Areas (SPAs), other site designations and consultation with Local Organisers); an whole estuary conservation plans. In estimate of the mean number present addition, WeBS Low Tide Counts enhance over the winter for the whole site our knowledge of the low water (obtained by summing the mean counts distribution of waterbirds and provide of each species for each count section) data that highlight regional variations in and the mean density over the site (in habitat use, whilst also informing birds per hectare), which is the mean protection of the important foraging number divided by the total area areas identified. WeBS Low Tide Counts surveyed (in hectares). The area value provide valuable information needed to used for these calculations is the sum of gauge the potential effects on the inter-tidal and non-tidal components waterbirds of a variety of human of each count section but omits the sub- activities which affect the extent or tidal areas ( i.e. those parts of the count value of inter-tidal habitats, such as section which are under water on a mean proposals for dock developments, low tide). recreational activities, tidal power barrages, marinas and housing schemes. Dot Density Maps Designing mitigation or compensation for WeBS Low Tide Count data are presented such activities can be assisted using as dot density maps, with subdivision of WeBS Low Tide data. Furthermore, the count sections into basic habitat effects on bird distributions of climate elements. The reason for such a change and sea level rise can be subdivision is to ensure species are assessed. 160 plotted on appropriate habitat areas and components proportionally and are to improve the accuracy of density then randomly placed within those estimates. Each section for which a areas. No information about the count has been made is divided into a distribution of birds at a finer scale maximum of three different habitat than the count sector level should be components: inferred from the dot density maps. For Inter-tidal: Areas that lie between mean all maps in the present report, one dot is high water and mean low equivalent to one bird, except where water. stated. The size of individual dots has no Sub-tidal: Areas that lie below mean relevance other than for clarity. low water. In more ‘open- As most estuaries have now been coast’-type situations, a sub- covered more than once at low tide, tidal zone reaching 500 m out density maps show the relative from the inter-tidal sections distributions of species in the winter of has been created arbitrarily, 2009/10 compared to an earlier winter. to indicate the approximate It is hoped that comparative dot density extent of visibility offshore distributions will lead to an easier and from land-based counts. fuller appreciation of low tide estuarine Non-tidal: Areas that lie above mean waterbird distribution, and changes high water (usually saltmarsh therein. The following colour although some grazing conventions apply to density maps: red marshes are also covered). dots = 2009/10 winter; blue dots = The mean count for the sector is then earlier winter; pale blue = water; yellow divided amongst a varying number of the = inter-tidal habitat (e.g. mudflat, different components, dependent on the sandflat); pale green = non-tidal habitat usual habitat preferences of the species (e.g. saltmarsh, reedbed); grey = not involved. For example, Dunlin dots are covered in one survey winter. More plotted exclusively on inter-tidal sections detailed information concerning analysis whereas Wigeon dots are spread across and presentation of WeBS Low Tide inter-tidal, sub-tidal and non-tidal areas Counts can be obtained from the Low (in proportion to the relative areas of Tide Counts National Organiser, or from these three components). the publication Estuarine Waterbirds at Currently, throughout all WeBS Low Low Tide (Musgrove et al. 2003) Tide Count analyses, mean low tide and mean high tide are taken from the most ESTUARY ACCOUNTS recent Ordnance Survey 1:25,000 maps WeBS Low Tide Counts were carried out (in Scotland, the lines on the OS maps at 15 different sites; estuary accounts are mean low water springs and mean for four of these are included here. To high water springs instead). It is allow space in this report for these sites recognised, unfortunately, that these which have not been counted for many maps represent the current real shape of years, dot density distribution maps for the mudflats, water channels and all other sites included in the 2009/10 saltmarshes to varying degrees of Low Tide Counts are available on our accuracy. However, in the interests of website at www.bto.org/webs/low-tide- uniformity across the UK, the Ordnance results or from the WeBS office. Other Survey outlines are adhered to counts, usually on limited numbers of throughout the analyses. sectors or only in one month, were made The maps display the average number in the winter of 2009/10 on Adur of birds in each count section as dots Estuary, Burry Inlet, Carmarthen Bay, spread randomly across habitat Firth of Forth, Loch Fleet and Ribble components of count sections, thus Estuary. These sites are not included in providing an indication of both numbers the estuary accounts, but data can be and density. It is important to note that obtained from the WeBS Low Tide Count individual dots do not represent the National Organiser upon request. precise position of individual birds; For the main site accounts, data were dots have been assigned to habitat collected during the period November to 161 February. Assessment of national and for selected species, which are those of international importance is based on national or international importance, or five-year peak mean counts from the are known to be undergoing site-level main species accounts in this volume of changes, where possible. General bird Waterbirds in the UK . Figure 64 shows distribution is described for the winter of the location of the sites discussed, and a 2009/10, focusing on species held in site description is presented for each important numbers at the site in estuary. Distribution maps are presented question. Figure 64. Map showing estuaries covered at low tide in the winter of 2009/10. 1: Loch Fleet; 2: Firth of Forth; 3: Breydon Water; 4: Orwell Estuary; 5: Stour Estuary; 6: Adur Estuary; 7: Langstone Harbour; 8: Medina Estuary; 9: Northwest Solent; 10: Portland Harbour & The Fleet; 11: Burry Inlet; 12: Carmarthen Bay; 13: Ribble Estuary; 14: Strangford Lough; 15: Belfast Lough. 162 Table 8. Sites covered by WeBS Low Tide Counts in 2009/10, with important bird numbers held. Numbers in parentheses refer to the location in Figure 64. For species codes see Table 7. International Importance National Importance Adur Estuary (6) None None Belfast Lough (15) BW SU, T., MA, SV, SP, E., GN, RM, RH, GG, CA, H., OC, RP, DN, CU, RK, TT Breydon Water (3) PG, WN, T., SV, AV, GP, BS, EW, DN, RU, RK L., BW, CN Burry Inlet (11) PT, OC, BW DB, SV, KN, DN, CU, GK Carmarthen Bay (12) CX, OC, SS GP, BW, GK Firth of Forth (2) PG, SU, BA, RK T., E., LN, CX, VS, GN, RM, GD, RH, RX, SZ, CA, OC, RP, KN, SS DN, RU, CU, TT Langstone Harbour (7) DB, DN, BW RM, GV, TT Loch Fleet (1) JI None Medina Estuary (8) None None Northwest Solent (9) DB, BW PT Orwell Estuary (4) BW DB, GA, PT, AV, KN, BW, RK Portland Harbour (10) MS DB, PO, RM, CO & The Fleet Ribble Estuary (13) WN, T., PT, OC, RP, GV, KN, SU, CA, AV, GP, L., RU, CU, CM SS, DN, BW, BA, RK, LB, HG, GB Stour Estuary (5) MS, BW, KN DB, SU, PT, AV, GV, DN, RK TT Strangford Lough (14) MS, WS, QN, SU, KN, BW, RK T., WN, GA, T., MA, PT, SV, SP, BW, RK E., GN, RM, BV, LG, GG, CA, CO, H., OC, RP, GP, GV, L., DN, BA, CU, GK, TT 163 Table 9 .