A Study of the Waterfowl Populations on Lough Carra, County^ Mayo, 1967-2006
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A Study of the Waterfowl Populations on Lough Carra, County^ Mayo, 1967-2006 •r' Christopher Meehan B.A. (Hons) in Heritage Studies This thesis was submitted in fulfilment of the requirements for the Master of Science degree by research at the Galway-Mayo Institute of Technology at Castlebar Supervisors: Dr. Sean Lysaght & Mr. John Tunney Head of School: Dr. Barbara Burns Submitted to the Higher Education and Training Awards Council, I hereby declare that this thesis is my own work Table of Contents Table of Contents ii List of Plates vi List of Figures vii List of Maps ix List of Tables x Acknowledgements xii Abstract xiv Chapter 1: Introduction 1.1 The Study Area 1 1.2 Previous Studies 4 13 The Study of Waterfowl on Lough Carra 1967-1980 7 1.4 Aims & Objectives 10 1.5 Literature Review 12 Chapter 2: Waterfowl Counting at Lough Carra & Methodology 2.1 A Brief History of Waterfowl Counting in Ireland 17 2.2 Waterfowl Counting at Lough Carra 1967-2006 19 2 3 Count Methodology, 1967-1980 22 2.4 Count Methodology, 1995-2004 25 2.5 Count Methodology for This Study, 2004-2006 27 Chapter 3: Waterfowl Populations on Lough Carra 1967-2006 3.1 The Waterfowl of Lough Carra 30 3.2 Results of Waterfowl Counting Programmes 1967-2006 32 3.2.1 Species Accounts: Mallard Anasplatyrhynchosp 33 Gadwall Anas strepera « 43 Shoveler Anas clypeata 51 Wigeon Anas penelope 59 Teal Anas crecca 67 Pochard Aythya ferina 75 Tufted Duck Aythya fuhgula 83 Goldeneye Bucephala clangula 91 ; Red-breasted Merganser Mergus serrator 99 Little Grebe Tachybaptus ruficollis 106 Great Crested Grebe Podiceps cristatus 110 Moorhen Gallinula chloropus 114 Coot Fuhca atra 117 Cormorant Phalacrocorax carbo 121 Mute Swan Cygnus olor 125 3.2.2 Scarce and Rare Species 129 Chapter 4: Count Calibration Experiments 4.1 Introduction to Count Calibration Experiments 133 4.2 Methodology for Count Calibration Experiments 133 4 3 Results of the Count Calibration Experiments 135 Chapter 5: Breeding Surveys & Population Estimates 5.1 Introduction to the Island Breeding Surveys 1968-1975 142 5.1.1 Methodology 1968-1975 142 5.1.2 Methodology 2005-2006 145 5.2 Interpreting Evidence of Nest Fate 148 5.2.1 The Identification of Nest Predators 150 53 Results of Island Breeding Surveys 2005 & 2006 152 5.4 Dog Search/Foot Search Experiment 174 5.4.1 Methodology 174 5.4.2 Results 175 5.4.3 Discussion 176 5.5 Mallard Clutch Sizes 179 5.6 Nest Initiation Dates for Mallard on Lough Carra 183 5.6.1 Re-nesting 186 5.7 Potential Predators of Waterfowl Nests at Lough Carra 190 in 5.7.1 Amen can Mink Mustela vison 191 5.7.2 Hooded Crow Corvus corone cornix 195 5.7.3 Other Potential Predators 196 5.8 All Breeding Waterfowl Species on Lough Carra 201 5.8.1 Breeding Species Accounts 203 5.8.2 Site Accounts 233 5.8.3 Geographical Spread 239 Chapter 6: Habitat Analysis 6.1 Introduction 240 6.2 Reedbed Analysis 240 6.2.1 Reedbeds & Waterfowl 241 6.2.2 The Study of Reedbed Density & Distribution on Lough Carra 243 6.2.3 Comparative Analysis 246 63 Island Habitat Analysis 250 6.3.1 Doonbeg Island - A Comparative Analysis 252 63.2 Methodology 253 63.3 Findings 254 6.3.4 Stronach’s Island Habitat Experiment 261 6.4 Possible Habitat Changes m the Lough Carra Sub-Catchments 263 6.4.1 Methodology 265 6.4.2 Habitat Changes in the Sub-Catchments - A Post Drainage Analysis 269 6.4.3 Land Use Changes m the Carra Sub-Catchments 277 Chapter 7: Discussion 7.1 Waterfowl Countmg Schemes, Counting at Lough Carra & Methodology 282 7.2 The Trends of Nine Species of Waterfowl at Lough Carra from 1967-2006 & Comparisons to Trends m Irish, British and European Populations 286 7.2.1 General Discussion of Trends in Six Waterfowl Species at Lough Carra from 1995-2006 318 7.3 Reedbed Analysis 321 7.4 Drainage & Land Conversion 323 7.5 Island Habitat Changes 325 IV 7.6 Predation & Predators of Waterfowl & their Nests on Lough Carra 330 7.7 Summary of Decline Hypotheses & Possible Fluctuation Factors for Individual Species 338 7.8 Lough Carra Designations & Management 341 Chapter 8: Conclusions 344 Appendices 348 Bibliography 351 v List of Plates Plate 1: Mallard 33 Plate 2: Gadwall 43 Plate 3: Shoveler 51 Plate 4: Wigeon 59 Plate 5: Teal 67 Plate 6: Pochard 75 Plate 7: Tufted Duck 83 Plate 8: Goldeneye 91 Plate 9: Red-breasted Merganser 99 Plate 10: Great Crested Grebe 113 Plate 11: Nest Hog Island C 05 171 Plate 12: Nest Bush Island A 05 171 Plate 13: Nest Horse Island A 05 171 Plate 14: Cane Nest Marker 171 Plate 15: Egg Membrane from hatched egg 171 Plate 16: Hatched egg 171 Plate 17 & 18: Eggshells after predation by an avian predator 172 Plate 19 & 20: Eggshells after predation by a mammalian predator 172 Plate 21 & 22: A nest before and after predation 172 Plate 23: A mink trail through the Sesleria zone 194 Plate 24: A Mallard wing after mink predation 194 Plate 25: Little Grebe 223 Plate 26: Coot on nest 227 Plate 27: Reedbed at Lough Carra 246 Plate 28 & 29: Hog Island showing heavily wooded habitat and Ivy 259 Plate 30: Bush Island showing trackway of mixed grasses 259 Plate 31: Bush Island showing heavily wooded area 259 Plate 32: The beginning of Ecological Succession on a small rocky zone 259 Plate 33: Horse Island 259 Plate 34&35: Doonbeg Is: Area 2 and Area 3 260 Plate 36&37: Doonbeg Is: Open Schoenus and Sesleria Zones 260 Plate 38&39: Doonbeg Island: From the cast and area of new growth 260 vi List of Figures Figure 1: The Number of waterfowl counts conducted at Lough Carra 1967-2006 21 Figure 2: Mallard Annual and Monthly Fluctuation Charts A-M 34 Figure 3: Gadwall annual and monthly fluctuation charts A-J 44 Figure 4: Shoveler annual and monthly fluctuation charts A-K 52 Figure 5: Wigeon annual and monthly fluctuation charts A-J 60 Figure 6: Teal annual and monthly fluctuation charts A-K 68 Figure 7: Pochard annual and monthly fluctuation charts A-K 76 Figure 8: Tufted Duck annual and monthly fluctuation charts A-K 84 Figure 9: Goldeneye annual and monthly fluctuation charts A-K 92 Figure 10: Red-breasted Merganser annual and monthly fluctuation charts A-H 100 Figure 11: Little Grebe annual and monthly fluctuation charts A-F 106 Figure 12: Great Crested Grebe annual and monthly fluctuation charts A-E 110 Figure 13: Moorhen annual and monthly fluctuation charts A-D 114 Figure 14: Coot annual and monthly fluctuation charts A-F 117 Figure 15: Cormorant annual and monthly fluctuation charts A-F 121 Figure 16: Mute Swan annual and monthly fluctuation charts A-F 125 Figure 17: The Land & Boat totals for 15 waterfowl species 139 Figure 18: Percentage of successful, predated and deserted nests 173 Figure 19: The decline in the clutch sizes of Mallard at Lough Carra 182 Figure 20: Initiation periods for 15 Mallard nests, 2005 & 2006 189 Figure 21: Initiation periods for 1,050 Mallard nests, 1968-1973 189 Figure 22: Breeding Season peak monthly counts of Mallard, 2005/06 207 Figure 23: Breeding Season peak monthly counts of Mallard, 1971/73 207 Figure 24: Breeding Season peak monthly counts of Tufted Duck, 2005/06 212 Figure 25: Breeding Season peak monthly counts of Tufted Duck, 1970/71 212 Figure 26: Breedmg Season peak monthly counts of Red-b Merg, 2005/06 216 Figure 27: Breedmg Season peak monthly counts of Red-b Merg, 1968/69 216 Figure 28: Breeding Season peak monthly counts of Gr Cr Grebe, 2005/06 220 Figure 29: Breeding Season peak monthly counts of Little Grebe, 2005/06 223 Figure 30: Breeding Season peak monthly counts of Moorhen, 2005/06 225 vn Figure 31: Breeding Season peak monthly counts of Coot, 2005/06 227 Figure 32: Breedmg Season peak monthly counts of Mute Swan, 2005/06 229 Figure 33: Breedmg Season peak monthly counts of Gadwall, 2005/06 232 Figure 34: The number of different species recorded at 12 sites at L Carra 238 Figure 35: The mean number of nine waterfowl species present m the northwest & southeast basms of Lough Carra from the start of March to the end of July 2005 & 2006 239 Figure 36: Lockhart’s counts of six duck species from six wetland sites, 1981 274 Figure 37: Meehan’s counts of five duck species from six wetland sites, 2005 274 Figure 38: The January/September Peaks of Mallard on Lough Carra 1968/74 288 Figure 39: The January/September Peaks of Mallard on Lough Carra 2000/06 288 Figure 40: The growth rate m Tufted Duck populations over four western lakes from the Wmter Wetlands Survey, 1984/85-1986/87 to the Irish Wetland Bird Survey 1994/95-2000/01 311 Figure 41: The mean annual peaks of nine waterfowl species on Lough Carra from 1967-1980 and 1995-2006 317 Figure 42: The percentage of Mallard nests found in available habitat types 329 Figure 43: The percentage of successful, predated and deserted nests m relation to habitat type from 15 Mallard nests 329 Figure 44: The percentage of Mallard nests predated by different predator species, 2005-2006 337 vm List of Maps (Includes Aerial Photographs) Map 1: Map showing location of region and the western lakes 2 Map 2: Lough Carra with main areas and numbered islands 9 Map 3: Stronach’s waterfowl census line transects, 1967-1980 23 Map 4: Aerial photograph of Lough Carra with the 27 Count Points from which waterfowl were counted, 1995-2006 28 Map 5: The ten islands on Lough Carra surveyed for breeding waterfowl in 2005-2006 143 Map 6: The distribution of the Common Reed on Lough Carra after Huxley (2003) 244 Map 7: The distribution of the Common Reed on Lough Carra after Schackleton (1975) 245 Map 8: The main changes in the distribution and extent of the Common Reed on Lough Carra from Huxley after Schackleton 247 Map 9: Aerial photograph of Doonbeg Island, Illanatrim & Bush Island 253 Map 10: Sketch map illustrating the extent and distribution of vegetation on Doonbeg Island, 2006 257 Map 11: The extent and distribution of vegetation on Doonbeg Island c.