Understanding declines in the population size of migratory birds Thomas Oliver Mondain-Monval This dissertation is submitted for the degree of Doctor of Philosophy November 2020 Lancaster Environment Centre Declaration I declare that the work in this thesis is my own and has not been submitted elsewhere for the award of any other degree. 1 Table of contents Declaration ................................................................................................................................. 2 Table of contents ....................................................................................................................... 2 Acknowledgements .................................................................................................................... 6 Abstract ...................................................................................................................................... 7 List of figures .............................................................................................................................. 8 List of tables ............................................................................................................................. 11 Chapter 1 Introduction ............................................................................................................ 13 Reasons for declines in migratory birds ............................................................................... 13 Climate change and phenology ........................................................................................ 13 Pressures during breeding ............................................................................................... 14 Pressures during migration .............................................................................................. 15 Pressures on the wintering grounds ................................................................................ 16 Migration theory .................................................................................................................. 17 Winter .............................................................................................................................. 17 Migration routes and connectivity ................................................................................... 19 Staging and stopover sites ............................................................................................... 20 Carry-over effects............................................................................................................. 21 Macroecological patterns ................................................................................................ 22 Tracking individuals using light-level geolocators............................................................ 23 Study species: the common sandpiper ................................................................................ 25 Breeding ecology .............................................................................................................. 27 Migration routes, phenology and stopover sites ............................................................. 29 Wintering ecology ............................................................................................................ 32 Aims...................................................................................................................................... 33 Chapter 2 Factors affecting breeding success in the common sandpiper and the potential impact of disturbance .............................................................................................................. 34 Introduction ......................................................................................................................... 34 Methods ............................................................................................................................... 37 Study population and nest monitoring ............................................................................ 37 Estimating hatching date ................................................................................................. 39 Calculating first egg date for failed nests ......................................................................... 40 Flight initiation distance ................................................................................................... 43 2 Downloading public rights of way and road maps ........................................................... 43 Rainfall data ..................................................................................................................... 44 Statistical analyses ........................................................................................................... 44 Results .................................................................................................................................. 47 Hatching success .............................................................................................................. 47 Humans approaching the nest ......................................................................................... 51 Fledging success ............................................................................................................... 53 Discussion ............................................................................................................................. 56 Chapter 3 The ecology and behaviour of common sandpipers in winter ................................ 61 Introduction ......................................................................................................................... 61 Methods ............................................................................................................................... 63 Ringing, return rates and sexes ........................................................................................ 63 Molecular sexing .............................................................................................................. 64 Stable Isotopes ................................................................................................................. 65 Habitat choice .................................................................................................................. 66 Foraging success............................................................................................................... 67 Response to conspecifics in winter .................................................................................. 68 Results .................................................................................................................................. 70 Ringing, return rates and sexes ........................................................................................ 70 Large scale wintering distributions .................................................................................. 71 Habitat choice and foraging success ................................................................................ 73 Response to conspecifics in winter .................................................................................. 78 Discussion ............................................................................................................................. 82 Return rates ..................................................................................................................... 82 Wintering segregation of common sandpipers ............................................................... 82 Habitat choice and foraging success ................................................................................ 83 Response to conspecifics ................................................................................................. 85 Conclusion ........................................................................................................................ 86 Chapter 4 The effects of geolocators on return rates, condition and breeding success in common sandpipers................................................................................................................. 87 Introduction ......................................................................................................................... 87 Methods ............................................................................................................................... 88 Catching birds and fitting geolocators ............................................................................. 88 3 Analyses ........................................................................................................................... 90 Results .................................................................................................................................. 92 Other effects .................................................................................................................... 95 Discussion ............................................................................................................................. 95 Chapter 5 Migration routes, connectivity and wind assistance in the common sandpiper .... 98 Introduction ......................................................................................................................... 98 Methods ............................................................................................................................