The Conservation Ecology of the European Nightjar (Caprimulgus Europaeus) in a Complex Heathland-Plantation Landscape
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The conservation ecology of the European nightjar (Caprimulgus europaeus) in a complex heathland-plantation landscape. Katrina Sharps A thesis submitted for the degree of Doctor of Philosophy at the School of Environmental Sciences, University of East Anglia, Norwich, UK. May 2013 © This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with the author and that use of any information derived there from must be in accordance with current UK Copyright Law. In addition, any quotation or extract must include full attribution. Acknowledgements Firstly, I would like to thank my primary supervisor Paul Dolman for his constant advice, support and enthusiasm throughout this PhD. I am also grateful to the other members of my supervisory team: Ian Henderson of the British Trust for Ornithology (BTO) and Andrew Lovett of UEA, for their useful guidance. Special thanks also go to Neal Armour-Chelu of the Forestry Commission and Greg Conway of the BTO for practical advice for the fieldwork and their invaluable experience and knowledge of forest management and working with nightjars respectively. Next, I would like to thank the other members of my radio-tracking and moth trapping teams – Vivien Hartwell, Laura Wilkinson, Elwyn Sharps, Alastair Feather, Kirsten Miller and Isobel Winney. Their efforts were tireless and they showed dedication to the project throughout. Additional thanks to all radio-tracking and nest finding volunteers, including Forestry Commission, RSPB and Wildlife Trust staff. Nightjars were caught and tagged by BTO staff, including Ian Henderson and Greg Conway. Nightjar faecal pellets were dissected by Alastair Feather. Advice on beetle fragments in samples was provided by Martin Collier, Darren Mann, Eileen Reilly and Nicki Whitehouse. Nightjar nest camera data were collected by Greg Conway, Chas Holt, Mark Hulme, Simon Pickett, Sabine Schäfer and Kerry Skelhorn, supervised by Paul Dolman and Ian Henderson. Nightjar nest camera data were extracted from MemoCam events by Lucy Wilshaw. Advice on home range kernels was provided by Art Rodgers and statistical procedures by Ben Bolker. GIS habitat layers were provided by Forestry Commission, Norfolk Wildlife Trust, Suffolk County Council and the Centre for Ecology and Hydrology. This PhD was funded by a UEA Dean’s Studentship. Additional financial support for the project was provided by the Sita Landfill Trust, the BTO, the Forestry Commission, Natural England and the Pamela Salter Trust. 2 Abstract The conservation ecology of the European nightjar (Caprimulgus europaeus) was investigated in a complex heathland-plantation landscape in eastern England. Using radio telemetry, 31 nightjars were tracked in 2009 and 2010. The breeding behaviour of males was found to have potential implications for nightjar survey methods. While surveyors should be aware of the possibility of song territory overlap between male birds, results suggest that the occurrence of roaming unpaired males would not lead to an over-estimate in population. Home range 95% kernels for females, paired and unpaired males were an order of magnitude larger than song territories, highlighting the importance of foraging habitat in the broader landscape. Compositional analysis showed that foraging nightjars selected open canopy plantation forest (aged 5-10 years) and newly planted coupes (aged 0-4 years), with grazed grass-heath also used when available within 2km of the territory centre. Open ungrazed and un-planted habitat within the forest was avoided by birds, relative to availability. Moth trapping indicated that birds may choose foraging habitat based on the ease of prey capture rather than prey abundance. Dissection of nightjar faecal pellets demonstrated that moths and beetles were key components of the diet and that variation in diet during the breeding season may be due to changes in resource abundance and varying chick requirements. Comparison of the diets of birds nesting or roosting at varying distances from grass-heath suggested that forest and heathland habitats provide similar foraging resources for the nightjar. Behavioural data from nest camera footage indicated that the factors influencing the duration and frequency of adult non-attendance at the nest were incubation stage, temperature and chick requirements. This thesis combines investigations of nightjar breeding behaviour, home range, habitat use and diet, which can be used as an evidence base to inform conservation management. 3 Table of contents Chapter 1 Introduction The importance of applied ecology for conservation management ................................. 11 Integrating biodiversity into forest management .............................................................. 12 The nightjars (Family Caprimulgidae, sub-family Caprimulginae) ..................................... 14 Thesis outline ..................................................................................................................... 15 Aims .................................................................................................................................... 15 Chapter outline .................................................................................................................. 16 References ......................................................................................................................... 18 Chapter 2 General methodology Nightjar fieldwork .............................................................................................................. 23 Investigating habitat use .................................................................................................... 23 Radio telemetry methodology ........................................................................................... 24 Home range analysis techniques ....................................................................................... 29 Compositional analysis ....................................................................................................... 30 Dietary analysis .................................................................................................................. 31 Behaviour at the nest ......................................................................................................... 32 References ......................................................................................................................... 34 Chapter 3 Song territory overlap and size variation among breeders and non-breeders: implications for censusing nightjars Abstract .............................................................................................................................. 39 Introduction ....................................................................................................................... 39 Methods ............................................................................................................................. 41 Study site ....................................................................................................................... 41 Nightjar radio-telemetry ................................................................................................ 42 Nightjar breeding status ................................................................................................ 42 Nightjar song territories ................................................................................................. 42 Results ................................................................................................................................ 44 Song territory overlap .................................................................................................... 44 4 Song territory size .......................................................................................................... 44 Discussion ........................................................................................................................... 45 References ......................................................................................................................... 49 Chapter 4 Home range and habitat selection of the European nightjar (Caprimulgus europaeus) in a heathland-plantation landscape Abstract .............................................................................................................................. 52 Introduction ....................................................................................................................... 52 Methods ............................................................................................................................. 54 Study site ....................................................................................................................... 54 Radio-telemetry ............................................................................................................. 55 Breeding status .............................................................................................................. 55 Nightjar ranging behaviour ............................................................................................ 56 Compositional analysis .................................................................................................. 57 Moth trapping ................................................................................................................ 58 Temperature measurements