Gary Clewley

Senior Research Ecologist

Gary’s role as a Senior Research Ecologist includes leading fieldwork, analysis and reporting on a variety of relevant projects within the Wetland and Marine Team.

Interests & Responsibilities

Gary has worked on a range of projects within the BTO, both in terrestrial and marine environments, and has particular strengths in field ornithology and spatial analysis. He is an experienced bird ringer and trainer and has used a wide variety of novel tracking techniques, particularly with gulls, waders and wildfowl. 
His main interest in applied ecology include using high quality evidence for decision making in wildlife management, especially where potential conflicts may occur such as the construction of renewable energy developments or collision risks in the aviation industry. Other interests include the assessment and management of invasive non-native species and their interaction with native species and habitats.


PhD Ecology, Imperial College London - ‘Post-release assessment of Aphalara itadori (Hemiptera: Psyllidae) as a classical biological control agent of Fallopia japonica (Polygonaceae)’ – 2011- 2015 
MRes Entomology, Imperial College London - 2010 
BSc Zoology, University of Reading - 2009

Recent BTO Publications

Clewley, G.D., Thaxter, C., Scragg, E.S., Masden, E.A., Barber, L.J., Conway, G., Clark, N.A. & Burton, N.H.K. 2023. Daily, seasonal and annual variation in area use of Lesser Black-backed Gulls (Larus fuscus) related to offshore renewable developments. Bird Study View at journal website (DOI: 10.1080/00063657.2023.2190080)
Pearce-Higgins, J.W., Humphreys, E.M., Burton, N.H.K., Atkinson, P.W., Pollock, C., Clewley, G.D., Johnston, D.T., O’Hanlon, N.J., Balmer, D.E., Frost, T.M., Harris S.J. & Baker, H. 2023. Highly pathogenic avian influenza in wild birds in the United Kingdom in 2022: impacts, planning for future outbreaks, and conservation and research priorities. Report on virtual workshops held in November 2022. Research Report no. 752. British Trust for Ornithology, Thetford ISBN: 978-1-912642-47-2 92pp
Clewley, G.D., Cook, A.S.C.P., Davies, J.G., Humphreys, E.M., O’Hanlon, N.J., Weston, E., Boulinier, T. & Ponchon, A 2022. Acute impacts from Teflon harnesses used to fit bio-logging devices to Black-legged Kittiwake Rissa tridactyla. Ringing & Migration View at journal website (DOI: 10.1080/03078698.2022.2151065)
Langley, L.P., Bearhop, S., Burton, N.H.K., Banks, A.N., Frayling, T., Thaxter, C., Clewley G., Scragg, E. & Votier, S.C. 2022. Urban and coastal breeding lesser black-backed gulls (Larus fuscus) segregate by foraging habitat. Ibis View at journal website (DOI:
Booth Jones, K., Thaxter, C., Clewley, G., Wolsey, S., Calbrade, N., Atkinson, P., Calladine, J. & Burton, N. 2022. Belfast’s urban gulls: an assessment of breeding populations, breeding season movements and winter population. Research Report no. 734. British Trust for Ornithology, Thetford ISBN: 978-1-912642-26-7 52pp
Clewley, G.D., Calbrade, N.A., Austin, G.E., Frost, T.M. & Burton, N.H.K. 2022. A review of the BTO/RSPB/JNCC Wetland Bird Survey (WeBS) Low Tide Counts scheme with recommendations for its future operation.. Research Report no. 744. British Trust for Ornithology, Thetford ISBN: 978-1-912642-35-9 52pp

Other Publications

Clewley, G. D., & Wright, D. J. 2014. Winter hosts of Aphalara itadori (Hemiptera: Psyllidae), a classical biological control agent of Fallopia japonica (Polygonaceae), in the UK. Biocontrol Science and Technology, 24, 1197-1201.
Clewley, G. D., Eschen, R., Shaw, R. H., & Wright, D. J. 2012. The effectiveness of classical biological control of invasive plants. Journal of Applied Ecology, 49, 1287-1295.

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