Colin Pennycuick worked in the Department of Zoology from 1964 to 1968 and from 1973 to 1983. More recently he was an Honorary Professor and Research Collaborator in the School of Biological Sciences.

Colin was an international expert on animal flight, and combined his drive for understanding how animals work with a passion for flight. He developed novel models to understand flight mechanics, for example to predict the optimal animal flight speeds. He would then test his model predictions by developing innovative methods to measure flight speeds and following birds in his light aircraft.

Colin was born in Windsor, Berkshire in 1933. He pursued his undergraduate studies at Merton College, Oxford where he joined the Oxford University Air Squadron. He completed his PhD at Peterhouse, Cambridge working on muscle physiology. After completing a research fellowship at Cambridge, Colin joined the Department of Zoology at Bristol as a lecturer in 1964.

At Bristol, Colin would perform innovative experimental work in sometimes remarkable situations. He used the University’s first computer to design a wind tunnel which became a feature in the stairwell of the Fry Building. Colin‘s experiments flying pigeons in the tunnel allowed him to apply fixed-wing aerodynamic theory to predict flight performance in birds. He made novel insights into understanding gliding flight and produced a classic ‘momentum jet’ model for animal flight mechanics. He also modelled limits to upper body size for flying birds and trade-offs between fat storage and migration range.

Colin moved to Africa in 1968 and used his Piper Cruiser aircraft to study bird flight in the Serengeti. He flew fruit bats in wind tunnels and went gliding with pelicans and storks to understand how birds used thermals for soaring. He flew the Piper Cruiser to Bristol, stopping off at Addis Ababa, Cairo and Crete, in the way that a migratory bird would. During his second spell at Bristol, Colin developed an ‘ornithodolite’ attached to a computer to measure the range, azimuth and elevation of flying birds.

He also studied the flight of cranes in Sweden, soaring seabirds in the Antarctic and performed aerial surveys of geese in Scotland and Ireland. At Bristol, Colin supervised PhD students performing pioneering flow visualisations of the air movements produced by flying birds and the links between wing shape and flight performance in bats.

Colin took up the position of Maytag Chair of Ornithology at Miami University after leaving Bristol in 1983.

Colin published Bird Flight Performance: a Practical Calculation Manual in 1989 and introduced researchers worldwide to his ‘Flight’ programme for calculating optimal flight speeds of vertebrates. The programme is still used widely today. While at Miami University, Colin was involved in some of the first studies using satellite tags to document the movement ecology of birds. He flew back to Bristol in 1992 in his Cessna 182. He collaborated extensively with scientists at Lund University in Sweden, where King Carl XVI inaugurated a wind tunnel that he helped develop.

Colin was always generous with his time and advised most of the leading students and researchers working on animal flight mechanics today. He was remarkable in his ability to draw on his love of flying to discover what it is like to be a flying bird. He was elected a Fellow of the Royal Society in 1990, and was made an Honorary Companion of the Royal Aeronautical Society in 1994.

Colin died on 9 December 2019 aged 86. He is survived by his wife Sandy, with whom he authored Birds Never Get Lost (published in 2016), and his son Adam, now a respiratory physician working at University College London.

Further tributes can be found in the Guardian and in the journal of the British Ornithologists’ Union, Ibis.