David Seel studied Zoology at Queen Mary College, London, before joining the Edward Grey Institute as a research student in 1960, where he conducted research into the breeding biology and molt of house sparrows and tree sparrows in Wytham Woods, eventually completing his thesis The Breeding Ecology of the House Sparrow (Passer Domesticus).

In 1965 Seel took up the post of demonstrator in Zoology at the University College of Wales, Aberystwyth, later going on to work in the Zoology Department at the University of Southampton, before moving on to the Bangor Research Station of the Institute of Terrestrial Ecology, where his principal area of study was on European cuckoos and fluoride concentrations in birds of prey. In the late 1980s he moved to the computing laboratory at the University College of North Wales, which was the last post he held before his death.