Extract of a letter, regarding swallows in winter from Armand Dubourdieu Dubourdieu describes the way in which swallows (Hirundinidae) 'drown' during the winter, remaining in the water until spring. He describes how the birds rest together in the water, one on top of another. Subject: Zoology / Ornithology / Natural history Written by Dubourdieu in Stockholm Read to the Royal Society on 27 October 1697 21 September 1697