April 1953 – vol. 46, issue 4–152 SIRS.--I am trying to collect information about ultra-quiet bird song (sub-song, etc.) and I should be grateful if you would allow me to appeal through the medium of British Birds for any help that other observers can give me. As records on this subject are a p t to be rather long, I should be most grateful if anyone having notes on very quiet song would, in the first place, be kind enough to send... This article is only available to registered users.To read more, please log in or purchase a subscription.