Letter

SIRS,--For some years past, Mr. Charles Oldham has regularly published observations on t h e midsummer movements of Swallows, House- and Sand-Martins and Swifts at t h e Tring and Elstree Reservoirs in t h e Transactions of the Herts Nat. Hist. Soc. An idea t h a t t h e birds seen at Tring, sometimes in very large numbers, at t h e end of June or beginning of July are not on passage b u t merely ...