Letter from the 5th Earl of Cranbrook to Dr John A. Ledger asking him if he had received his reprints. He also mentioned he had collected specimens of Mallophaga from Collocalia gigas and wanted a safe way to send the specimens to him

Letter from the 5th Earl of Cranbrook to Dr John A. Ledger informing him he was sending him two reprints on swiftlet taxonomy. He advised him that Jacobson's collection was likely to be in Leiden. He also advised on the specie of a swiflet. He also stated he had sent the Mallophaga specimens to Dr Clay

Letter from the 5th Earl of Cranbrook to Dr Jorgen Randers, Deputy Director General, WWF International, enclosing the Earl's proposal to monitor urban swallow roosts in Sarawak

Letter from the 5th Earl of Cranbrook to Dr Kenneth C. Parkes enclosing two reprints. He stressed that swiftlets should be collected together with their nests to aid identification of species. He discussed several species of swiftlets

Letter from the 5th Earl of Cranbrook to Dr Kenneth C. Parkes on species of swiflets in the Phillipines and Malaysia

Letter from the 5th Earl of Cranbrook to Dr Nengah Wirawan requesting for international grant assistance for his group's visit to various places in Indonesia

Letter from the 5th Earl of Cranbrook to Dr Paul Hensen (Aarhus University. Natural History Museum. Bio-Acoustic Laboratory) on clicks uttered by avian embryos and possible mechanisms

Letter from the 5th Earl of Cranbrook to Dr Richard Schodde concerning the nest of Collocalia hirundacea which was found to have salivary cement. That contracdicted the only previous description. The Earl asked if the finding could be included in a forthcoming paper on the nests and eggs of New Guinea birds

Letter from the 5th Earl of Cranbrook to Dr Richard Schodde enquiring about Aerodramus papuensis and the nest of Collocalia hirundacea

Letter from the 5th Earl of Cranbrook to Dr S. Dillon Ripley concerning Ripley's remarks on C. vestita in Ripley and Rabor, 1958, A Collection of Birds from Mindoro Is.