Beebe remained active well into his old age. In 1957, at the age of eighty, he was still capable of climbing slippery tree trunks to study bird nests. However, by 1959 his strength had lessened enough that long hikes and tree climbing were no longer practical for him, and he contented himself with work that could be conducted in the laboratory, such as dissecting birds' nests to analyze their method of construction. Beebe also began to be afflicted with a throat ailment which may have been Sjögren's syndrome, although lacking a complete understanding of what caused it, Beebe and his doctors referred to it as "mango mouth". Beebe was reluctant to accept speaking engagements because of the effect this had on his voice, although he continued to give lectures on occasion with Jocelyn's help.