Their parents were Caroline Mary (born Drummond) and John Houghton Bradley.

[1] In 1958 the sisters published "Notes on the Behaviour and Plumage of Colour-ringed Blue Wrens" in the peer-reviewed journal Emu, which described their work trapping and ringing 25 superb fairywrens from three different groups,[3] which they found in their garden and the nearby Ashton Park.

Joan was a trained chemist and they pointed out that organochlorine insecticides caused sterility in birds.

They saw that native plants needed time to take over land so they had to be careful to be gentle and to not proceed too quickly.

[6] Joan was employed by the National Trust of Australia in 1975 as they experimented with the Bradley method of controlling weeds at the Ludovic Blackwood Memorial Sanctuary in Beecroft.