When researching for "Birds of South Asia", Rasmussen examined tens of thousands of bird specimens, since the late S. Dillon Ripley had strongly favoured the use of museum specimens to determine which birds to include. With Robert Prys-Jones of the Natural History Museum, she showed that the decades-old Meinertzhagen fraud was far more extensive than first thought. Many of the 20,000 bird specimens in his collection had been relabelled with regard to where they were collected, and sometimes also remounted. The false documentation delayed the rediscovery of the forest owlet, since previous searches had relied on Meinertzagen's faked records. Rasmussen's successful expedition ignored these and looked in the areas identified by the remaining genuine specimens.