Prior to moving to India, he conducted some experiments to examine if cuckoo eggs (or more generally foreign eggs) were detected and removed by the hosts by placing eggs of one species in the nests of others.
Antes de ir á India realizou algúns experimentos para comprobar se os ovos do cuco (ou, máis xeralmente, ovos estraños) eran detectados e eliminados polos hospedeiro ao colocar ovos dunha especie nos niños doutras.