Thirty-seven demoiselle cranes were found dead at Khichan in Phalodi subdivision of Jodhpur on Thursday morning.
Three of the carcasses were sent to a vet dispensary at Machia Biological Park for a medical examination to ascertain the cause of their death.
According to Sevaram Mali, a bird lover, the migratory birds were found dead at different places.
"We received information in the morning that some birds have been spotted dead near Vijay Sagar. When we reached there, we found 15 carcasses," said Mali.
Later, they received information about the death of more birds near Ratari Nadi.