The U.S. Fish and Wildlife Service reported the death of the first whooping crane this season at Aransas National Wildlife Refuge on Monday.

The body of the endangered bird was found after scientists noted that the radio transmitter attached to its leg was not moving from its established territory on Matagorda Island.

“It could have been predation,” Refuge Manager Dan Alonso said. “It could have been a multiple of things.”

The results of the necropsy are not expected for several weeks and will likely not be conclusive, but the death of a crane this early in the wintering season does not bode well for the rest of the flock, said former refuge biologist Tom Stehn, who monitored the cranes at the refuge from 1982 until his retirement this fall.

The marshes the birds depend on for their winter forage are in one of the worst droughts on record. The water has a high salinity and the cranes' preferred food source, blue crabs, are scarce, according to refuge reports.

“I've run across that combination seven times in the last 20 years, and all seven times there was higher than average crane mortality,” Stehn said. “That is not putting the finger on the causation, but it is certainly saying this is not good conditions for the cranes this winter.”

Aransas is home to the only self-sustaining flock of whooping cranes in the world. A count to determine this year's population has not been done, but it is expected to be around 300 birds, Alonso said. That would be an all-time high for the species since recovery efforts started in the 1930s.

The crane's death comes as a federal court case 40 miles away in Corpus Christi is under way to decide if Texas is doing enough to assure freshwater inflows into the marshes the cranes depend on.

That case is expected to be resolved by next week and could result in substantial changes to how water from the San Antonio and Guadalupe rivers is allocated.