Tom Stehn's Report: Important Discovery
March 6, 2009

As you read Tom's report this week, look for answers:
  1. What three things are causing troubles for cranes on the Texas wintering grounds?
  2. What is known about IBD? What is unknown?
  3. What is one good thing about pinpointing (identifying and isolating) the IBD virus at Aransas?

Dear Journey North,

Tom Stehn carries a juvenile crane too weak to stand to veterinarian help in Port Lavaca, TX.


This week we discovered that a rare disease has likely caused some of the 18 crane deaths here this winter.

The necropsy report on the juvenile we picked up in January in Dunham Bay tested positive for Infectious Bursal Disease (IBD). The virus was found in 2002 in a few of the cranes released into the nonmigratory flock in Florida, but this is the first time the virus has appeared in the Aransas flock.The Aransas cranes may get exposed and have to deal with IBD.

What are the unknowns of IBD? We have no idea how this Aransas IBD may be affecting the cranes, since the virus from the Aransas juvenile is a different type than the Florida virus. IBD is one of those things about which not much is known — except that it can devastate flocks of domestic chickens. We don't know how common or uncommon it is, or how it affects most wildlife populations.

If there can be a bright side, it's that we are learning something. The Health Lab* was able to isolate the virus. This means they can now try to grow it, test it, and take pictures of it. (No one had ever been able to isolate IBD from the Florida cranes before.)

The presence of IBD at Aransas this winter emphasizes the importance of having this endangered species living in at least two flocks, with those flocks too far apart to mingle.

Meanwhile, the blue crabs will come back into warmer waters as March brings warmer temperatures. The cranes will be glad to eat their favorite food again as they prepare for their journey north to Canada.

Tom Stehn
Aransas National Wildlife Refuge
Austwell, Texas

*US Geological Survery National Wildlife Health Lab