Advocate Editorial Board opinion: Crucial to know number of birds in refuge
By the Advocate Editorial Board
March 6, 2013 at 6:02 p.m.
Updated March 5, 2013 at 9:06 p.m.
The count is in. This year, the U.S. Fish and Wildlife Service estimates there are about 279 whooping cranes in and around the Aransas National Wildlife Refuge. This year's estimate was gathered using a new method of counting.
In the past, the flock was counted by Tom Stehn, the former whooping crane coordinator, who started conducting surveys in the early 1980s. Because the flock was smaller, Stehn could fly over the refuge and count each individual bird. As time passed and the flock grew, he grew more experienced. But Stehn retired in 2011, and the wildlife service decided it was time to change the counting method.
Now, instead of trying to count every bird, the service uses a method known as hierarchical distance sampling, which can be adapted and reproduced, no matter who is doing the counting. This year's count estimates there are about 257 birds living on the refuge with a 95 percent confidence interval, meaning the actual number could be between 178 and 362 whoopers, with another 22 birds estimated living off the refuge.
The flock of whooping cranes is an important piece of the Gulf Coast ecosystem. This flock of endangered birds was found in 1938 on the brink of extinction. Their numbers have slowly grown over time, but they are still a long way from danger. This is why it is so important to have a consistent counting method that can be easily used by anyone either at the Aransas refuge or in Canada, where the flock spends the summer season.
The new method of counting makes sense when considering the growing size of the flock. As the number of birds increases, it becomes harder and harder to get an exact count of every single bird. However, this year's estimate has an interval of 184 possible birds between the highest and lowest estimates. This wide of a margin makes it difficult to know if the population is increasing or decreasing, which is important information when trying to protect an endangered species.
Because this is the first year the method was used, we understand there are some adjustments that can be made to improve the estimate's accuracy. As time goes by, those responsible for the count will be more knowledgeable and better equipped to offer an estimate with a narrower margin. We understand the need to improve the system as time goes by, but we wonder why the wildlife service did not consult with Stehn when developing the new counting method. It seems strange that the service would not take advantage of the decades of knowledge and experience this man has in this important effort to protect and cultivate the population of whooping cranes.
However, now that the system is in place, we hope the service will be able to increase the system's accuracy and provide a consistent count in the coming years.
This editorial reflects the views of the Victoria Advocate's editorial board.