Update from the Whooping Cranes' Winter Headquarters
This time I'm sure some of the whooping cranes have started the migration. During a census flight I did April 4th, I could only find 140 whooping cranes. Nine adult pairs were not found on their territories, a pretty sure sign they have left for the winter. I estimate that as many as 34 of the total of 174 in the flock, the current size of the flock, have headed north. The peak population during the 2000-2001 winter was 180. An estimated six whooping cranes died at Aransas this winter, leaving 174. This is quite a drop from the 187 whoopers in the flock in the spring of 2000. We can only hope for a reversal of this trend in 2001.
Most of these departures occurred April 2-3. Migration conditions were excellent on April 2, and two cranes were observed that day flying high over and the refuge and to the north. The Mustang Lake pair seen by visitors to the refuge from the public observation tower apparently headed out the morning of April 5. Weather forecasts called for strong southeast winds 15-30 mph with partly cloudy skies April 5-6, so many more cranes presumably left on those days. The majority of departures normally occur between April 4-12, so the whooping cranes seem right on schedule. Warmer temperatures are starting to spread throughout the mid-west, and it is time for the cranes to make their 2,500 mile journey up to the Northwest Territories of Canada.
Think about what conditions the whooping cranes need to make their migration easier. If you know these conditions, then you should be able to tell me if whooping cranes ever fly up through a thick cloud layer and migrate above the clouds. What would the advantages and disadvantages be? I'll give you my answer next week.
On my aerial flight, an oil slick about 1 1/4 acres in size was observed adjacent to the Victoria Barge Canal in the crane area. The slick could have come from a vessel pumping its bilges. The slick was reported to the Texas General Land oil spill response office in Port Lavaca, Texas, but by the time they got there no trace was found. That was not surprising since what I saw from the airplane was a very light, thin sheen of oil discoloring the water.
Fortunately, winds were pushing the pollution away from the crane marshes. I do worry about what a major chemical spill could do to the whooping crane habitat. But experts feel the chance of this is remote since chemicals are not unloaded or loaded onto ships or barges near whooping crane habitat. We do keep oil spill booms on the refuge to try to contain a spill if one occurs. Unfortunately, the boat traffic goes so close to the cranes that a spill could enter crane marshes before we would have a chance to respond. It is just another danger that a very endangered species continues to face as it fights to survive. Unfortunately, many species of endangered wildlife face similar threats as development and loss of wildlife habitat continues in this country and around the world.
I'm going to give the remaining whooping cranes two weeks to get on out of here. Why would some of the whooping cranes not be as anxious as others to leave? I won't fly again until April 17th to see what stragglers are left. I expect to find less than 50 birds remaining at that time.
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