Tom Stehn Reports from Aransas: April 16, 2003
Dear Journey North: Since the migration has started, 96% of the flock has headed north. I?m
pretty close to having an empty nest with just 7 whooping cranes to search
for next week. This is true in my own house also, with my two sons both
in college. The crane I have been watching all winter with the drooping left wing has apparently started the migration. This does not surprise me since it had migrated south last fall with the injured wing. The wing is not hanging down as far as it was earlier in the winter. It has gotten better, and the crane has been observed flying normally. Last week I asked you how cranes manage to spend 2-3 weeks migrating, and then 4 weeks nesting and sitting on eggs, with not enough time to spend finding food to eat. The answer has to do with fat reserves. Prior to the spring migration, the cranes gain weight, eating more and storing energy in the form of body fat. That is why it is so important to have lots of blue crabs available in the spring at Aransas to enable the cranes to build up these fat reserves. The cranes have to endure the hardships of long migration flights, feeding only a little each day in the morning and evening. Perhaps the cranes will get up to Canada when it is still frozen and find little to eat. Then they have to take turns with the male and female both spending time sitting on eggs and not having time to search for food. Through all these hard times, the cranes rely on their fat reserves and slowly use them up. In this way they can survive to make another migration and raise another young next year. Since most adult cranes nest every year, why do you think the whooping crane population has grown so slowly and is still endangered? Until my next update; enjoy the spring. Copyright 2003 Journey North. All Rights Reserved.
|