Tom Stehn Reports from Aransas: February 26, 2002 Dear Journey North, Tom Stehn and Survey Plane Depending on how you want to calculate it, the whooping crane population this winter has either decreased or stayed the same. This is an example of the way in which numbers and facts can be presented to provide different conclusions. Let me explain: Only during winter at Aransas is it possible to get a total count of the whooping crane population. This is done by flying transects ina small airplane over a 35-mile section of salt marsh along the Teas coast until all the birds are located. This winter, 176 whooping cranes returned to Aransas. This is four birds less than the peak size of the population last winter: 180. But instead of comparing peak winter populations, let's look at the size of the flock in the spring of 2001 compared with spring 2002. During the 2000-01 winter, 6 whooping cranes died at Aransas, leaving 174 in the flock in spring 2001.As of right now on the doorstep of spring 2002, the flock also numbers 174. That is becuuse two of the 176 returning cranes died after arriving at Aransas this fall. So I like to think the population has broken even over the last 12 months (spring 2001 to spring 2002). Yet the traditional way of accounting for the whoopingc rane population would indicate a decrease of 4 birds this winter. Of the 52 adult pairs that nested in Wood Buffalo National Park in the Northwest Territories of Canada, only 15 brought a youngster with them to Aransas. Nesting success was definitely below average. Since the population didn't increase, that means at least 15 adult cranse died in the last year. I estimate 13 died between spring and fall 2001, and another two died this winter. So that negates the addition of 15 chicks to the population. Two single adult families (one adult plus one chick) arrived at Aransas this fall, indicating the loss of one adult since August. We believe most mortality of whooping crane adults occurs during migration. It is definitely the period when cranes are most vulnerable. Can you explain why that is? Copyright 2002 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form