Number of Days on the Wintering Grounds
Eastern Flock, First Ultralight-led Cranes to Depart

The nine young cranes that departed Wheeler NWR in Alabama on April 12, 2012 have been on their wintering grounds since their February 4, 2012 arrival. How many days is that? Complete the chart by filling in the number of days the Class of 2011 spent on the wintering grounds.
 Year Days Spent on Wintering Grounds ( first birds to depart) Class of 2011s (Wheeler NWR) 0arday Class of 2010 96 days 0 days (St. Marks NWR) 80 days (Chassahowitzka NWR) Class of 2009 70 days (St. Marks) 75 days (Chassahowitzka) Class of 2008 72 days (St. Marks) 60 days (Chassahowitzka) Class of 2007 57 days Class of 2006 (Florida Storm: no survivors) Class of 2005 106 days Class of 2004 104 days Class of 2003 113 days Class of 2002 121 days Class of 2001 126 days

Journal or Discussion Questions
The number of days on the wintering grounds is calculated from the arrival date to the first bird's departure date.

1. What do you need to know in order to figure the average number of days spent on the wintering grounds for each group of birds?
2. What fact statements can be made using the data above?
3. What is the average number of days on the wintering grounds for all 11 years in which ultralight-led cranes have departed on spring migration?
4. What factors might explain the year-to-year differences?