The Thin Eggshell Years: teacher key

Peregrine Falcons, grade 11 edition, written for 11th grade. In the middle of the 1900s, peregrine falcon numbers fell as DDT thinned their eggshells. Follow the numbers down, and then the long work that brought them back.

Read the book. Print this page for the key.

Questions and answers

1. What did DDE prevent during eggshell formation?
   • Egg laying
   • Normal calcium deposition (answer)
   • Nest building
2. What was the all-time low in North America in 1975?
   • 1,650 nesting pairs
   • 39 nesting pairs
   • 324 nesting pairs (answer)
3. When were the first captive hatches at The Peregrine Fund?
   • 1973 (answer)
   • 1999
   • 1965
4. How did the recovery goal compare with the count?
   • The count was below the goal
   • 1,650 pairs was well above the goal of 631 (answer)
   • The goal was never set
5. Why did the number of peregrine pairs decline?
   • Falcons left the continent
   • Cities grew
   • Thin shells led to high reproductive failure (answer)
6. What does delisted mean here?
   • Taken off the endangered list (answer)
   • Moved to a zoo
   • Counted again

Words

• DDE: DDT breakdown product
• calcium: shell mineral
• incubation: egg sitting
• fledged: learned to fly
• delisted: taken off list