1. Your calculations are a prediction
Your calculations are a prediction... How do we know how many there really are?
Actually count them all!
• US census
• ADA at school
• Giants game attendance
Count evidence of each!
• Nests
• Scat
• Prints

2. Sample the population Quadrat – a square area
Transect – a line through an area

3. Sample the population Mark and recapture
Catch a group, mark them, release; Capture a second group, count #
marked vs unmarked
Infer total based on number
marked in second sample