Numbers of birds in flocks

1. Estimating Numbers of birds in flocks  Manomet Center for Conservation Sciences

2. Do you know your estimating tendencies ?

3. Most field biologists think they are good at estimating numbers of birds in flocks, but • In fact, it is the rare person who estimates bird numbers with good precision • Periodic practice improves estimating abilities

4. People differ in estimating tendencies • Many tend to underestimate numbers • Many tend to overestimate numbers • Rare individuals tend to be accurate ! !

5. Estimating accuracy will tend to vary with: • The size of the flock (most people tend to underestimate numbers in large flocks) • The size of the birds (most people tend to underestimate numbers when birds are small and to overestimate when birds are large) • The color of birds (a tendency to overestimate when birds are light-colored versus dark-colored)

6. The size of the flock most people tend to underestimate numbers in large flocks Estimate the number of dots 15 How many birds? 837

7. The size of the birds How many Large ? Small ? Most people over- estimate numbers of large birds 40 each

8. The color of birds How many light and dark? a tendency to overestimate when birds are light-colored versus dark-colored 54 each

9. An estimating strategy • Guess the flock size • Is there more than one species? • Are birds fairly evenly dispersed ?

10. An estimating strategy If guess was • < 20, count the birds • 20 - 100, count 10 birds and then estimate • by blocks of 10 for remaining • 100 - 500, count 25 or 50, then ‘block count’ • the rest of the flock by 50’s • >500, count (estimate if flying) 100 and then • ‘block count’ the rest by 100’s , , , , , ,, ,,,, ,,, ,, ,,, ,,,,,,, ,, ,,,,,

11. An estimating strategy • Finally, estimate the percentage of each species in the flock Beware of estimates for flocks where birds are unevenly dispersed

12. 1. Guess the flock size 2. Is there more than one species ? 3. Are the birds fairly evenly dispersed ?

13. The guessed number should exceed 100 So, mentally block off 25 birds By blocks, extrapolate flock size How many black? 90 How many blue? 96

14. "Nightmare estimating" 1. Guess the number

15. Now, using the known ‘blocks’, estimate (you have 20 seconds) How about 3400 ? OK, What was your estimate?

16. R These exercises were to provide tips Each person will have different tendencies -- the goal is to learn your own … practice to learn them. Part 2 provides practice exercises You also can practice by counting 1/3 cup of beans or a teaspoon of rice. Grab beans (or rice), throw in a box top, estimate, then ‘count’ using cups-full (or teaspoons full). The end