2. Numbers of birds in flocks Manomet Center for Conservation Sciences

4. 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

5. People differ in estimating tendencies Many tend to under estimate numbers Many tend to over estimate numbers Rare individuals tend to be accurate !

6. 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)

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

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

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

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

11. An estimating strategy If guess was 20 - 100, count 10 birds and then estimate by blocks of 10 for remaining < 20, count the birds 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,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

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

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

14. The guessed number should exceed 100 So, mentally block off 25 birds By blocks, extrapolate flock size How many black?How many blue?9690

15. 1. Guess the number

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

17. 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 R