posted August 11th, 2012; last edited August 20th, 2012 –– David Sibley

Quiz 46 – Estimating numbers

Estimating numbers in flocks of birds is a skill that birders need to practice, but we rarely get a chance to test ourselves. We see a flock, guess the total number, and write it down. We might be off by a large margin, but we’ll never know.

Here is a quiz (and more to come) that will give you a chance to test your accuracy. These are lentils, photographed against a white background, but they simulate birds pretty well, I think.

One estimating technique you can try is to count the “flock” in segments. That is, count ten to see what a group of ten looks like, then superimpose that group across the flock, counting in groups of ten. Or you can just “eyeball” the flock of lentils and take a guess. Good luck, and feel free to offer suggestions or encouragement in the comments.

Test your number sense

Question 1
A
60
Hint:
too low
B
90
Hint:
too low
C
110
Hint:
a little low
D
150
E
190
Hint:
a little high
Question 2
A
45
Hint:
way too low
B
60
Hint:
too low
C
100
D
140
Hint:
a little high
E
180
Hint:
too high
Question 3
A
50
Hint:
too low
B
80
Hint:
close, just a little low
C
100
D
120
Hint:
close, just a little high
E
150
Hint:
too high
There are 3 questions to complete.

12 comments to Quiz 46 – Estimating numbers

  • Mary Ann Preston

    This was good!! Keep em coming. & for future reference do not ask me to count birds this fall !!

  • Interesting… this is definitely a skill I could use some practice with.

  • Jennifer Ferrick

    Thanks for this, awesome idea… Anxious to see the other quizzes that will be arriving- the practice is needed & very much appreciated!!

  • Mike Heaney

    Good practice. Will be useful with CBCs coming up. Question #2 may have a glitch.

  • Chris Hill

    ARBIB, R. 1972. On the art of estimating numbers. Am. Birds 26:706-712

  • Scott Baron

    Thanks, Mr. Sibley. I also experienced a glitch w/ question 2. When I clicked on D there was no response. Then when I tried E a checkmark appeared.

  • Tim in Albion

    These are great exercises, and I really need to practice this skill. This is a cool way to do it.

    My only quibble: What level of precision is necessary? To my mind, there is no significant difference between the numbers 90 and 100 in this context. Even 100-120 are within the expected margin of error, I would think. If my estimates of birds in flight were regularly within 50% of the actual number, I’d call myself skilled enough. Am I setting the bar too low?

    • Hi Tim, Thanks for the feedback. I agree, if you’re getting within 50% consistently that’s pretty good. I did try to avoid making these quizzes too “nit-picky” with answer choices as close together as 90 and 100, so I’ve just fixed that one. I also added “hints” that show up to give instant feedback on which way you missed, as I think that is helpful also.

  • Mark, Biologist at CRP

    This is great! I regularly do waterfowl surveys and have volunteer citizen scientists that help. I have used these exercises for years to hone my skills and encourage my teams to do the same. The more precise the count the better the data… I guess I just like to set the bar high. One twist I like to throw at people (myself included) to challenge them is to use mix sizes and colors i.e. mixture of pinto beans, lentils, rice etc. tossed onto a gray background.
    These exercises are great because I don’t have to count them and I don’t have to pick up the mess.

  • Sue Ewan

    Thanks – this is a really good test and great feedback for knowing if we are getting better.

  • Very good. But it would be nice to have some with several thousand “birds”. Those are the tough ones!

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