Counting birds can seem daunting, particularly when they are in flight or in large, mixed groups. Luckily, there’s a couple of trusty techniques you can count on.
We’re asking everyone who is taking part in the Great Coastal Bird Watch to have a go at counting the birds they see on the coast, as the results will give us valuable information about how well different species are faring.
Here’s Ranger Alice’s guide to making the best estimates of the bird numbers you see:
It sounds like it should be easy. After all, most all of us know how to count – don’t we?
When it’s smallest cluster of birds, like this group of dark-bellied brents, it’s pretty straightforward.
But often we’re not encountering a small group of birds, and sometimes we spot hundreds or even thousands of them. Far more than you could possibly count one at a time.
We know that counting birds can seem challenging, especially when they group together in enormous flocks or take flight mid-count. However, help is at hand, and the important thing to remember is that estimates are just fine! Exact numbers are fantastic, but not always possible, and your best guess will always be far more useful than not attempting to count at all.
So, where do you start with a large, moving flock, like this group?
To work out the rough number of birds present, count one small section of birds (ten or twenty are good numbers to start with) and then visualise how many sections make up the flock. You can then use this to estimate how many birds there are.
For example, in the section highlighted by the red rectangle, I have counted around 20 birds. The entire flock can be covered by about 10 squares of a similar size, so I estimate the number of birds to be about 200. With some larger flocks, you may find it easier to group the birds in 50s or even 100s.
But what if the flock contains more than one species?
Firstly, use your handy ID guide to figure out what species are in the flock.
In this photo, I can see wigeon, pintail and a few teal.
Once you know what birds are present, have a think about what percentage of the flock each species makes up.
For example, I can see that wigeon are the most numerous species in the photo, and I estimate that they make up around 95% of the flock, with pintail making up about 5%. As there are only two teal in the flock, I’m going to count them separately.
Next, use the grouping method (the same one we used to count the number of godwits in the first photo) to estimate the total number of birds. It looks like there are about 140.
Now it’s time for some quick percentage maths! If there are 140 birds, with 95% being wigeon and 5% pintail, then we have 133 wigeon, seven pintail and the two teal, of course.