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How do you count birds?

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Old Thursday 15th October 2009, 17:02   #1
Stoggler
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How do you count birds?

Sounds a silly question, but it's something that's puzzled me. For example, take this report on the Sussex Ornithological Society's page for recent sightings:

Quote:
Conditions looked excellent at Climping Gap this morning and observer coverage was good, but despite this nothing unusual was found. However, once again the visible migration was noteworthy, with flocks of finches all heading E along the coast (just where are they all going to?). Goldfinches again predominated, with a massive total of 2360 logged
How do people manage to log such a precise high number of a species of bird?

Also:

Quote:
however there were also at least 55 Linnets, 185 Siskins, 15 Redpolls, 15 Chaffinches, plus 30 Sky Larks and 77 Pied/alba Wagtails.
How do people manage to count flocks of birds this time of year so confidently, especially as I've read that many birds of different species form single flocks. There were three people on this birdwatch, how can three sets of bins/scopes manage to confirm that all the birds in a flock are of one species, or how do they manage to ID and count a mixture of species?

Here's the link to the site:

http://www.sos.org.uk/recent-sightings/index.php

Thanks
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Old Thursday 15th October 2009, 17:17   #2
Capercaillie71
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The first example you give is not too difficult as the birds are likley to be passing a fixed point in relatively low numbers for a certain length of time.

Large flocks together can be estimated or counted more accurately from photographs, but realistically there is always going to be a margin of error.

For me it starts to get a bit over the top when you see things like this:

"a spectacular roost count of 60626 [Pink-footed geese] were counted"

Not 60627, then!
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Old Thursday 15th October 2009, 17:40   #3
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Quote:
Originally Posted by Capercaillie71 View Post
The first example you give is not too difficult as the birds are likley to be passing a fixed point in relatively low numbers for a certain length of time.

Large flocks together can be estimated or counted more accurately from photographs, but realistically there is always going to be a margin of error.

For me it starts to get a bit over the top when you see things like this:

"a spectacular roost count of 60626 [Pink-footed geese] were counted"

Not 60627, then!
I would count a large flock in the following manner. Say, a medium sized field has a large flock of geese in it. I would count, say, 20 birds and then visualise the area covered by those 20 and see how many 'area's are covered by birds. If there are 25 such areas there would be approximately 20 x 25 = 500 birds. If the fields were larger, or the apparent total number of birds appeared to be much greater, I would use a bigger starting number - perhaps counting 100 birds.

Now to answer the question of the apparent exact number of birds. In my first example, I have estimated 500 birds in a field and then I note 16 birds (individually counted) in the next field thus 516 total birds.

In the example quoted, the figure of 60626 was probably made up of 60 lots of 1000 birds and then 26 others were found seperately or flew in after the estimate was made. The count 'blocks' of 1000 may have been estimated by counts of 100 using the same principle.

In my opinion, if I had estimated 60600 birds and another 26 flew in, I would probably ignore them or make a seperate note as the proportion of 26 to 60600 would probably be less than the plus or minus of the estimate.

Note also that in this case, birds may have been counted (perhaps in blocks of 20, 100 etc.) coming into the roost as opposed to settled in the roost site.

Hope you are all still with me!!
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Old Thursday 15th October 2009, 18:34   #4
Jim M.
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Quote:
Originally Posted by Stoggler View Post
How do people manage to count flocks of birds this time of year so confidently
Here are some great articles on how to count birds from the folks at eBird:

http://ebird.org/content/ebird/news/bird-counting-101

http://ebird.org/content/ebird/news/bird-counting-201

Hope this helps,
Jim
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Old Thursday 15th October 2009, 18:36   #5
Dave B Smith
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Quote:
Originally Posted by Capercaillie71 View Post
"a spectacular roost count of 60626 [Pink-footed geese] were counted"
I thought that "spectacular" referred to the feat of counting that many!
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Old Thursday 15th October 2009, 18:55   #6
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If you write down all numbers of birds, you can get reasonably reliable numbers. Birds in large flocks require practice and a lot of estimating (I usually count parts of a flock and then multiply this area).
When you count flocks as "100s", you should round off the number to the nearest 100, but not everyone does.
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Old Thursday 15th October 2009, 20:49   #7
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Quote:
Originally Posted by Dave B Smith View Post
I thought that "spectacular" referred to the feat of counting that many!
Lol, hats off to whoever can count to 60 thousand without dozing off in the middle...
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Old Thursday 15th October 2009, 20:56   #8
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Quote:
Originally Posted by Xenospiza View Post
If you write down all numbers of birds, you can get reasonably reliable numbers. Birds in large flocks require practice and a lot of estimating (I usually count parts of a flock and then multiply this area).
When you count flocks as "100s", you should round off the number to the nearest 100, but not everyone does.
I fully agree, and noticed that Colin at the very end said something to that effect also.

Let us also remember that the theoretical background for why you cannot add the last 26 if your counting consisted of blocks of 100 is taught in statistics, and statistics is not a requirement for being a bird counter

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Old Thursday 15th October 2009, 21:41   #9
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I use a digital tally counter when I'm out doing BTO surveys, however when faced with a big flock I use it to log the 20's I count, rather than each individual bird. When counting waders at rest I have used it to tally each individual bird and have been quite amazed at how many birds I've been looking at.
With practise you can become quite accurate with estimating small flocks at a glance, I'd a flock of waxwings visit my garden earlier this year and I guesstimated it at 200 birds, posted a picture of part of the flock (maybe 3/4s of the birds) and someone actually counted the birds in the picture and came up with 148 as the total, so I wasn't too far off.
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Old Thursday 15th October 2009, 21:49   #10
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Bill Oddie said that birders get obsessed with counting birds, I don't! Fortunately there are lots of birders who do. Its something that I need to improve on
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Old Thursday 15th October 2009, 22:10   #11
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I count bird in blocks. If I was counting a large flock of geese I'd count say 50 individuals, then I'd count 10 blocks of 50 and then work out how many blocks of 500 there are in the flock. That way I can get a reasonable estimate very quickly, within about a minute, even if it's a huge flock.

If I was counting hirundines I might do the same on a smaller scale. If it's a mixed flock I then estimate the percentage of each species in the flock. That way if I get to a count of 500 hirundines over a lake, of which approximately 10% are Sand Martins, 30% are House Martins and 60% are Swallows, this gives me approximately 50 Sand Martins, 150 House Martins and 300 Swallows.

Not exactly scientific perhaps, but close enough for me!
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Old Friday 16th October 2009, 09:29   #12
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The original posts also asked about counting more than one species in a flock. Keith mentioned using a tally counter which is what I use. With this, you can count one species with the counter and another in your head. Needs a bit of practice - bit like patting your head and rubbing your stomach at the same time!! Try it with say a couple of dozen ducks on the local pond to start. When you get really practiced, it is possible to use two tally counters and one head!! That's about my limit and then I am unable to walk and talk at the same time.
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Old Friday 16th October 2009, 10:12   #13
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Thanks for the posts everyone. I had used the counting of blocks myself, but it was the precise nature of the report that threw me - 2360 just seemed rather a precise number rather than say c2300 or c2400.
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Old Friday 16th October 2009, 13:45   #14
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What appears as very precise numbers in bird reports etc are usually estimates of large flocks with a smaller flock, that can be counted individually, nearby. I've been doing WEBs counts for nearly 30 years now, and have some huge counts of mixed flocks of waders, I normally count the whole flock then estimate the proportion of, say, Dunlin to Knot and work it out from that.
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