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An Automatic Count of a Flock of Linnets (Carduelis
cannabina) in Flight over Stubble Fields at Angle,
Pembrokeshire, Wales
In autumn and winter, sizeable flocks of farmland birds present a challenge for bird
recorders. These flocks, which often comprise several hundreds of small, groundfeeding birds, are typically difficult to see or count while feeding on the ground.
These flocks are dense, very mobile and easily disturbed. Furthermore, the flocks
often comprise several different species, typically involving larks, sparrows, finches
and buntings. In flight, if there is a mixed flock of several similarly sized species, a
manual count is will be the most appropriate option. However, an automatic count
is also possible if it is a single-species flock and the birds are not too densely packed.
Text Box 5 outlines the process and settings used to carry out an automatic count
of the birds in Fig. 4 in ImageJ. This automatic count generated a total of 377 birds,
Text Box 5: The Process and Settings Used for Carrying Out an
Automatic Count of a Flock of Linnets in Flight over Farmland (Fig. 4)
Open ImageJ, select ‘File’ ➾ ‘Open’ – and choose the image that you want to
analyse
When the image is open select ‘Image’ ➾ ‘Type’ ➾ ‘8-bit’
Then, again under the ‘Image’ menu select ‘Adjust’ ➾ ‘Threshold’ – this
will open a box containing the Threshold settings
Then select the appropriate Threshold settings, which, in the case of the
image of the Linnets in flight, were as follows:
Top slider
– 92
Bottom slider
– 255
Default
– Red.
Tick
Dark background’
Click on the apply button twice
Then go back to the main ImageJ toolbar and select ‘Analyze’ ➾ ‘Analyze
particles’ – this opens another box and the following settings were selected:
Size (pixel)
500- infinity
Circularity
0.00–1.00
Show
Outlines
Tick
Display results
Click on OK
This will generate an Excel spreadsheet with the count details and an
image labelled ‘Drawing of + file name’ this shows the outlines (numbered)
of the Linnets that contributed to the count total.
Improving the Accuracy of Bird Counts Using Manual and Automated Counts…
An Automatic Count of a Flock of Linnets (Carduelis
cannabina) in Flight over Stubble Fields at Angle,
Pembrokeshire, Wales
In autumn and winter, sizeable flocks of farmland birds present a challenge for bird
recorders. These flocks, which often comprise several hundreds of small, groundfeeding birds, are typically difficult to see or count while feeding on the ground.
These flocks are dense, very mobile and easily disturbed. Furthermore, the flocks
often comprise several different species, typically involving larks, sparrows, finches
and buntings. In flight, if there is a mixed flock of several similarly sized species, a
manual count is will be the most appropriate option. However, an automatic count
is also possible if it is a single-species flock and the birds are not too densely packed.
Text Box 5 outlines the process and settings used to carry out an automatic count
of the birds in Fig. 4 in ImageJ. This automatic count generated a total of 377 birds,
Text Box 5: The Process and Settings Used for Carrying Out an
Automatic Count of a Flock of Linnets in Flight over Farmland (Fig. 4)
Open ImageJ, select ‘File’ ➾ ‘Open’ – and choose the image that you want to
analyse
When the image is open select ‘Image’ ➾ ‘Type’ ➾ ‘8-bit’
Then, again under the ‘Image’ menu select ‘Adjust’ ➾ ‘Threshold’ – this
will open a box containing the Threshold settings
Then select the appropriate Threshold settings, which, in the case of the
image of the Linnets in flight, were as follows:
Top slider
– 92
Bottom slider
– 255
Default
– Red.
Tick
Dark background’
Click on the apply button twice
Then go back to the main ImageJ toolbar and select ‘Analyze’ ➾ ‘Analyze
particles’ – this opens another box and the following settings were selected:
Size (pixel)
500- infinity
Circularity
0.00–1.00
Show
Outlines
Tick
Display results
Click on OK
This will generate an Excel spreadsheet with the count details and an
image labelled ‘Drawing of + file name’ this shows the outlines (numbered)
of the Linnets that contributed to the count total.
Improving the Accuracy of Bird Counts Using Manual and Automated Counts…