Can you clarify an argument within our family. We had two female blackbirds on the lawn at the same time, during our hour this morning and then about 20 mins later we had two male blackbirds, still within the hour. Should we record this on the sheet as two or four as there have been four distinctly different birds (2 male 2 female) or two as thats all that were there at any time?
Thanks Ian
I'll have to guess a number then for my tribe of sparrows - they change places on the feeder so rapidly that it's near impossible to see who's who!
No worries, on really busy gardens and feeders with flocking birds popping in and out all over the place an estimate is often the best you can do, that's fine by us!
Warden Intern at Otmoor.
Ian H said:Ok, we don't say this in the instructions, maybe we need to in future years, but the principle of counting the highest number seen at any one time is open to some interpretation in sexually dimorphic species (where males look different to females). So if you can be sure that you have seen 4 different individuals of one species (as in 2 male and 2 female blackbirds), please count 4 instead of 2.
Although getting people involved with birds is the main aim of the BGBW, this should definitely be reconsidered, and then clarified in the instructions for future BGBWs.
As has previously been said in this thread, counting the maximum number of individuals known to have visited the garden for sexually dimorphic species, but only the maximum number of individuals recorded at any one time for species with less clear cut differences between the species, will very clearly bias the results in favour of the sexually dimorphic species (perhaps even raising them above more numerous species in the "top ten/twenty" tables).
Recording only the maximum number seen at one time, even if you know you had two males at one time and two females at another, removes this bias and is the only simply way to allow a fair comparison between numbers of different species (and it's an easy instruction to include and follow).
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In the Natures Voice Magazine that is sent out, when its time for the bird count, the sheet that is sent out allowing you to mark off what species you see in the count has both female and male listed seperately for species that you can tell the difference in sex. Blackbirds, Chaffinches and Sparrows easy to tell the difference. So you would count as you seen them if it was obvious and then count the highest number on any other species seen during that hour.
Having two female Blackbirds say at the beginning of a count and 2 male Blackbirds near the end, and only counting them as two is allowing for an inacurate count. If everybody taking part in the BGBW did this then numbers on these species would dwindle by as much as half.
If you spend time keeping track of bird numbers in your garden and you are used to the patterns when it comes to numbers of species that visit your garden, then its more down to common sense.
Common species like Starlings, very difficult to tell sex apart, record the highest number seen at any one time, and this goes for all other species that visit the garden in high numbers do the same. Chaffinches and Blackbirds in my experience visit gardens in much smaller numbers than the larger birds, so makes it easier to keep track of the numbers.
Although is the BGBW also done to keep track of habits of our Garden birds at certain times of year and not just how many there are in number??
Unknown said:Roy, obviously the RSPB is running it, so I'm sure they'll answer officially.
Yes, it's entirely up to the RSPB, and i am well aware that the BGBW is not really about getting an accurate comparison of numbers of the species that visit gardens over the weekend. One important consideration is keeping it simple though - and personally I don't see what can be simpler than recording only the maximum number of a species any any given time during the hour - however old you are!
LostnSpace2011 said:Having two female Blackbirds say at the beginning of a count and 2 male Blackbirds near the end, and only counting them as two is allowing for an inacurate count. If everybody taking part in the BGBW did this then numbers on these species would dwindle by as much as half.
Yes, if you only count two in this case you are only counting half of the number that you know have visited the garden. It may not give an accurate indication of the actual number, but it allows a better comparison with the numbers of other species. For example, you may only see two Blue Tits at any one time, and because you can't tell them apart will only record 'two' - although you may have had ten individuals visit during the hour (while in the case of the Blackbirds it may have only been four individuals, but could have been more).
Common sense to me would suggest that it is better to have one rule for all species (ie. record the maximum number present at one time). It won't give you at accurate figure of how many individuals actually visited, but it doesn't give a bias to any particular species.
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Anyway, as said, it's up to the RSPB .
Unknown said: For example, you may only see two Blue Tits at any one time, and because you can't tell them apart will only record 'two' - although you may have had ten individuals visit during the hour (while in the case of the Blackbirds it may have only been four individuals, but could have been more).
For example, you may only see two Blue Tits at any one time, and because you can't tell them apart will only record 'two' - although you may have had ten individuals visit during the hour (while in the case of the Blackbirds it may have only been four individuals, but could have been more).
Agreed Roy :)
Hi Top Cat.
count only how many were in the garden at one time, there the same species so its two.
Thats not what it says here Sarah and it doesn't mention about sexes either.www.rspb.org.uk/.../how.aspx