Counting species

I used to do this, but I've changed my mind this year.  Here's my thinking.  When we record the maximum seen at any one time, what we are doing is a form of sampling.  In a comparative survey, sampling only works if we use the same sampling method for all species.  If we can't distinguish male and female blue tits, we shouldn't distinguish male and female blackbirds.  If we do, the results will always be skewed in favour of those species where the sexes are different.

Here's another example.  If I see three goldfinches at three different times during my hour, the total number of birds seen could be anywhere between 3 and 9, so I record 3.  If I also see three chaffinches at three different times, but the first time they are all male, the second time they are all female and the third time they are mixed, the total birds seen could be anywhere between 6 and 9.  In the past I would have recorded 6.  But have I seen twice as many chaffinches as goldfinches?  Probably not.

I think we should just do what it says on the tin, and not try to be clever.

Well I'm not going to argue the point, but if everyone does this, then the figures for house sparrows, blackbirds and chaffinches will be vastly inflated in comparison with almost everything else.  Common sense and statistics don't mix!

I'm in complete agreement with Chesterfield on this.

If the maximum number visiting at any single time is what is being recorded for some species, then that is what should be recorded for all species - even if it is obvious that different individuals visit at different times.

This keeps the count as simple as possible, and allows a fairer comparison between species.

I participated in this event for the first time today, I did count male and female birds separately.  Eg during the whole hour, I had blackbirds flying in to the garden all the time, however, at any one time I saw the maximum of 2 males and 1 female, so I counted 3.  Again with house sparrows, I saw them fly in sporadically through the hour, but at most I saw 2 female and 1 male and so I again counted 3.  

I counted thus, as I was sure I saw 3 separate individuals.  It would be good to know if this was the correct point of view tho'.

I participated in this event for the first time today, I did count male and female birds separately.  Eg during the whole hour, I had blackbirds flying in to the garden all the time, however, at any one time I saw the maximum of 2 males and 1 female, so I counted 3.  Again with house sparrows, I saw them fly in sporadically through the hour, but at most I saw 2 female and 1 male and so I again counted 3.  

I counted thus, as I was sure I saw 3 separate individuals.  It would be good to know if this was the correct point of view tho'.

You should count it as 4 Blackbirds, as you have seen 4 different individuals. You're counting the minimum number of individuals in your garden in an hour, so if you know that you've seen 4, then count it as 4, not as 2 - that would be an under-count!

If you can't tell males and females apart (e.g. long-tailed tits), then just count the maximum number that you see together at any one time, as that is the most that you've had. It doesn't mean that birds with obvious differences between the sexes will be over-counted, as you're still counting the minimum number of individuals that you had in your garden in that hour.

I counted on the basis of type as well as sex, so my 4 blackbirds were 2 females that came together, and 2 males that came together, but not all at the same time. My 4 chaffinches were 3 female (all seen together) and one male, which came and went. Other species came in groups.

What really disappointed me was that I only saw 3 house sparrows in my hour, 2 male and one female, which all came together. I have had up to 30 at a time coming in to feed, so it looks as though there have been massive losses this winter. Even starlings were far fewer than I have often seen here - only 5,

Jenny - you may have seen fewer Sparrows and Starlings than you usually do, but there will also be people that have seen more than they usually do, so it all evens out in the end!

Unknown said:

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 for flagging this up with us Sue, i'll try to clear this up for you!

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.

Thanks for takling part!