When does a Common Swift become a Pallid?

I have to ask the question, and not because I disbelieve that there are Pallid Swifts in our skies. It seems that for the past few years, any lone swift seen above our fair country in the late autumn has as much chance of being a Pallid as a Common. Are there Pallid Swifts in our skies much earlier in the autumn that are just not being picked up, mostly because there are plenty of Commons about? Are birders not conditioned to look for them earlier in the autumn? Does a lone, late autumn swift get grilled all the more  and so any Pallids present are not getting missed? And what about all of those late swifts from yesteryear? How many of those, that were passed off as Common, were in fact Pallid?

A few years ago, on November 28th, I was walking along a street in Sutton on a mild, heavily overcast day. I happened to look up just as a swift came into view, very low. It passed directly over me and I saw it very well. I was more than aware that there was a very good chance that it could be a Pallid, but it was just a Common. I was a little disappointed. I think that I was unlucky in the bird just being the 'common' species. I wouldn't mind betting that there was more chance of it being a Pallid that late in the year.

The past few days have seen a number of Pallids being found. I would be interested to find out how many Common Swifts are being reported at the moment. What is the ratio between the two species from mid-October onwards? Is any swift seen from late October onwards statistically more likely to be a rare one? I wonder what date Common Swifts become Pallid in the birders psyche?


laurence.d said…
I think it,s a totally normal situation,we are all hoping for that bird to be a rare,as you say you were a little disappointed that your Swift was a common,so anyone would look a bit harder at some species, at certain times of the year ,even tough the odds probably aren't much better,I remember saying to a friend that we should take a closer look at a common sand that he had picked up as it was mid October,and you know what,it was a spotted sand !.
Steve Gale said…
Your Spotted Sand incident proves the point, doesn't it Laurence. I'm sure plenty are missed earlier in the autumn, purely because of the date.

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