Is the pattern of rarities changing?

Published on 10 June 2013

Just an observation: As part of my method to keep an check on submissions coming in to BBRC I have an expected  pattern of numbers (of rare birds) that will occur in each month, based on what has happened in previous years. Then as records come in I can compare the number expected with what has occurred to see if things need chasing. This year I have noticed a fairly big change in the actual pattern to that expected. Normally the early winter months (Jan to Mar inclusive) would produce about 3% of the year’s records each month, so 9% for those months in total. In 2012 Jan to March produced close to 14% which is 50% more than would be expected. April & May were as expected adding another c. 19% of records. June & July were much less than expected providing around 9% of records when they have historically produced around 14% – a sort of mirror image to those early winter months. August & September were similarly down, producing 23% of records when they would normally produce 31%. October & November were exactly as per normal, producing some 28% of records. And then December has jumped up with twice the expected number, normally giving around 2% but in 2012 providing 4% of the records.

So all a bit boring but if looked at as a big picture, is there something interesting buried in there? If we split the year into 4 sections the changes seem more stark:

Dec, Jan & Feb March : normally 11% of records, but in 2012 over 18% so a 65% increase

April & May : Normally 18% and in 2012 20%, so no significant change

Jun, July, August & Sept : normally 43% of records, but in 2012 only 33% a 25% decrease

Oct & Nov : normally 28% and in 2012 still 28% so no change

OK I know the December here (at the end of 2012)  is not contiguous with the Jan-Mar (beginning of 2012) but has the high number of rarities reported in December 2012 continued with high’ish number in Jan, Feb, March this year? I don’t know as relatively few records will yet have come in to me, and I don’t follow the rarity scene slavishly, preferring instead to get away for some winter warmth J. And of course the pattern will depend on the species that are involved and 2013 will lose Glossy Ibis records, but they are heavily concentrated in September to December.

So I am not drawing any conclusions at all, except maybe saying that those cold winter months are getting better for finding rarities. And knowing statistics probably 2013 will change again . Nigel Hudson. BBRC Secretary