But the $64m dollar question is whether there is any correlation between early arrival dates in the data shown above and cold winters?

I saw 7 swans flying over Bathgate, West Lothian in Scotland, yesterday morning when I was on the train waiting to go into Edinburgh.
Actually, I was stuck on the train for two and a half hours, due to a breakdown in front of us, which was due to an electrical failure on the line - on the day the new station was opened (with brass band, transport minister and all)! However, if it wasnt for that, I wouldnt have seen the swans and it was a lovely site - so thank you Scotrail! And It's certainly rather chilly today, by the way.

Agreed Trilobyte, wouldn't have been much more of a step to include lowest average temperatures for each year in that table at the end.

Anyone got time to download the data and make the graph?

If we assume that Trilobyte's question above is answered yes, this still leaves us with the question of what the mechanism is that would link the early arrival of Swan's with a colder UK winter.

Generally, you will get a colder winter in the UK when the winds come from the north and east, as they did last year, rather than from the south and west, as they did a few years previously. Given that the swans are flying from Siberia, to our east, it stands to reason that they will arrive here sooner if the winds are coming in the same direction. However, I'm not sure that translates into the same wind pattern persisting for the whole winter.

Alternatively, an early start to cold temperatures in Siberia might prompt the swans to set off earlier - but it can often be anomalously warm in Siberia while it is cold over the UK, so that doesn't necessarily say anything about temperatures here.

I'm glad that Slimbridge have got their swans in the news, but the story looks a bit rubbish. Last year the swans arrived on 31/10, which looks like a fairly late date for what turned out to be a cold winter.

Yes the "weather" link at the end actually leads back to this article. Where's a proper webeditor when you need one? Can I bid for the job?

What prompts migration? Falling temperatures where they are coming from, how well the food supply produced over the summer holds up and favourable winds are known factors. Most winter migrants move around according to temperature and food supplies across their winter range, it tells you only that the weather here and now is better than the alternatives, i.e. Siberia..

As far as this dataset goes, it's the first arrivals. That's a selection of outliers almost by definition. It would be much more meaningful if you knew the median arrival date. Or practically, when a substantial proportion of the total have arrived, say 2000 or 4000.

Well done WWT getting in the news, maybe even a boost to visitor numbers but it means very little.

Agree with all you've said, ThermoStat, but I'm wondering, what are you set to do in the cold - shut down or open up? And can you feel the moment coming on....

Indeed - median arrival date, CET and the temperature record from the area from which they migrated would be the plot to generate.

Eyeballing this first arrivals versus mild or cold UK winters that I recall shows no relationship as such, but that's the danger of eyeballing and using outliers!

Cheers - John

Response to johntherock 21 December 2011 09:05AM

Hi, I endorse these interesting comments ! Grauniad and WWT can we have some proper analysis please; simply supplying a spreadsheet which is hard to interpret is a bit lazy is it not WWT; can the WWT Press Officer not follow the feedback from 2010 and act on it in 2011?

Arctic swans arrival: when did the first Bewick's get here?

The superfluous apostrophe....

Is there a trend in this data? If there is I can't see it.

portergate, the swans are named after Thomas Bewick. So the apostrophe is not superfluous.
Somebody above has written "swan's" though.....

Reviewing the data involves accessing the link, exporting as an Excel file, then converting the dates from text to a numerical format that can be plotted on a graph.

Conclusions:
The arrival date for 1964 is so far out from the others that you need to be sceptical. It is very likely to be an entry error, so that the correct date could be 4th November. Alternatively of course, weather conditions could have been exceptional that year.
Then the range is between 12 Oct (1980) and 9th Nov (1967), 28 days.
A straight trend line (automatically generated in Excel) shows a trend of minus 3 days (‘earlier’) over the 48 year period. This trend is mainly due to the ‘late’ dates of 1967 and 1969. From 1970 onwards, there is no observable trend. But as is common with such data, you can show a trend in either direction or ‘no trend’, depending on the specific start and end years you choose. In any case, the trend would be small compared to the range, so main conclusion is ‘no trend’.
This is just from looking at these limited data. The next step would be to compare with temperature or weather conditions.
(I have not posted a graph to Flickr as this seems fiddly. May get round to it later)

When I get my place among the Guardians of Future Generations swans will arrive on time as will trains. The deniers have no future.

I did a quick plot and agree with you, it's too noisy to draw any conclusions.