Wednesday, 2 April 2014

Where are all the Cormorants?

As many of you may know, if you follow me on twitter, I like to seawatch, partly because I can from my sofa and partly because I lived in Cornwall for 4 years which saw me cave in to the dark arts of seawatching! However, seawatching at Hemsby is a far cry from Pendeen or Porthgwarra! No longer am I counting shearwaters in their hundreds or thousands, seeing flocks of petrels etc. In fact I’ve only recorded 11 shearwaters and 2 petrels in the last 20 months off Hemsby. Autumn can still be good here with nice skua passages and wildfowl and waders passing through but for most of the year it is the common, the mundane birds that keep me going with the hope of a nice patch year tick along the way with 2014 delighting me with Red-necked Grebe, Black-throated Diver and some unseasonal skuas.
So to the common birds, it was in the early part of 2013 that I started taking a real interest in Cormorants. In January and February I was recording some really high numbers of Cormorants moving south with maximum counts of 913, 893 and 696, culminating in a total of 3398 being recorded up to 18th March 2013. In the same period this year I have only recorded 374! Why?
Was my effort higher in 2013? No, in 2013 I had seawatched a total of 25 hours 45 minutes up to this date, in 2014 it was up to 40 hours 30 minutes. I then started to think of the other more common species that I record while seawatching, it seemed like it has been a bad year for Brent Geese and Common Scoter (wildfowl in general really) but did the figures match up to what I was thinking?

Looking at the raw numbers does indeed show that it has been a poor year for Brent Geese, Wigeon and indeed wildfowl in general, passing Hemsby. But it also appears at first glance that it hasn’t been a bad year but in fact a better year for Common Scoter than 2013, unlike what I had thought. The table also shows it has been a great year for Gannets and Red-throated Divers (more on the divers later). This, however, does not paint a true picture. As I said before I have been seawatching more in 2014, 14 hours 15 minutes more (57% more) than in 2013 so to get a more accurate picture I decided to look the number of birds per hour.

This table still shows that Brent Goose and Wigeon numbers are far lower than last year as I had thought and that there was in fact very little difference between 2013 and 2014 for Common Scoter and Gannet numbers. Is it due to the mild winter we have had down here? It does highlight the dramatic difference in the two years for Cormorants. It would interesting to know if other areas of the Norfolk coast have suffered similar drops in numbers or the reverse and the cormorants I was recording last year are somewhere further along the coast somewhere?

And so I go onto the Red-throated Divers. Both the above tables suggest that it has been a great year for RTDs so far with over 3000 more recorded and over 64 per hour more than 2013. If I had written this post over the weekend (as I had intended to do) it would have been a different story. On the 17th and 18th March 2014 I had a crazy passage of RTDs, in total over those two mornings (2 ½ hours of seawatching) I recorded 2730 divers mainly going north. So, if I had written this at the weekend the RTD figures would have looked like this:

I could have been writing about all but Gannets being recorded in lower numbers and about how poor seawatching has been this winter but instead I can now rave about the huge numbers of RTDs compared to last year etc but perhaps it just illustrates that you need to catch the right days to seawatch, not go offshore working when the peak days happen etc and that nothing has changed from the two years

Fortunately I’ve put all this seawatch data into BirdTrack so I’m sure if anything can be gleened from this data the real scientists will have a far more scientific and useful approach to analysing it!

If nothing else I have created some colourful graphs to keep Mark happy!

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