New Cetti's Warbler locality for SNRG

It's not that long ago that Cetti's Warbler was unknown from our part of the world and it was retricted to England's southernmost counties, but in the last 25 years or so, it has spread to almost every region of England and Wales.

Our ringing group's first capture was at Holme Pierrepont (HPP) in 2009. Since then, at that site, we have ringed 86 new Cetti's and had 40 subsequent encounters.

In 2011, we caught our first at Attenborough Nature Reserve (ANR). Here we have since ringed 15 new birds and had 12 subsequent encounters. ANR is approximately 10km southwest of HPP, but crucially it is also in the Trent Valley. Cetti's Warbler dispersal often seems to follow river valleys which provide corridors of suitable habitat. 

 

A map of field records from the National Biodiversity Network atlas clearly shows that the majority of records in our area are along the Trent and Erewash valleys.

 

 

However, birds do occasionally undergo exploratory movements away from the major river valleys and turn up in other interesting places. This is what has happened today, as finally (15 years after the first record at HPP), I caught a Cetti's Warbler at a site near Bestwood.

 

This site is about 13km to the north of both HPP and ANR, but separated by the city of Nottingham. It is, however, connected by the River Leen (a tributary of the Trent). Whether this species has followed the River Leen, or arrived at Bestwood by some other route, can only be guessed.

I've taken the opportunity to look at our Cetti's data in a bit more detail. As can be seen from the chart, we ring more males than females. Out of 101 new Cetti's ringed, 63 were male, 33 female and 5 unsexed.

 

And the following charts show that there is very little variation in wing length or weight.

 

 

And the averages are as follows:

Mick P.