Tuesday, September 27, 2011

Dumb tour? mmm...

Another hopeful trip to Portland for that elusive rarity came up trumps this time. Lots of fog at the start and not many birds. A Grasshopper Warbler was all I could muster. Then the excitement. We were all milling around the Obs, I think it was JD who was just about to leave when Prof said "dont go yet John" in a rather serious manner! There was a bird being processed and we knew it was going to be a good one.
It was very quickly pronounced a Blyth's Reed Warbler A. dumetorum

On the tail there is a clear change of shade. I remember some time ago this being mentioned as a good way to age a bird as a first winter.
Whilst growing in the nest, the young bird may suffer food shortages so any available nourishment is re-directed to the most important parts of the bird. The tail will then get whats left, if there is nothing it will stop growing altogether to be resumed when the food supply picks up. The tail quality suffers at this point and shows up as a different shade of colour.
There is another option of an adult loosing its tail completely and during the process of regrowth it suffers the same period of food shortage with the same resultant band.
Thanks Shaun for confirming all this.

Numbering the primaries ascendantly you can see there are emarginations on P3 P4 and P5. (remembering that the outermost P1 cannot be seen as it is so short ). A Reed Warbler would usually only show an emargination on p3 for example.

In the hand the primary projection looked longer than I expected. Measurements later revealed that it was just outside the usual range for Blyth's Reed.
The other thing that seemed slightly unusual was the bill tip colour, the lower mandible of which are usually diffusely tipped dark.