Some of the science

On our visits we try and add value to everything we do. Sometimes this can be simple things like measuring and weighing birds - proxies for fitness and condition - whilst other things can start out simple but become more difficult.
One thing we thought we had mastered from last year was determining the sex of individual birds. This year we felt we had to start all over again.

The top shows what we consider to be a male, and the bottom image a female. It all has to do with the presence and extent of white under the wing. The top image shows white all across the wing with definite fringing on the primary coverts. The bottom image still has the patch of white feathers close to the body, but is lacking the extensive white fringing.

Fine you might think, but consider the next two:

Male or female?

We decided 'this' needs more work - the reference texts didn't help much either. So, next year we intend to take more photographs and remove selected feathers for definitive sexing analysis via DNA  so we can produce guidelines for ourselves and others with regards to sexing Storm Petrels. 

Ageing them is another thing altogether.....