Ageing Leach's Storm Petrel

Every time I get to see one of those blackish, passerine sized seabirds during gale force winds, my heart misses a beat or two. I just can't grasp how such a small bird conquers the elements with such ease.

But for a Dutch guy it's rather unusual to have a truly decent look at a Leach's Storm Petrel. Basically we only see them in the unfavourable conditions of a heavy autumn storm, when they pass by at quite a distance, in the mean time disappearing behind the waves half of the time. Spectacular, but it doesn't allow any plumage studies!

But for the first time in my life I had a more than close inspection. The lovely people at bird hospital De Wulp (The Hague) always inform me when they have an unusual bird inside. Unfortunately this Leach's died over night. But being dead and all, I did have the opportunity to examine the corpse.

Was I able to age it? Based on Baker (2016) and Demongin (2016) it's a 1st cy. Furthermore, this very nice BB article can be found online.

The blackish primaries and secondaries were all of the same generation and rather fresh. Note how pointed the outer primary is. In adults they should be worn and bleached in autumn, there should be some moult visible in October and the outer primaries should be more rounded.

There are several other clues...

...like the colour (grey instead of brownish) of the greater coverts. Several even have white edges.

Perhaps most striking are the white edges on the tertials.

The buffy spots on the inner webs of the primary coverts were very striking, too. I had no idea Leach's had these spots! I have no clue whether it's age related, or not (if you do know, please let me know).

It was an unexpected feature that I think is nice to share.

What a shame this little gem died, I would have loved to put a ring on it and send it to the southern hemisphere to winter!

#ageing #LeachsStormPetrel