Greyish Willow Warblers

These two individuals were both in sping migration and very distinct among Willow Warblers seen at the time. Birds like these are quite rare in Finland.

31 May 1996 Hanko bird observatory, south coast, Finland.

May 1992 Lågskär Bird Obsevatory, Åland Islands, Finland.

May 1992 Lågskär Bird Obsevatory, Åland Islands, Finland.

Below three photos taken by Hannu Kärkkäinen in Siilinjärvi, central Finland, 22 September 2019. It is an adult bird at the last stages of wing moult. It is normal for adults to look greyer than first-years, but this is somewhat extreme. It is normal that adults are in this stage of moult just at the start of migration, but this individual is late. Most Willow Warblers are left central Finland after mid September. The fact that this bird was moulting seems to be indicating that this is comparatively local breeder, not a straggler from east.

Note also adult type tail feathers, helping in ageing (but in this case ageing is straightforward because the bird is still moulting.

Wing length 68,0. Wing formula 7,5 / 0,5 / 0 / 2,5 / 6,5 / 10 /12,5 / 14 / 16 (note that the wing shape is not final, the outermost primaries are still growing. Outer web emarginations 17,5 / 13,0 / 8,0. Bill to feathering 9,6, hind claw 4,5, tail 47,0, weight 8,7g, fat score 0.


Below some normal spring acredula from Söderskär, Porvoo, Finland Mid-May 2006 and 2007.