Friday, 6 March 2015

those chiffchaffs

 The two interesting Chiffchaffs recently at Ely sewage farm gave me a chance to really get to grips with the vagueries of racial identification of this enigmatic little warbler. One of the birds had slightly worn tips to the wing and tail feathers, while the other one was a much fresher bird, but other than slight differences to the boldness of the primary tip coloration, to all intents and purposes they were identical. When seen with the naked eye it was impossible to tell them apart, and even with a scope it was hard to discern any difference as they flitted through the branches of the railwayside bushes.

           light effects perception.........

My first prolonged view was in dull light,-the worn individual-and this picture on the left is what I was confronted with.However, most of the time I watched the birds in bright light,(above right) and both gave a distinctly different impression. The green tones in the wing were much more obvious- both the primaries and secondaries showed a fresh green edge, and the greater coverts too were green-fringed. Some of the median coverts near the wing bend also showed a green suffusion. Note, however, that the main upperpart coloration remained  greyish-brown, with no green except for a slight olive wash to the rump. The underparts were tinged buff, most strongly on the cheeks and upper flanks, and this stood out more in bright light. In overcast conditions, and when seen against the light, the underparts lost this colour and became more or less white. In fact from a distance in all conditions, the underparts looked white, and the upperparts pale raw umber- all intricasies of tint gone.
Below is a comparison between the tristis types, and one of the  collybita types that were to be seen in the same locality. While superficially similar, notice the shorter and less contrasting supercilium, darker cheeks, and overall greener tint to the upperparts. Yellow appears in the underparts as short streaks, while the overall "buffiness" is more extensive. In some of the photos I took of one of these more "local" birds, the primary projection looked a touch shorter, and the tristis types seemed to show slightly looser and "shaggier" plumage. 


Good points for tristis are the lack of yellow in the face and underparts ( except the underwing coverts), and the lack of green in the mantle and crown, except for a touch of olive on the rump. The tobacco stained ear-coverts, dark bill and legs seemed to fit the bill too, as well as the less tangible features described above, but what was needed was vocal evidence........

chiff chiff chewy chewy chiff chewy chewy chewy...... is this tristis song? Ive never heard it before in the flesh, but from listening to xeno canto recordings, I can't help thinking that the tentative snatches caught on my terrible video sound like a tristis in pre-season practise.( don't expect a bird to magically appear in focus by the way- it won't)