Whilst ringing at Sabkhat Al Fasl in January I trapped a quite grey/brown looking Chiffchaff with few greenish tones. Unfortunately, with Chiffchaffs, things get complicated in the Middle East. With Mountain Chiffchaffs nearby, which look quite like Siberian Chiffchaff tristis, and a series of taxa with intriguing combinations of abietinus or intermediate plumage but tristis-like calls (the brevirostris/caucasicus/menzbieri group), diagnosing Chiffchaffs can be a demanding exercise.
There is only one confirmed record of tristis in Saudi Arabia, a bird I trapped and ringed at the same site in Januray 2014, and the bird give a different impression and appeared much greyer. The bird I trapped seems closer to abietinus or some other integrade.
To make things more complicated apparently many tristis can actually look like this and a recent Dutch DNA study revealed that most abietinus-look-alikes are in fact tristis by DNA. For the time being to identify Siberian Chiffchaff I am only looking at classic tristis (no green tones at all, buff face and flanks) and call like a tristis and unfortunately this bird did not fit properly.