Some largely bibliographical musings on the history of Iberian Chiffchaff on my blog at
http://birdingcadizprovince.weebly....ge/a-mysterious-mosquitero-iberian-chiffchaff Interesting to note how much notice was taken in popular guides of tristris whilst ibericus/brehmii was largely ignored - ironic as the former is still classed as a race of Common by most authorities
It is particularly pleasing to highlight the largely forgotten role of Captain Hubert Lynes, who studied them near Gibraltar (The Ibis Vol II 1914 – see
http://www.biodiversitylibrary.org/item/100092#page/370/mode/1up), in realising the birds were Chiffchaff rather than Willow Warbler. Like those before him Lynes initially mistook the Iberian Chiffchaff's tripartite song as a local dialect, not of Chiffchaff but Willow Warbler but, unlike others, he carefully investigated the situation. On finding a nest and collecting a specimen he realised he'd made an error and that the birds were a kind of chiffchaff. It's worth quoting Lynes' perceptive note more fully: “The only other breeding Phylloscopus (so far as we could find), was by its song, I think anyone would have agreed, a Willow-Warbler; singing males of this species shared the cork-oak glades in about equal proportion as Bonelli's. For a Willow-Warbler, true, the song was unmelodious and disjointed (“tin-potty”, if one may use such an expression), the first two notes jerked out, so that for a moment they might have been put down to an eccentric Chiffchaff, had they not invariably been followed by the four or five notes in descending scale characteristic of the Willow Warbler – in short, if it was a poor Willow-Warbler's song, it was an impossible Chiffchaff's”.*He went on to relate how found a nest and eggs (which more resembled that of a Chiffchaff than a Willow Warbler) and shot the female. On examining the latter and a further six specimens he collected, he found that “with no little surprise” it possessed “all the external characters, dimensions, wing formula, emargination, etc of the typical Chiffchaff” and, although he noted the plumage was largely the same as British birds he observed that “the sulphur yellow axillaries may be a trifle brighter.” Lynes went on to note that, unlike the plumage, “the peculiarity of the song, which is constant, must have some significance” and then discussed whether the birds were resident in the area (as widely assumed) or were, in fact, migrants. Lynes was a very acute observer not afraid of tackling the Cisticolas (one of which is named after him) on which he wrote a groundbreaking paper (all the more impressive given his service in the navy left him 'gun-deaf').