The decision regarding category is often the most complicated part of the work of the Records Committee. Whilst we sometimes struggle with problematic identifications, much more time is spent considering the status of potential additions to the Hong Kong list and upgrades in Category status.
However, I think there are already some rather subtle issues being raised which are worthy of discussion.
Firstly, the question regarding the status of the two flycatchers mentioned by cywong, whilst interesting and of concern for those who saw the birds, is unlikely to affect the position of the two species on the HK list. Both species exhibit a pattern of records typical of a spring passage migrant and the bulk of the records concern individuals with no apparent cage damage.
This is not the case with Red-headed Bunting and Hawfinch. The former has only one record, so the assessment of that individual has a direct bearing on the HK list; if it is deemed to have occurred naturally, or probably so, the HK List (or the categories that most people take seriously, A to D) increases by one species. I believe this to be a highly likely addition to the HK List; however, the bird showed signs of cage damage, and is known to be traded. However, were we to get another in spring or autumn, in excellent condition we would be faced with (another) difficult decision.
Hawfinch is more complicated, with a body of records which show something of a pattern but which includes birds with apparent cage damage. Had the Ping Che bird referred to above not shown cage damage then the species could well have been upgraded from Cat E. Certainly some records of this species do look like they refer to wild birds. However, there is another important point to consider which makes the category assessment process so difficult; that ex-captive birds do not always show obvious cage damage. Such an example would be Bearded Reedling, several of which were trapped at Mai Po a few winters ago and upon examination were in excellent condition; however, being a largely resident species breeding about 1500 km from HK, they were extremely unlikely to have made it to Mai Po naturally.
This leads us on to what cage damage actually looks like. To appreciate this, one first has to understand what natural wear looks like and how moult functions. I don’t propose to go into these in detail here. However, there are one or two important rules that all birders should understand. One rule is that moult is typically symmetrical in that the same feathers in both wings, and on both sides of the tail are replaced at the same time. As such, a bird with a big gap in the primaries on only one wing or with the outer tail feathers missing on one side only is not in moult; this is the result of some sort of damage.
It is also helpful if birders understand the timing of moult, although this varies according to species and is something that has to be slowly learnt (for example most adult buntings have a post breeding moult, except for adult Black- and Red-headed Buntings which moult in winter; hence a worn Black-headed Bunting in autumn is normal, but only if it's an adult). Taking finches as an example, all individuals should be in fresh plumage in early winter as adults moult after breeding and first-winter birds have fledged a few months earlier; limited wear to the outer primaries and tail tips would not normally be apparent until the early spring. Natural wear would affect the plumage of a bird slowly and would not normally be apparent on a typical passerine until the feathers were many months old.
Cage damage affects both feathers and the bare parts (bill and feet/claws). Damaged feathers are eventually replaced (so this only a short term clue) whereas damage to the claws and especially the bill can be permanent (I recall catching a male White-tailed Robin at KFBG years ago which had immaculate plumage and terribly damaged feet and bill, and so it must have escaped sometime prior to being trapped ‘in the wild’).
The base of the bill is often the first place where damage occurs (with abrasions to the base of the upper mandible and loss of forecrown feathering typical) as birds repeatedly poke their heads through the wire of the cage. Other areas susceptible to damage are tail and primaries, with damage ranging from the feather tips being broken to entire feathers being lost. Damage to the body feathers can also occur as birds hit the sides of the cage in panic (this sort of damage is especially unusual in the wild).
Tail feathers are replaced quite quickly (on a short-tailed passerine in about two weeks) so a cage bird might lose part of its tail but subsequently regrow those feathers. However, many passerines have different tail feather shapes according to age. Thus a first-winter thrush will have narrower and more pointed feathers than an adult. On both the Red-headed Bunting and the Ping Che Hawfinch two ages of tail feathers were apparent from the photos, which indicated that at some time in the previous six months (approx) tail feathers had been lost in some sort of an accident.
Ultimately, being able to differentiate between natural moult and wear and damage (whatever the cause) forms an essential part of the assessment process.
Getting back to cywongs two flycatchers, one shows a damaged tail feather and dishevelled plumage, the other is missing a tail. However neither show ‘classic’ cage damage (tips to the tail, primaries and bare parts are in good condition), both occurred at a time of year that fits the known pattern of occurrence, and, as I mentioned above, both species have a history of good records. There are, of course, potentially other reasons why one bird lost its tail (one of the Po Toi cats springs to mind!). As such I would give them both the benefit of the doubt. However, had one been a stunning male Kashmir Flycatcher without a tail, I would be a lot more reluctant to do this!
Please note that these comments are my personal views and not necessarily those of the Records Committee. However, both I and the rest of the RC welcome comments.
[ Last edited by lpaul at 30/06/2009 11:35 ]
