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Case Summary for:
Submission No 245: Black-backed Wagtail Motacilla lugens; Glendale, Newcastle, NSW, 4-10 April 1998. Submitted by R & L Payne and Mike Carter. Verdict: Accepted This record relates a well-publicised record of a wagtail observed by many individuals during its stay in the vicinity of a shopping centre at Glendale, Newcastle, NSW between 4 April 1998 and 10 April 1998. The bird appeared to favour the paved parking areas of the centre, at times seeking refuge on the roof tops of nearby buildings. The bird was partially disabled using only its left leg. An excellent account was provided to the committee describing the bird in detail along with a series of supportive photographs and an analysis of the birds identification. Mike Carter pointed out what he believes (based on extensive research) to be the most diagnostic features of this bird, and in doing so describes how to eliminate the very similar White Wagtail Motacilla alba (race leucopsis). These differences include: (1) a wholly white throat and chin, (2) a greater extent of black on the rump, (3) a more robust bill, (4) the presence of white on the remiges, (5) white basal shaft of the fourth rectrice, (6) mid-grey rather than pale-grey dorsum and (7) the presence of black feathering on the scapulars. It was commented that the combination of these features rule out all other possible wagtails including M.a.leucopsis. It was also suggested that the moderate amount of white in the remiges, the wholly white throat and lack of black on the mantle and back indicate an adult female or a juvenile male (Bird Migration Research Centre 1983; Shigeta 1995 & 1996). And the presence of a yellow on the face may be a feature of some immatures (Wild Bird Society of Japan, 1982). Typical first-summer females have almost no white on the remiges because they retain their juvenile feathers, but individuals with as much white as this bird have been recorded (photo 8, page 8, Bird Migration Research Centre 1983). It was therefore concluded that this individual may have been a first summer female. The committee voted unanimously to accept this record as the third confirmed record of Black-backed Wagtail for Australia. One member commented that Sharpe (1885) reported that some adult non-breeding lugens can have a faint yellow wash on the face. If this is so it is not a reliable way of telling first summer lugens from adults. However, the extent of white on the outer greater coverts (which may be retained from juvenile plumage) and the faded appearance of the dark areas of the remiges does support the first summer age assessment. Proving the sex of the bird though may be more difficult as the wing pattern may fit juvenile male or female (Howell 1990). Howell also said that first alternate males can show a wholly white chin and throat and as little as 15% black on the back (including presumably the scapulars and mantle). It was therefore determined that neither the throat, back or wing pattern could rule out first alternate male conclusively. The committee preferring that this bird be recorded as an unsexed first alternate, probably female.
References and Bibliography
Tony Palliser |