Grey-headed Lapwing (Vanellus cinereus) breeds
between 32 and 40°N in Japan and southern China
and migrates southwestwards to winter in the
tropics. Like many of the Vanellus plovers it
is a powerful migrant and vagrants have been
recorded to Sulawesi and Borneo.
The theory of reverse migration as an explanation
of vagrancy for long-distance migrants requires
that one of the directional vectors of normal
migration is reversed. Thus a Grey-headed
Lapwing that departs from a paddyfield in
northern Thailand to the southeast instead of
northeast and continues until it finds suitable
habitat at 30°S (instead of north) reaches
northern NSW. The area around Burren Junction
(Namoi Valley) is decidedly swampy after heavy
rainfall in early June. The compelling feature
of this explanation is that it requires only a
single low probability event.
The Northern Lapwing (Vanellus vanellus) is a
regular trans-Atlantic vagrant from Eurasia to
the eastern seaboard of the Americas, providing
an example of long distance vagrancy against the
prevailing wind.
PJ MIlburn
--
The Milburns
42 Bundey Street
Higgins
ACT 2615
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