I have never really liked Australian Magpies; ugly things, apt to make
unpleasant begging screams when they are young and to dive-bomb birdwatchers
when they grow up. For some reason though, Ken Rogers and I actually looked
at one in April, about a km from our house in Nink?s Rd (about 70 km n.n.e.
of Melbourne, surrounded by Kinglake National Park). To our surprise, it was
a Black-backed Magpie, rather than the White-backed form we expect and are
accustomed to in this part of the world.
Interested, we dug out Burton & Martin?s paper on hybridisation of
Black-backed and White-backed Magpies in South-eastern Australia (1976; Emu
76: 30?36). In short, this paper described the hybrid zone between the two
as being fairly broad in Victoria, with White-backed occurring to the south
of the Great Dividing range, Black-backed to the north, and hybrids in a
broad band (roughly 200-250 km wide) on the inland slopes. The southern
limit of the hybrid zone ran roughly through Ararat and Maryborough in
western Vic. to Mansfield in the E., but dipped slightly in central Vic.,
extending s. to Wallan due north of Melbourne and just e. of Melbourne, as
far south as Healesville. This put our bird on the very fringes of or just
outside the hybrid range, where we should not be seeing full-on Black-backed
Magpies, but White-backed Magpies or rather White-backed-like hybrids.
Amongst other things, Burton & Martin presented a hybrid index allowing
dorsal pattern to be scored. Pure White-backed Magpies are given the score 0
and have a wholly white nape, mantle back and runp (with some grey grunging
in females and juveniles); pure Black-backed Magpies are given the score 5
and have a jet-black mantle and back; intermediates have scores of 1 (some
black markings on the mantle, about level with bend of closed wing), 2
(narrow, sometimes incomplete black band across upper mantle), 3 (broad
black band across mantle) or 4 (almost full-on black-backed but black
doesn?t extend onto lowermost back).
Thus informed, we have started looking a little more closely at the Magpies
in the valley where we live. We reckon we have a population of about 20
magpies, all hanging around fairly small discrete territories along the
narrow strip of patsure on the valley floor; the thickly forested slopes of
the valley are not used much by Magpies. Most of our magpies are Stage 0
White-backeds, but we have several interesting birds, each of which has its
own ?patch? upon which it is readily found: (1) The stage 5 adult female
Black-backed that we first saw; (2) a stage 4 adult male hybrid; (3) a stage
2 juvenile hybrid; (4) a stage 3 adult male hybrid. These individuals are
all readily distinguished from one another on plumage characters, and
interestingly, they live on adjacent territories, all occurring within about
800 m of one another (the valley is about 3 km long); the female
Black-backed is usually seen with an adult male White-backed. Exactly when
these individuals arrived in our area is unknown; it is quite possible that
they have been here for years but avoided our attention by pretending to be
so boring that we didn?t look at them.
This is probably no more than a pleasing local oddity, but the other day
when driving to RAOU headquarters, I saw a stage 2 adult male by the
roadside in Wattle Park. It made me wonder (on the basis of the huge sample
of 4 out-of-range hybrids and 1 out-of-range Black-backed) whether the
distribution of Black-backed Magpies could have changed since Burton &
Martin did their study in the mid-seventies. Could Black-backeds be moving
south? Or have they always occurred this far south in small numbers? Any
comments, anyone?
Danny Rogers
340 Nink?s Rd
St Andrews
Victoria 3761.
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