Sorry for a late weigh-in on this thread. It is an extremely interesting thread. Here is a warning that this post is long and technical. I agree whole-heartedly with Jeff Davies’s and Kevin Bartram’s posts that the Hamilton bird is a leucopsis form of Ninox from Tasmania, based on the features they outlined. Last year there was an offline discussion about the Ninox novaeseelandiae/boobook complex, the split of Morepork, the status of the “red boobook’ in the NQ rainforests, etc. I went to the Australian Museum (AM) in Sydney with Murray Lord to look at skins of small Ninox owls from Tasmania (leucopsis), mainland (boobook and ocellata), the Wet Tropics (lurida), Lord Howe Island (albaria) Norfolk Island (undulata) and New Zealand (novaeseelandiae). This is a complex group and the AM collection does not hold the whole story. However, I got some insights and generated some hypotheses to share. Murry posted his photos of selected specimens on-line, and you can see that the Gabo Island bird looks like the Tas birds. I don’t have my notebook (in storage) but the measurements fitted Tasmanian birds perfectly and it was too small to be a mainland bird. There were 2-3 other specimens from Sydney in the AM (all >80 yrs old) that also fit Tasmanian leucopsis on plumage and measurements. I am convinced that Tasmanian leucopsis sometimes migrate to the mainland. However, there are many winter records of boobooks from Tas, so it is not a total exodus. I even saw one in my yard in Hobart in the winter of 1988. Tasmanian leucopsis very closely matches NZ novaeseelandiae in plumage and measurements. The functionally extinct Norfolk Island subspecies undulata very closely matches both Tas leucopsis and NZ novaeseelandiae. These three forms comprise a tight group that seemingly differs significantly from mainland Aus boobook and ocellata on plumage and measurements (by ‘significantly’ I mean the variation within each group is obviously less than the variation between the two groups). It is not a matter of degree, but a clear division, with no intermediates blurring the distinction. Whether there is any point in recognising ocellata as a distinct subspecies from boobook, I am unconvinced (there is continual variation across the continent with no obvious place to draw a line; however, I have not delved into this in detail). The extinct Lord Howe I form albaria is a little different from all the others, but is most like Australian boobok/ocellata. It certainly does not look to be part of the novaeseelandiae group. It seems that Schodde & Mason (1997: Zool Cat Aus 37.2) made a mistake by placing albaria as a subspecies of Morepork N. novaeseelandiae. Some people advocate that there is insufficient evidence to prove the trans-Bass Strait migration. However, I see no reason why they wouldn’t cross Bass Strait, it is hardly a shocking notion. I don’t believe that presence of leucopsis-like skins from the mainland can be adequately explained by postulating variation within mainland boobooks that has been overlooked. Besides, the evidence is difficult to deny. The eminent museum ornithologist Gerlof Mees (1964, Zool Verh. 65:1-62) recognised 7 specimens of Tas leucopsis from Vic and 1 from NSW (all in winter), while McAllan & Bruce (1988 The Birds of NSW: A Working List) listed 3 more from NSW. There have been several more in Vic since then. Evidence of birds in migration are 3 specimens from Bass Strait (1 on On King I, 1 on Flinders I. and 1 at sea of the Hunter Is. (Mees 1964), 1 at sea off Gabo I., Vic (in the AM) and a bird seen in a cave on Albatross Island, Bass Strait, for a few days in Sep 1984 (Brothers & Davis 1985, Tas Bird Rep 14). However, a much more interesting question is why would there be a change of form across Bass Strait, rather than across the Tasman Sea (i.e. why does leucopsis fit morphologically with novaeseelandiae instead of with boobook)? How might this scenario have evolved? Firstly, consider that the Tasman Sea has existed for over 50 million years and Bass Strait has existed for under 20 thousand years. The ancestral owls didn’t invade Australia and then evolve into a different species on NZ, Norfolk and Tas. There must have been a double invasion. Perhaps the first invasion saw ancestors of the novaeseelandiae group distributed throughout Australia and NZ, but a second invasion saw them displaced on the Aus mainland by ancestors of the boobook group. Alternatively, perhaps novaeseelandiae and boobook diverged into two species either side of the Tasman Sea and then the ancestors of leucopsis reinvaded from New Zealand to displace boobook in Tas (and the ancestors of undulata colonised Norfolk Island from NZ). It could be that leucopsis is closely related to boobook but resembles novaeseelandiae due to similar environmental demands (convergent evolution). This could be tested genetically, but my feeling is that this is not a case of convergence but s case of divergence. Perhaps there are other explanations, but not that leucopsis diverged from boobook when they were separated by the appearance of Bass Strait. I know of no other scenario where a Tasmanian animal or plant is more closely related to a NZ one than to a mainland one. With all respect to Kevin, I do not see any parallel between Ninox owls and other candidate bird splits across Bass Strait. I don’t mean there are no potential splits, but they are not the same. (I’ll get to fantails soon, but first to Red Boobooks). The NQ form lurida (the ‘rainforest boobook’ or ‘red boobook’) in the Wet Tropics is really intriguing. The breeding range of lurida is entirely encircled by the breeding range of the non-rainforest form the ‘boobook and/or ocellata’ (b-o) and the two morphologically distinct with no overlap. Lurida has been muted as a separate species on several occasions. I have seen what I believe to be hybrids between lurida and b-o either side of Paluma and possibly somewhere around the Atherton Tablelands. Jeff Davies is not convinced, and perhaps he is correct that they are just pure b-o at the darker end of the scale. Either way, these potential intermediates are rare. If there are no hybrids between lurida and b-o then lurida is clearly a good species by any definition. However, even if there are a few hybrids but no general cline or jumble of intermediates then they also must be different species. With few exceptions, it is technically not possible to have sympatric subspecies with sharp boundaries in animals, because subspecies are, by definition capable of hybridising when they are in contact. Hybridisation will lead to a large number of intermediates and eventually a cline. The lurida has such a tiny range with such a big border abutting b-o that the intermediates would be more common than pure lurida, which is not the case. It might be argued that the habitat difference keeps them separate and prevents hybridisation, but I think this is incorrect because they would still hybridise extensively at the margins of the rainforest unless they were reproductively isolated (which would make them different species by any definition). It follows that lurida did not evolve in situ in the Wet Tropics but is a remnant that has been displaced by b-o from most of its range but has held on in the Wet Tropics rainforest. Perhaps lurida is related to novaeseelandiae and leucopsis, but the morphological evidence for this is not striking. I can’t think of another pair of birds like this in the Wet Tropics or anywhere else in Australia. These are hypotheses generated by morphological data (plumages and measurements) to account for distributions of taxa in an evolutionary framework. They could be tested by molecular studies or field work or potentially other ways, but they have not been. I stress that they are just hypotheses and my data are fairly cursory. Thanks to Murray Lord, Jeff Davies and Martin Cachard for stimulating conversations on this topic. Kev Lobotomi suggested that ‘grey’ fantails are a similar taxonomic scenario to the Ninox complex with dark forms in NZ, Tas and NQ. I see some similarities but I think they may be fundamentally different evolutionary scenarios. I’ve not looked at specimens of fantails so I am just theorising. The unusual thing about the Ninox owls is that the break between the two groups is Bass Strait. The Tasmanian birds sit with the NZ birds. The Tasmanian Grey Fantails (alisteri) are darker than the mainland ones (albiscapa) with slightly darker tails, but the differences are not huge. The New Zealand Fantail (fuliginosa) is very different to alisteri and albiscapa. Fuliginosa has a black morph (which is virtually all black) and a so-called pied morph. The pied morph is very orange below and warm brown above with all but the central pair of tail feathers almost entirely white; the juveniles are extensively scaled rufous; the tail looks in the field to be bigger and is fanned even more than in Aus birds, if that is possible. (Be nice to know if measurements support the bigger tail, but I don’t have that vol of HANZAB). Thus the break between the two groups of fantails seems to be the Tasman Sea rather than Bass Strait. This means that a double invasion scenario is not necessary. The simplest hypothesis is that ancestors of fuliginosa crossed the Tasman Sea from Australia to colonise NZ sometime in the last X million years (not too far back). Much more recently (<20 thousand years), the formation of Bass Strait created a gap in the range of Grey Fantails in Australia and alisteri and albiscapa began to diverge. The sea barrier means that their breeding ranges do not abut so there is no longer any significant hybridisation between them. How long this needs to go on for until they become different species is a difficult question (how long is a piece of string?) Alisteri is not a remnant but part of a diverging pair. By contrast I think that Ninox n. leucopsis is a remnant in Tasmania. The form of Grey Fantail in the Wet Tropics (keasti) is very dark and quite distinctive. It is the only form of Grey Fantail that breeds in NQ. Albiscapa occurs as a winter migrant but since it doesn’t breed in NQ there is no chance of hybridisation. It may be that keasti has diverged into a separate species from albiscapa (another question about string), or it may even a remnant that evolved from a different origin to albiscapa. The Ninox owls in NQ differ because the breeding range of one (boobook and/or ocellata) completely encircles the breeding range of the other (lurida). Like Kev, I look forward to feedback. Cheers, David James Sydney ============================== =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au
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