Subspecies

[ledzep]

As I have been working with my birding app and the new AviList, I have also been looking at the logging of subspecies. I know it is possible to log more than one subspecies of a bird at the same time in the same location, but I'm wondering how often this happens? When I google, there are some cases in North America of subspecies overlap (eg Yellow-rumped Warbler) but I wonder how often this happens in NZ. One example I can think of is the Red Knot, where you could look at a flock and be seeing rogersi and piersmi at the same time (and perhaps be able to tell them apart if breeding plumage is still present). You could see North Island and South Island Saddleback on the same day, but in different locations (Zealandia and Moturua Island). Perhaps the Tasmanian subspecies of Shy/White-capped Albatross amongst the steadi. Interested in any comments or examples of where this occurs - where you would be logging two different subspecies of the same species of bird at the same time at the same location. I think it is possible, but quite an unusual situation.

[Oscar Thomas]

Hi Duncan, interesting idea. A few points off the top of my head:
- The tīeke/saddlebacks are regarded as separate species by all authorities.
- The shy/white-capped albatross status is contentious, but current research also indicates they can't be reliably identified in the field (Tennyson 2020) https://www.birdsnz.org.nz/wp-content/u ... 1__333.pdf
- It could happen with little shags, but the Australian subspecies is considered indistinguishable from the pied morph of the NZ subspecies. Similar story with grey duck and red-billed gull. Vagrant little shags to the subantarctic were considered to be from Australia as they were all pied morphs: https://www.birdsnz.org.nz/society-publ ... ittle-Shag
- It has happened with New Zealand dotterel, when a pukunui went to Shoal Bay and joined tūturiwhatu (Dowding 2020) https://www.birdsnz.org.nz/wp-content/u ... 29-731.pdf
- Little penguin/kororā taxonomy is messy but I have seen white-flippered penguins in Otago Harbour which in theory are the NZ/Canterbury type rather than the Australia/Otago type.
- Are black fantails/pīwakawaka seen in the North Island vagrant South Island fantails or black North Island fantails?
- It is not uncommon to see Gibson's and Antipodean albatross side by side at sea which most regard as subspecies, same with Snares and Antarctic cape petrels.
- Subspecies can be hard to ID with certainty but other seabirds I believe I have seen at once include standard and subantarctic fairy prions, northern and southern Buller's albatross. A lot of observers on eBird etc. identify subspecies based on range; but if a vagrant sacred kingfisher, black-backed gull, black shag, marsh crake etc. flew to NZ we would be none the wiser.

[Brendan T]

To latch onto your albatross comment, the other that immediately springs to mind is D. a. gibsoni and D. a. antipodensis, and depending on which taxonomy you follow, T. impavida and T. melanophris. There'd be quite a few seabirds where you'd have a similar situation. I've been on a boat off Terrigal, NSW, where wiser birders than I have said we've had steadi and cauta based off the seasonality of the plumage.

It's my understanding there have also been Bar-tailed Godwits others than L. l. baueri recorded in NZ?

Outside of New Zealand, my mind instantly went to Striated Pardalotes in Aus, as well as Shining-bronze/Shining Cuckoos, which both have seasonal overlap along the east coast. While C. l. lucidus is a regular winter visitor to Aus, I'd be curious to know if C. l. plagosus has ever been recorded in NZ.

Edit: Ninja'd by Oscar, and a really great point he makes in his last paragraph. I wonder how many times this overlap has occurred and no-one has ever known. Though not a subspecies, I'm always checking the SIPO flocks here in hopes of an Australian Pied Oystercatcher, as we Aussies would always get very excited whenever this single, star SIPO showed up at Old Bar, NSW. The reverse seems less likely, but you never know.

[Nick Allen]

Seabirds are probably likely to cause the most multiple subspecies lists.

I dunno, adding subspecies might cause more confusion with observers trying to assign what they see to a subspecies when this is pretty much impossible in the field (as with White-capped Albatross). It certainly caused a few issues when I was reviewing eBird.

Little Tern (sinensis and placens) - usually separated temporally and placens is probably just a vagrant
Little Penguin (minor and novaehollandiae) - also hybridises - difficult to tell apart in field, probably impossible
Antipodean Albatross (antipodensis and gibsoni)
Buller's Albatross (bulleri and platei)
White-faced Storm Petrel (maoriana and dulciae) (and albiclunis depending on which taxonomy you are using)
Cape Petrel (australe and capense)
Fairy Prion (turtur and eatoni) - and other prions as the various taxonomies don't always agree
Fulmar Prion (crassirostris and flemingi) - theoretically
Wedge-tailed Shearwater (pacifica and chlororhyncha)
Little Shearwater (assimilis, kermadecencis, and haurakiensis)
Common Diving Petrel (urinatrix, chathamensis and exsul) - probably separated geographically, but almost certainly impossible to tell apart in field
South Georgia Diving Petrel (georgicus and whenuahouensis) - georgicus is probably a vagrant
Little Shag (melanoleucos and brevirostris) - there are questions that the Aussie race is regular in NZ or a vagrant
Stewart Island Shag (chalconotus and stewarti) - supposed to be separated geographically, but is that known for certain
Kaka (septentrionalis and meridionalis) - from memory the 2 races have crossed Cook Strait, but the subspecies status is debated.

Quite a few passerines have multiple races, each on different islands that could be seen in the same day.

Avilist has the two saddlebacks as separate species.

[ledzep]

Thanks, some good comments. I've seen the Great Egret in 12 countries and decided that I've seen all 4 subspecies (alba, melanorhynchos, egretta and modesta) but my decision purely based on range. I wouldn't know how to distinguish them in the field. So if a vagrant Australian shag or Kingfisher turned up in NZ its unlikely I'd be able to tell it from the local ones. Albatrosses and petrels could be likely candidates, and BT Godwit. I was never sure with the white-flippered penguins. Good point with the black fantails in Wellington - I've never seen one but if I did, how would I know if it was a NI or SI vagrant? Probably more scope in Australia, especially with the cuckoos you noted.

If we do see a bird in NZ that is out of the ordinary, it could be an Australian vagrant subspecies, or a hybrid. Get's tricky sometimes.

[Michael Szabo]

This 2021 paper indicates there may be multiple subspecies or even species of Rifleman across both main islands:
https://onlinelibrary.wiley.com/doi/ful ... /ece3.7358

[SomesBirder]

I suspect that it is possible for the mainland Korimako to reach the ranges of at least one of either the Three Kings Korimako or Poor Knights Korimako. This will becoming increasingly likely if the mainland Korimako population recovers in the northern North Island. I don't know how to tell the subspecies apart, however.

[Jan]

This raises the perennial question of 'what is a species' anyway. It's only a human construct that we have put on other living things that share the same planet as us. The lumping and splitting conundrum has been around for a long time too. Most likely there are subtle differences in humans that could be described as subspecies, but we don't want to recognise that?

[Michael Szabo]

There are no recognised subspecies of Homo sapiens. The scientific classification for modern humans is Homo sapiens sapiens. The genetic diversity within the entire human population is less than that of some other ape subspecies and the concept of dividing living humans into subspecies is scientifically invalid.

[ledzep]

The Rifleman paper was interesting. I did some research on the 4 subspecies of the Great Egret. From what I read, it would be possible to tell them apart in breeding plumage, but in non-breeding plumage there doesn't seem to be much different other than size, which would be very hard to be sure of in the field. So if we had a vagrant from America or Europe turn up here in NZ in winter it would be really hard to be sure until the breeding plumage reappeared. Same for the Red Knot, I'm not sure how I could tell apart rogersi and piersmai in non-breeding plumage. Fortunately they often arrive or depart with some colour and I've seen some which are much darker red on the belly than others.

Thanks for all the comments, I think the consensus is that subspecies can overlap in unusual but not improbably circumstances, and it is possible to log two different subspecies of the same species at the same location on the same day. (Is three subspecies ever a possibility?).