Stejneger's Petrel v. Swinhoe's Storm-Petrel (1 Viewer)

I have just been looking at my Japanese field-guide and I cannot find any convincing way of telling Stejneger's Petrel (O. longirostris /tristrami) and Swinhoe's Storm-Petrel (O. monorhis) apart - and my copy of Harrison is back in Europe. And is longirostris really = tristrami?

OK, so Stejneger's is the bigger of the two but is that of use in the field? I'm planning a ferry trip up the coast to Hokkaido and I want to get this issue sorted before going. Any suggestions would be gratefully accepted.

:hippy:

Hello Hapax!

I think you are getting confused between:-

Stejneger's Petrel, Pterodroma longirostris, which is a gadfly petrel and doesn't look anything like a storm petrel

and

Tristram's Storm Petrel, Oceanodroma tristrami

unfortunately i have no idea how this species looks, so may be very difficult to separate from Swinhoe's.....

Thank you very much for that. Then it's my field guide (Japanese Soc. for the Preservation of Birds 2002, in Japanese) that is totally confused... It definitely has Stejneger's Storm-Petrel (sic) (Oceanodroma tristrami) and Swinhoe's (Oceanodroma monorhis) - well, there's a turn-up for the books as they say. So the field-guide should say Tristram's Storm-Petrel (O.tristrami) - logically enough.

To sum up: it should be Stejneger's Pterodroma longirostris, Tristram's Oceanodroma tristrami and Swinhoe's O. monorhis, with the i.d. confusion being between the last two... good thing I didn't bring Matsudaira's Storm-Petrel O. matsudairae into it.... Wilson's, Madeiran and Leach's are all on the Japanese list as well.

hmmm...tricky! :hippy:

There does seem to be some confusion over the names.

There are three commoner small-medium sized dark petrels in Japanese waters.

The first is Swinhoes Storm Petrel - Oceanodroma monorhis

The second is Tristram's Storm Petrel - Oceanodroma tristramii

The third is Matsuidaira's Storm Petrel - Oceanodroma matsudairae

The third species breeds only off the Ogasawaras islands and rarely wanders into closer inshore waters. It can be told from Tristrams's by the white flashes on the primaries and lack of a dark rump. It is around 25cm long and has a wingspan of 56cm.

The second species Tristram's breeds largely off the Izu islands, Ogaswaras and Haiwaiian islands. It iis the smae size as matsudaira's, but in contrast has a pale rump fawn rump and larger pale areas on the secondary coverts reachng the lesser primary coverts/alula and the tertials (the pale area just reahes the tertials on Matsudair's). It has similar flight patterns to Matsudaira's, being rather stiff-winged and gliding for long distances similar to shearwaters and Bulwer's Petrel, rarely if ever hovering over the water.

The first species Swinhoe's is a smaller darker brown bird, with no discernable pale rump, and much smaller paler areas on the secondary coverts only. It also has a less forked and shorter tail than the other two, Matsudaira's being the most forked, and Tristram's somewhere in between. Swinhoe's also tends to be more fluttery and glide for shorter distances than the other two longer-winged species, being only 19cm in length and having a winspan of only 46cm. This species is found mainly in the Sea of Japan and breeds as far north as Vladivostock, but there are other records from the Pacific coast, maily from islands off the north of Honshu, with breeding also recorded on the Izu islands, and I have also seen two birds in the outskirts of Tokyo Bay in April.

Swinoe's, at least in the Sea of Japan is meant to be a later migrant, not arriving until the latter half of May, and departing in September, though (perhaps lingering longer in the Pacific and arriving earlier too..though this is unproven at present), while Tristram's is a winter breeder, being most common from November to June before dispersing more widely and Matsudaira's breeds from December to June before dispersing.

Of course any dark-rumped species of storm-petrel has to be seen well to be totally sure of ID.

Least Storm Petrel has also been recorded in Japanese waters at least once and several unknown birds have been seen in Korean and Japanese waters of a potentially new species perhaps?

For more discussion on this difficult group see the following discussion on Kantorilode:

http://ca.geocities.com/kantorilode/Species/Dark-rumpedStorm-Petrels.html#Dark-rumped Storm-Petrels

Sean
Hiroshima

I forgot to mention that some Leache's Petel can also be dark-rumped and could perhaps be misidentified as Swinhoe's, though they have a deeper forked tail and are slightly bulkier.

Excellent information! Just what I wanted - thank you for that, sean! It seems like quite a few people have had trouble with this difficult group in Japan. I'm sending a note to the editors of my field-guide to let them know of their little error.

I was interested how the reliability of single reports gets taken for granted - as Nick Lethaby commented in the linked article, a report by Alstrom and Olsson of "200 Swinhoe's" from the Kushiro ferry gets included in Brazil's guide, and from then on any dark-rumped petrels seen from that ferry might tend to get put down as Swinhoe's ("must be Swinhoe's") without any real i.d. basis.

I also liked the story of Fergus Crystal in the ornithological museum in Taiwan telling the curators that their supposed Swinhoe's specimen was in fact the first Taiwan record of Tristram's.

It is also apparent that there's a lot of room for proper ornithological work in this area - for example, searching for breeding sites on offshore islets or in the mountainous areas of larger islands; or clarifying the issue of the very small, all-dark storm petrels mentioned by some observers. It also seems as if hardly anyone makes it beyond Hahajima in the Ogasawaras - presumably the idea is to see whatever turns up from the boat, then tick off the Bonin Is. Honeyeater on Hahajima and head back. A pelagic from Haha-jima to Iwo-jima might be very interesting.

:hippy:

Hello again Hapax,
it seems I was too fast in my original response.
Stejneger's Storm-petrel is an alternative name for O.tristrami, but it is of course a different species from Stejneger's Petrel, P.longirostris.

Probably the name Stejneger's for O.tristrami should not be used to avoid confusion therefore!!

good luck with your sightings,

James

Dear Hapax

Glad the information was of use.

Yes, single observer records ...even multiple observer records are often difficult to assess, as very few people get to see these species really close enough and in the right kind of conditions to ID them.

I don't think Mark took that record for granted. the Alstrom/Olsonn record. I think as the observers had prior experience of tha species, he gave them the benefit of the doubt, though of course caution needs to be exercised as Tristram's is far commoner than Swinhoe's in the Pacific.

However, contrary to what Nick believed, the status of Swinhoe's is far from clear. Yoshiki Watabe confirmed there is or was a couple of small breeding populations of Swinhoe's on the Pacific side of Japan, and it is possible that birds from further north, especially in the large colony in Vladivostock could return later at a more leisurely pace and still be around in October or November, as could dark-rumped Leache's, while Tristram's wintering quarters are not known precisely, but they are rarely seen after June from the ferries running up the Pacific side of Japan.

Of course as Nick said, caution is always advised when identifying these small dark petrels, and Mike Yough and I had discussed the finer points of ID and what would be likely before he went on his trip to Hachijojima and he freely admitted that many birds went unidentified.

Although I haven't birded with them I know Nick and Fergus are excellent field observers and are meticulous when it comes to any kind of ID challenge. I wish I was so thorough. I usually do a lot of research on seabirds before I do a trip and bone up on what might be likely to occur, the various ID problems of similar species etc. However, out in the field, it often comes down to 'instinct' in the end..as you don't have all the facts to hand.

There is according to a friend of mine, Neil Davidson a Japanese trip from Tokyo to the Ogasawaras..taking in the Izu islands en route, but not sure if it stops off at Iwo-jima.

I believe a pelagic from New Zealand did this spring, but as you say most boats don't venture that far and indeed most seawatching is done from ferries, which with their increasig speed and often non-birder friendly schedules are not the best for such birding.

It would be great if regular pelagics could be set up from Tokyo, Sendai, Nagoya or Osaka, as well as Tomakomai and Kushiro...alas there is not the interest at present.

There has been extensive surveying of most offshore islands in Japanese waters in the past, but of course seabird numbers fluctuate...and as most petrels are nocturnal they are difficult to assess. Moreover, there are literally thousands of islands and I am sure many of the very small inaccessible or uninhabited ones have not been surveyed at all.

As to research..great idea and some research is being done for example the Short-tailed Albatross and Japanese Murrelet. However, it seems unless it is an endangered species and a well-known one at that there is little grant money out there for that kind of research. Most of the grant money goes to big projects like the Crested Ibis and Oriental White Stork programs.

Perhaps if more money was made available from foreign institutes and research organisations, it might encourage the Japanese Governemnt to do a little more in terms of research and conservation of less well-known species and indeed take nature conservation more seriously in general. However, at the moment the Environmental Agency is nothing more than a rubber stamp for other Governement Departments economic development..hence all the largely unnecessary dam and road construction projects...so there is little governement money available for any such surveying projects.

Radio-tagging would be an excellent way to lay to rest unanswered questions of seabird migration routes and feeding patterns..now the technology is there ,we just need the money.

Actually a new pocket guide has been brought out in Japan on seabirds, which has some excellent illustrations, but the text is unfortunately (for Non-Japanese) all in Japanese.

There is a growing interest in seabirds, but most birdwatchers in Japan still give them a wide-berth as they are so difficut to ID and require a lot of time, money and effort in the 'field' for seemingly little reward. The new ID guide and two new NE Asia fieldguides in English wil hopefully go along way towards helping improve general observer knowledge of the subtle differences between Swinhoe's and Tristram's, though alas it seems, not dark-rumped Leaches stormies.

There are several disputed islands or inaccessible islands in Japanese/Korean/Chinese waters that could conceivably hold small populations of an as yet undiscovered small dark petrel, or subspecies of Swinhoe's or dark-rumped Leaches might be breeding in small numbers..we will just have to wait and see.

Regards

Sean

lostinjapan said:

Dear Hapax

I believe a pelagic from New Zealand did this spring, but as you say most boats don't venture that far and indeed most seawatching is done from ferries, which with their increasig speed and often non-birder friendly schedules are not the best for such birding.

Regards

Sean

Click to expand...

In case of interest, here's a report I saw recently from the New Zealand to Japan pelagic you refer to:

http://home.btconnect.com/wildwings/wpotriprpt.html

and also one for the gripping bi-anual trip from Yokohama to Torishima, next sailing in 2008 I think

http://www.club300.se/Files/TravelReports/Japan0603-BA.pdf

not cheap, but they did see over 500 S-t A...which must have been nice.

Hey Ed

Wasn't till I revisited this thread, that I notived your excellent links.

Cheers

Sean