ML362536771

Age

Not specified

Sex

Not specified

Observation details

1 bulweria type bird observed at around 6.20 am for 5 minutes, flying with the ship southward in traveling mode. First impression was that of a larger bird, and first thought was a dark morph Wedge-tailed Shearwater due to the longish tail, the uniform brownish plumage under and above without any contrasting pattern, and the rather relaxed, buoyant flight style, with very few wingbeats if any, lacking the jerky or snappy moves of smaller petrels. The bird was alternating sequences of up and down wheeling, at times reaching fairly high on the top side, and low smooth glides on slightly arched wings , while following a general southward direction at about the same speed as the ferry (25 kts). With nearby Streaked Shearwaters providing size comparison it became clear the bird was too small for a Wedge-tailed and with the distance (it was a good 100m away) and looking through a mirrorless camera i couldn't get a sense of what the bill size was and just tried to get shots until i lost the bird. Pictures are not great, due to distance and manual or approximate focus. Looking at pictures on the back screen and then later at home, it became clear that it was a bulweria, a bit shocking as i had not really envisioned Bulwer's Petrel while watching the bird owing to size impression (i saw a few Bulwer's before and after during the trip but none was around the bird for direct comparison) and flight style (even in traveling mode, Bulwer's flight would appear more jerky with sharper turns, and if wheeling up and down it wouldn't go nearly as high as this bird did from my experience). The pictures tell a different story though, and at first glance they seem to show a Bulwer's Petrel. After close examination and comparison with online pics of both Bulwer's and Jouanin, a few points to mention nonetheless : - The bird doesn't show the paler coverts bar on the innerwing typical of Bulwer's (and absent on Jouanin), but some that can be rather indistinct on Bulwer's due to wear. - The bill appears consistent with Bulwer's rather than Jouanin, but bill thickness can be really hard to appreciate on distant/unsharp pictures, and the impression is different from 1 picture to another. I also ignore what the range of variation is for Jouanin on that account. - The body of the bird looks quite bulky for a Bulwer's and the neck quite thick, and the head shape looks rounded, lacking the squarish forehead bump of Bulwer's. - No "stepped tail" visible (as Jouanin would show according to descriptions, but browsing through pictures it's rarely apparent) - Visual impression of broad wings isn't consistently confirmed by pictures, but that's a tricky feature to judge. - Bird shows a pale spot at the base of the bill, a Jouanin feature according to some description, but it's not consistent across pictures. A strong morning light behind me created reflection effects that are probably not relevant to identification. I am fully aware that it will be likely impossible to confirm ID based on those pictures, but i thought it was important to document an unusual sighting, in particular from the observation of flight action. Bulwer's Petrel remains by far the most likely answer as Jouanin has never been recorded in Japan, but as detailed above, the features were atypical.

Technical information

Model

Canon EOS R5

Lens

RF800mm F11 IS STM

ISO

2000

Focal length

800 mm

Flash

Flash did not fire

f-stop

f/11.0

Shutter speed

1/2000 sec

Dimensions

927 pixels x 618 pixels

Original file size

384 KB