Date: 7/27/26 9:17 pm From: Alvaro Jaramillo via groups.io <chucao...> Subject: Re: [CALBIRDS] Tristram´s Storm-Petrel off Humboldt
HI Tristan
Nice analysis, I want to add that Markham’s in my opinion does not fly like a nighthawk. It flies in straight lines and has a relatively smooth and not all that deep of a wingbeat. It reminds one of the flight style of a Black/Brown Noddy. I down south right now, and hoping to see a Markham’s, hopefully I can confirm that in the coming days.
From: <CALBIRDS...> <CALBIRDS...> On Behalf Of Tristan McKee via groups.io
Sent: Monday, July 27, 2026 2:02 PM
To: calbirds <calbirds...>
Subject: [CALBIRDS] Tristram´s Storm-Petrel off Humboldt
This Saturday, 25 July 2026, Sean McAllister, Lucas Stephenson, Aidan Brubaker and I photographed a Tristram's Storm-Petrel northwest of the Eel River Canyon at 40.757332 N, -124.81674 W, about 28 miles offshore from the Humboldt Bay. The bird flew straight at the side of the boat and wheeled around almost overhead, circled a little more with somewhat bowed wings and mothy wingbeats, and then headed off far to the east in a low, direct style with rapid, fairly shallow wingbeats.
Identification criteria between this species and the Markham's Storm-Petrel are poorly developed, since the two taxa normally are found nowhere near one another geographically. This bird was somewhat worn in plumage and likely a subadult; it was less extensively gray and with a darker rump than in my experience with Tristram's in northwestern Hawaii or the Tristram's that Lucas and others documented off Marin last July, and this led us to seriously consider Markham's in the field. It was rather slender-bodied and very long-tailed. However, after review of the photos and videos and consultation with Todd McGrath, Logan Kahle, Ryan Terrill, Steve Howell, Peter Pyle, Rob Fowler, and others, we have a strong consensus that it was a Tristram's Storm-Petrel.
Key features indicating Tristram's rather than Markham's include a small amount of pale mottling on the sides of the rump (easily visible in Sean's photos but not mine), a short bill, and an exceptionally deep tail fork. The leg length and foot size may be important as well, but I haven't yet assessed how well this can be determined from photos (there is always the problem that seabirds hold the hidden knee joint in variable positions, altering field impressions). The flight style difference between the two species in calm conditions like ours seems to be quite striking and can be judged from videos; to my eye, Tristram's is reminiscent of a Lesser Nighthawk, while Markham's recalls a Common Nighthawk. Howell also pointed out that the lighter wing-loading of Markham's is characteristic of many Eastern Tropical Pacific species when compared to North Pacific species like Tristram's and Fork-tailed.
Compared to a Black Storm-Petrel, the short neck, thin bill, squarish head, grayish back, carpal bars extending out to the forward edge of the wings, thin body, and long, swallow-like tail made for a very striking bird. The legs and feet in the photos also appear considerably smaller.
Tristram's Storm-Petrel is a central and western North Pacific bird that was first documented in Calfornia at Southeast Farallon Island in 2006, and since then, accepted records are comprised of another there in 2015, one near San Nicholas Island in 2018, and one last year off Point Reyes. July seems to be a good time for it. Markham's is a species of western South America and the eastern tropical Pacific that has been recorded off western Mexico.
Eel River Canyon is proving itself to be one of one of the best locations on the west coast, for storm-petrels with flocks numbering in the thousands, recalling the old days at Soquel Canyon. Saturday´s bird was a bit further offshore, in the Leach´s zone, however.
