Late August is the beginning of my favorite birding season in Washington. It is the time of year when nearly all our birds are on the move and the potential for finding a surprising migrant is high. I recently moved near Carkeek Park in northwest Seattle so I had been looking forward to seeing what the park is like during fall migration. The previous week I had stopped one day before work without seeing much of interest but on August 31st, 2017 I figured I would give it another shot.
Carkeek Park has a creek that flows out into Puget Sound that attracts waterfowl, gulls, and some shorebirds so I decided to check there first. To reach the beach and creek mouth one walks over an overpass to cross the railroad tracks and from there I could see there was a flock of gulls near the creek mouth. I gave the flock an initial scan and estimated there to be about 160 California Gulls plus a few of the larger Western/Glaucous-winged Gulls mixed in. While counting I was keeping an eye out for other species, but realized it would have been easy to miss a smaller gull in the mix. I was hoping for a Franklin’s Gull, an unusual fall migrant in Puget Sound, but was also interested to see if there were any of the more common Ring-billed or Mew Gulls mixed in. About halfway through the flock on my more careful second scan I saw a different bird facing left that had a black head and a black bill with a pale tip. The bird was dark gray and the eye was ringed in bright red. I stopped, totally stunned. I recognized the bird right away as “that South American gull, what was it? Swallow-tailed Gull?”, but that made no sense. I looked again, took a couple photos with my phone, and hurried down the stairs and across the beach to get a better view. Sure enough when I looked again it was still there. Apparently I wasn’t dreaming.
I took a few more pictures and searched for “Swallow-tailed Gull” online to verify that I had the name of the species correct. My phone was running low on batteries so I texted several friends the photo and was able to send an email to Tweeters to alert the birding community of its presence before my phone fully died. I was also able to get in touch with my wife Evie who was able to swing by on her way to work with my camera so that I could get some better photos of the bird. Evie was there within ten minutes, even beating the rush of birders that began streaming in just after her departure. The whole flock flushed at one point so I was then able to see the Swallow-tailed Gull in flight. It’s a stunning bird when perched but even more so in flight. I was able to stay a couple more hours before heading into work. By the time I left about 40 other birders had arrived including two who had taken the ferry across from Bainbridge Island. By early afternoon people from southern British Columbia, Yakima, and Portland had seen the bird and there was talk of people flying in from out of state in hopes of a sighting.
Over the next few days, the Swallow-tailed Gull was found daily, but has not returned to Carkeek Park, as of 5 Sep. The eBird map of sightings shows the bird’s favored location at Point Wells, as well as the other two locations where it has spent a day, at Carkeek Park and at the Everett marina. Presumably it forages at night offshore in the deeper waters of Puget Sound, and returns to these areas to roost for the day.
Just how rare is this bird? Very rare. On a global scale, the species occupies a limited range, breeding primarily on the Galapagos Islands and also on Malpelo Island off Columbia. It’s non-breeding distribution is almost entirely at sea, primarily in the Humboldt Current off South America. The population is also relatively small, estimated at 35,000 individuals by Bird Life International in 2012. Seeing it anywhere in its range requires some planning and a lot of travel. In Central and North America, it is extremely rare. There are a handful of records from central American countries (NAB 62: 489 and eBird), and only two prior records for North America, both from central California. One was seen 6-8 Jun 1985 at Point Pinos and Elkhorn Slough, Monterey Co. and the other was seen on 3 Mar 1996 at sea off the Farallon Islands, San Francisco Co. The Puget Sound bird is the furthest north record in the world, and the first North American record in two decades; and is an extraordinary opportunity to view a bird that has a small population and a very restricted range.
What about the status? While there is no question about the identification of this bird, there are unanswered questions about its origin: whether it arrived in Washington of its own volition or whether it was transported for some or all of the distance between its normal range and Puget Sound, or whether it was an escapee from captivity. Similar questions were raised about the first California record; the debate over its origin lasted for a decade until the second report was received. Don Roberson provides a good summary of the debate, and the arguments for natural origin that ultimately convinced the California Records Committee to accept it as probably of natural origin. The evidence that he cites could be applicable to this bird as well, as the 2015/2016 El Nino event was one of the three strongest on record. The 1985 Monterey record followed the 1983 El Nino event, another very strong one. Howell et al (2014) note a pattern of seabird dispersal following food-web crashes in the Humboldt Current, and in that context, the recent record of a Nazca Booby, also a seabird of the eastern equatorial Pacific, in the central Gulf of Alaska on 30 Aug is intriguing. Although these pieces appear to support they hypothesis of natural origin, the Washington Bird Records Committee will need to check to see if any facilities in western North America keep captive Swallow-tailed Gulls and have had any escape in recent years, and will also need to consider the ship-assisted hypothesis, before voting on whether to accept this record as natural origin. Hopefully, it won’t take the Washington Committee as long as it took the California committee to render a judgement!
Article by: Ryan Merrill with additions by Bill Tweit, Washington Department of Fish and Wildlife
 Howell, S.N.G., I. Lewington and W. Russell. 2014. Rare Birds of North America. Princeton University Press, Princeton, NJ. 428 p.