Monday, March 12, 2018

Spring Blitz Primer

We have been running pelagic birding trips off Cape Hatteras in spring for 25 years now. Prior to that I led some spring trips off NC for previous trip operators, as early as 1990. I began organizing spring trips off VA in 1987. It started as an effort to see a few seabirds that were seldom seen on summer pelagic trips. We were looking for species such as Leach’s Storm-Petrel, Long-tailed Jaeger, South Polar Skua, and Arctic Tern. Our wish list off NC included Red-billed Tropicbird, known just from a few records back then. What we have found since those humble beginnings has been even more diversity than we expected. Trindade Petrel, Fea’s Petrel, and Bermuda Petrel became big drawing cards here by the late 1990s. Of those, only Trindade Petrel was on the AOU checklist when we began. We have also found three species of storm-petrels that were not known to occur here. One of these, the European Storm-Petrel, is now found almost annually as a result of our intensive chumming, days at sea, and careful observation. Even on days when no rarities are found, a diverse list of species is possible and it is not unheard of to see 12 to 15 species of pelagic seabirds in a day between mid May and mid June.

Many years ago we were running these trips mostly on weekends, but that changed over a decade ago when we acquired our own vessel. No longer in need of larger parties to fill a larger boat, we started to spread the passengers over a greater number of dates. This evolved into something that was dubbed the “Spring Blitz,” where we have offered (and run) as many as 19 consecutive pelagic trips from Hatteras. Running so many trips gets to be a grind, but the opportunity to go out day after and day and observe the parade of seabirds that pass offshore of Cape Hatteras keeps us going. The diversity goes up and down as the wind shifts around the compass and the Gulf Stream changes course and speed. We have a special opportunity to get in touch with what’s going on out there that cannot be had when you are just a weekend warrior. Every day is different because not only are birds are on the move, but the water is moving too. The Gulf Stream sometimes flows at a clip of four knots out past the edge of the continental shelf, so even birds that are rafted up are on the move. As such, we can go to the same places and see different things from day to day. Offshore fishing is here works much the same way. People see some good reports posted and they have great expectations for the following day. Often it’s just the reverse.  A slow day can or follow or precede an epic day of fishing or seabirding. That’s one reason why we encourage people to sign up for at least a couple of trips, either back to back or with a day off in between.

Knowing what to expect is key to making the most of your experience offshore. Many of our clients come prepared, having studied the possibilities well beforehand. Things can happen quickly on a pelagic trip. We can lure a variety of species closer to the boat with our chum, but there is no guarantee that a bird will take more than a passing interest. And when you increase the wind a bit, you will appreciate the time spent studying. That’s not to say we don’t help our newcomers get a handle on what’s being seen. Our trips are known for setting the bar when it comes to that business. Just keep in mind that you will derive more satisfaction when your preparation meets opportunity. Some species will be seen in numbers, but when the first Fea’s Petrel in three days comes by at 40 mph among half a dozen Black-caps, it’s helpful to know to look for dark underwings. To help with preparation, we have compiled this annotated checklist of spring seabirds, with some commentary on their status so you know what should be on your radar. There are plenty of good guides to help with ID and we have hundreds of images of birds seen on our trips at our blog site. Perusing this blog will give you an idea of age classes that might be expected as well as molt timing, which can provide quick clues as to whether you are looking at a Band-rumped or a Leach’s Storm-Petrel on a spring trip.

Before we get to the list of birds, be aware that seabird migration is not necessarily direct nor is it locally consistent from year to year. We are looking for birds that wander vast distances across ocean basins during their non-breeding seasons. Some of these birds also travel many hundreds of miles on foraging trips while they are nesting! Many of these species are sailing birds, and as such they plot their course based on the winds. Wind can be beneficial for seeing gadfly petrels, but other species, such as jaegers and terns might be found in better numbers during periods of light winds, especially if the wind direction tends toward shore. Our daily reports also provide insight into why we saw what we did on a given day, based on the weather patterns and the flow of the Gulf Stream. The weather is different every spring, so it’s not usually helpful to plan based on the dates from just the previous season. To do so is almost always the wrong approach. It’s far better to stick with the long-term results, which we draw from in this annotated list of pelagic seabirds from spring trips off Cape Hatteras.

List of Spring Seabirds

Northern Fulmar can be fairly numerous some years into April, but is hardly ever encountered past mid May. In 2005, we saw fulmars well into May.

Fea’s Petrel is a rare but regular visitor off Cape Hatteras from mid May onward into summer. May and June are the best months and it might be found on 20 to 40% of the trips in a given spring. What we see here are probably almost all Desertas (aka Bugio) Petrel, a cryptic species not yet recognized by the ABA as distinct from the Cape Verde population. Alan Brady and I got the first photos of Fea’s in the Western North Atlantic here off Hatteras on May 24, 1992. Fea’s Petrel occurs here on a variety of wind directions. The odds of seeing it go up with wind intensity, but we have found it on several light wind days.

Bermuda Petrel nests less than 600 nautical miles from Hatteras, but it primarily ranges toward the Azores. It is also quite rare with just over 100 breeding pairs. Nevertheless a few birds visit our waters. If we run 15 spring trips, we might see it on one or two trips or not at all. Like Fea’s, we have seen this species on some days with westerly winds. I got the first at sea photos taken anywhere of the species off Hatteras on May 26, 1996. Image below is from May 25, 2015.

Trindade Petrel forages extensively in the North Atlantic from at least May to September, but is generally found far out to sea. Easterly winds greatly increase the odds of finding this species. We have seen it on as many as 40 to 50% of trips some years but on a few years it has gone unrecorded in late May and or early June. Dave Lee collected one off Hatteras in August 1978 and Killian Mullarney got the first photos on a trip with Bob Ake off Hatteras in May 1991.

Black-capped Petrel is the signature species of the Hatteras Gulf Stream pelagic trip.  It is a scarce seabird that nests at just a few mountain sites in the Carribean, but its’ fast, high arcing flight makes it a conspicuous part of the Gulf Stream avifauna. Most trips encounter at least a couple of dozen, but there are days when we see just a few. We’ve only missed it just once in hundreds of spring trips. We see good numbers of Black-caps on westerly winds. Blue water is best, but they can also be found in smaller numbers when the Gulf Stream takes a queer turn. Black-caps we see here show a lot of variation, particularly in the extent of the cap and the dark bars on the underwing and it’s not yet if that is related to their breeding distribution, past or present.

Cory’s Shearwater typically arrives off Hatteras in mid May and numbers quickly increase by early June. It can be scarce in the early 20s of May. Southerly winds are good for bringing Cory’s to Hatteras in spring, and they are often found well inshore under such conditions.

Scopoli’s Shearwater is considered by the AOU to be a subspecies of Cory’s Shearwater, but nearly every other taxonomic committee considers it to be a valid species. We see it here sparingly in the spring, but it does occur with regularity and it is more common during the summer. Identification is still being worked out and some individuals are hard to place. Our experience suggests that Scopoli’s might be more of a boat follower than Cory’s, and it might be more likely to feed offshore.

Great Shearwater can be seen here in late May but is more reliable in early June. Wind and swell play a big role, and if the wind is offshore, this species is harder to find in May.

Sooty Shearwater is seen off Hatteras mostly in the last ten days of May. The timing of the flight and the proximity to shore varies from year to year depending on the wind and swell. Easterlies mean more Sooties and good flights can be seen from shore on very light southeast winds.

Manx Shearwater is generally more in evidence if there is a good flight of Sooty Shearwaters in progress, but it can also be found among flocks of Cory’s, Greats, and Audubon’s in the Gulf Stream or on its own offshore. Overall it’s a good bird here in spring, seen on about 15 to 35% of trips depending on the year.

Audubon’s Shearwater is expected although numbers vary from just a handful some days to a few dozen. On rare occasions it may number in the hundreds, as it is did for a couple of days in May 2017. A good accumulation of Sargasso Weed and southerly winds are helpful for seeing numbers of Audubon’s in spring.

Wilson’s Storm-Petrel is usually the most numerous species on our spring trips and we generally see a hundred or more each day. We tend to see better numbers when the wind is from the north. In 2017 we had more a more westerly flow than usual and numbers of Wilson’s were way down from the long-term average.

European Storm-Petrel occurs almost annually and has been seen from May 18 onward into early June, with a single record in July. Most of the records fall between May 29 and 31, but in 2005 we saw it on the four trips we ran between May 30th to June 5th.

Black-bellied Storm-Petrel has been seen off Cape Hatteras on May 31, 2004, June 23, 2007, July 15, 2006, and August 14, 2010. These are the only records for the western North Atlantic. The late Capt. John Gallop spotted the first one and all of the others to date were spotted by Kate Sutherland.

Leach’s Storm-Petrel is uncommon in spring and whether we see them comes down to the conditions. Easterlies bring them in and strong westerlies send them out to sea.

Band-rumped Storm-Petrel comprises a number of as cryptic species in the North Atlantic. Some of these have not yet been formally named. These birds actually nest in the same burrows at different seasons in the Azores and perhaps other islands. It seems that we have two types here, but the molt timing is such that we are only able to decipher that during late May and early June. Age of the birds in question compounds the problem. This will always be a vexing ID problem away from the breeding grounds. We see Band-rumps on nearly all of our spring trips. The great majority are presumably winter breeding adults undergoing primary molt.

Swinhoe’s Storm-Petrel has been seen here three times between June 2 and 9. We also saw one off Hatteras on August 8, 1998. All four of these records are documented with photos and two of the birds responded well to our chum. It’s certainly a small sample, but all of the June Swinhoe’s were seen on days with NW wind. The only other Swinhoe’s from the western North Atlantic was the first one, seen by Ned Brinkley off Oregon Inlet, NC in August 1993.

White-tailed Tropicbird is quite rare here before June, but the odds go up when we have southeasterly winds. We saw several birds here in late May and early June 2011, but that was exceptional.

Red-billed Tropicbird is rare but regular here from mid May onward. Many of the birds we have seen at sea have been short-tailed, yellow-billed immature birds. An adult has been known to visit Cape Hatteras several times in recent years between mid March and late May. Usually seen on 15% of trips or less.

Masked Booby is mostly a summer visitor to the Gulf Stream here, but we have seen it several times during spring over the years. Photo by Peter Flood.

Brown Booby seems to be increasing here in recent years, but it remains a very rare spring visitor, perhaps more likely in June than May.

Northern Gannet is a common to abundant winter resident and spring transient around Cape Hatteras. A few stragglers occur, mostly near shore well into spring.

Red-necked Phalarope is a common spring migrant off Cape Hatteras, but is seldom seen much past May 20.

Red Phalarope is a common winter resident and spring transient off Cape Hatteras, but departs even sooner than Red-necked Phalarope, and is hardly ever seen on our spring trips.

Laughing Gull is very scarce offshore here in spring. They are often non-descript looking first summer birds.

Sabine’s Gull is a great rarity here in spring. I’ve seen it just twice in mid to late May and there are few other spring records.

Sooty Tern is seldom seen offshore here before July. In May 2003, we had an unusual incursion of Sooty Terns for a few days following a strong blow from the southeast. Photo by Kate Sutherland.

Bridled Tern is found on about 25 to 40% of spring trips and almost always in low numbers. First summer birds are what we usually see in spring, and they are generally found in association with Sargasso weed and flotsam.

Roseate Tern is a good find here offshore in spring. Perhaps we would see it more often if we had more trips in early May. Most years we do not see it.

Common Tern is regular offshore in spring. We see it on the majority of trips in May and a large minority of trips in early June.

Arctic Tern is generally seen on less than 40% of our trips in late May and less than 30% of our trips in early June, but if conditions are favorable they might be seen daily for a few days. This of course means they can be missing for several days if the wind is offshore.

Brown Noddy is very rare here and has been seen well on just a couple of spring trips off Cape Hatteras. Photo May 31, 2017 off Hatteras by Steve N.G. Howell.

South Polar Skua has been seen on 20 to 25% of our spring trips over the years. Easterlies increase the odds and at times they can be seen well inshore of the Gulf Stream.

Pomarine Jaeger is usually the most likely jaeger to be found offshore. The long-term odds are 40 to 70% overall. With easterly winds, it’s pretty much guaranteed, but with westerlies it can be quite scarce.

Parasitic Jaeger is usually the least encountered jaeger offshore in late spring, and many of the ones we see in the Gulf Stream are young birds and harder to separate from Long-tailed than adults. Seen on just 15 to 30% of the trips overall. With easterly winds a sea watch can be a better way to find them here.

Long-tailed Jaeger is found on 20 to 40% of spring trips. Easterlies are best, especially light southeast winds. At such times it can be seen well inshore of the Gulf Stream and it has been observed flying over Cape Hatteras. Long-tailed birds (mostly second and third cycle) predominate in mid to late May but by early June we see mostly late first cycle birds.

Except for the Manx Shearwater, all of these images were captured on our pelagic trips off Cape Hatteras. I hope that you can join us sometime to see the diverse array of seabirds that we encounter here during the spring.

Good seabirding,

Brian Patteson