The Prospect Park Progne: a Mega Martin Mystery

As the doldrums of March draw to a close, spring migration begins to heat up a bit more rapidly. The excitement of the May peak is still a ways out, but the rising anticipation in both birds and birders is palpable. This year, April kicked off with a bang of legendary proportions! The morning of the 1st brought clouds and light drizzle after a night of southerly winds. I was out at Astoria Park, searching for new arrivals and documenting breeding behavior, when I received the fateful message from Doug Gochfeld on the Kings and Queens bird alert service.

Immediately, my curiosity was piqued. Doug is a keen observer who has birded all over the world, and his commitment to careful identification and thorough documentation is exemplary. Anything that gives him pause is sure to be worth a second look, especially if it’s unusual enough to warrant a notice for the entire community. There is only one member of the genus Progne that can be expected in New York, or indeed the entire United States: the familiar Purple Martin. The species is a noteworthy find anywhere in Brooklyn, generally appearing as a passage migrant or post-breeding disperser from nesting sites in nearby counties. For some reason, however, Doug had hesitated to write this individual off as “just” a Purple. In the early afternoon, he reasserted his suspicion that the bird was something out of the ordinary in an email to the New York State listserv. The developing intrigue was too much for me to resist. I gathered up my gear and set off on the subway to search for the mystery martin myself.

I arrived at Prospect Park just after 4 PM, easily finding the assembled crowd of likeminded birders who had gathered to see Doug’s discovery with their own eyes. It was quickly apparent that all lenses were trained on a flock of swallows foraging over the southwestern cove of Prospect Park Lake. It didn’t take long for me to pick out my quarry, as the martin was showing cooperatively a stone’s throw from the shoreline.

I took note of the bird’s field marks as it dipped low to the surface of the water and wheeled overhead in wide arcs. The most prominent feature was its clean white belly, lacking the obvious dark streaking on the underparts of a Purple Martin. The upper breast, throat, and flanks were dusky gray-brown, while the topside was blackish with an iridescent blue sheen. Though it was larger than the Tree, Barn, and Northern Rough-winged Swallows it was associating with, the martin was smaller overall than I had expected. Most Progne species, including Purples, tend to dwarf other swallows, but this individual didn’t stand out so dramatically. The light forehead and pale gray collar of a female Purple were also conspicuously absent, replaced by faint ghosts of the same patterns on the darker brown head. With all of these traits taken into account, it was clear why Doug had sounded the alarm on this bird. 

It was a pleasure to see a number of friendly faces on the scene, including Brendan Fogarty, Ryan Zucker, Ryan Mandelbaum, Tripper Paul, Menachem Goldstein, and Gabriel Willow. The presence of Shai Mitra and Pat Lindsay drove home how monumental this sighting was, as I knew they wouldn’t have driven all the way from Suffolk if they didn’t think this was something worth chasing. The air of excitement hanging over the lakeshore was electric, amplified by the continuing incredible views of the bird. Everyone commended Doug for his discerning eyes and thanked him for getting word out promptly, then the discussion tentatively turned towards identification. There are 9 species in the genus Progne scattered across the Americas, and they can be notoriously difficult to separate in the areas where their ranges overlap. Figuring out the identity of a vagrant individual was certain to be a challenge. At the time, we focused our efforts on obtaining as many photos as possible to adequately document the martin. I enjoyed a few more moments with the bird at the eastern end of the Lake on my way out of the park, finally heading home as sunset drew near. 

We were all relieved to learn that the mystery martin was found again the following morning, especially the birders who had been unable to drop everything and chase on the first day. The bird wound up sticking around at Prospect Park until the afternoon of April 4th. Over the course of the weekend, observers accumulated a wealth of beautiful images from a variety of angles, including crisp flight shots as well as perched comparisons with other swallows. Vocalizations were also heard on several occasions, and Doug managed to secure a short recording of its calls. We were fortunate that our guest was so remarkably confiding, giving us a fighting chance in the identification effort thanks to the abundance of high quality media birders were able to procure. 

The first putative ID suggested for this bird was the “Snowy-bellied Martin” complex: a loose association of species that includes Caribbean, Cuban, and Sinaloa Martins. It seemed like a logical possibility, considering that these species are all found not far to the south of the ABA Area borders. The brilliant white underparts of our bird certainly seemed to fit, too. However, further observation and investigation revealed that the visiting vagrant’s characteristics didn’t quite match up with this group. Caribbean and Cuban Martins are comparable in size to Purple Martin, with Sinaloa measuring only slightly smaller. This didn’t mesh with the relatively tiny stature of the Brooklyn bird. Furthermore, all three of these species have long tails with deep forks, in contrast to the short, shallow-notched tail of the mystery martin. They also show well-defined boundaries between the white belly and the dark brown of the throat and flanks, again contradicting the more gradual blend with a dingier grayish color seen in the New York specimen. A number of knowledgeable birders, including Doug, began to suspect that the widespread Gray-breasted Martin of the Neotropics might be a more suitable candidate for this individual’s identity.

The saga of this intriguing identification challenge attracted attention from a diverse array of experts in the birding community. Internationally renowned biologist Alvaro Jaramillo provided a number of resources to help put the difficulties of Progne ID into context, including an explanation of the poorly understood taxonomy of Gray-breasted Martin subpopulations. Birding author Kenn Kaufman dropped into one of the discussion threads to comment that this well-documented individual could, in time, help us better understand the criteria for distinguishing tricky vagrant martins in the field. I was put in touch with researchers from the Purple Martin Conservation Association, who shared images with their international contacts and voiced their support of the developing consensus. Inspired by some preliminary discussion of audio analysis with David Andreas Tønnessen, I decided to dive into comparing the Brooklyn recording to vocalizations of other Progne species from Cornell’s Macaulay Library. Although calls within this genus are variable and broadly similar, Doug’s sample seems to consistently match best with Gray-breasted Martins of the nominate subspecies from Middle America. I compared the tape to examples from Belize, Costa Rica, Panama, and southern Mexico, and all showed a similar spectrogram with tightly-packed, descending “slash marks” and a frequency range between roughly 2 and 6 kHz. All in all, the growing body of evidence strongly favors the identification of this bird as a Central American Gray-breasted Martin, Progne chalybea chalybea.

It’s crucial to note that this identification effort is ongoing, including continued correspondence with experts from the Neotropics, comparative review of collected media, and examination of existing study skins at the American Museum of Natural History. Due to the blurred lines within the genus as a whole and the species in particular, proper documentation and organization is imperative for presenting the case to the relevant records committees. That said, the combination of structure, plumage, vocalizations, and other details suggest that the other species of Progne can be eliminated as options with some confidence. The only prior confirmed occurrences of Gray-breasted Martin in the United States are a pair of specimens from the Rio Grande Valley of Texas, both from the 1880s. That makes the Prospect Park bird one of the rarest vagrants I’ve ever observed in the ABA Area, and a mindblowingly insane addition to my New York State list. My past encounters with the species took place during my April 2019 trip to Panama, where it marked a milestone as my 800th life bird. I never would’ve predicted it would gain additional significance nearly 2 years later, just a few miles from home.

It’s also worth noting that my observation of this magnificent martin took place just a few days after I marked the anniversary of my first fire escape stakeout in Astoria. The stark contrast between the limited scope of my peak quarantine vantage point and the exciting, community-wide investigation of this unexpected megararity provided a welcome reminder of what makes birding so wonderful. It also offered a bit of hope for brighter days ahead, with migration continuing to ramp up and the potential for travel opportunities approaching on the horizon. A Code 5 vagrant at the start of spring is going to be a tough act to follow, but I still can’t wait to see what the coming months bring our way! I’ll also be keeping an eye out for future updates on the martin ID saga; my personal NYSARC report is drafted and awaiting finalized details for submission!