What makes them rare, why are they here, and how do we find them?
Birders are always on the lookout for rare birds. Some want to increase their life lists. Some are just in search of novelty. And then there is competition. But for all, there’s a sense of discovery in finding something unusual. Then too, there is a sense of adding to the body of scientific knowledge.
How does a bird get called a rarity? It might be out of its expected range. Its numbers might be so small that its population is trembling on the verge of extinction, or at the very least extirpation. Or it simply might not be expected in that place at that time of year.
When it comes to range, the rarest would be a new record, such as a first for the continent. Topping that list for Nantucket is the Western Reef Heron, a native of Africa that spent the summer of 1983 on the island. That was a first sighting for North America, and it took an expert on African birds from Philadelphia to identify it.
It appeared on the marsh in front of the University of Massachusetts-Boston field station in April, along with the usual spring migrants. At first glance it looked like a Little Blue Heron. But, it had bright yellow feet like a Snowy Egret. Was it a hybrid, a genetic mutation? What was it?
Once the visiting expert identified it, crowds of birders intent on putting a once-in-a-lifetime rarity on their North American lists descended. All the birding celebrities came to see it.
Visitors landed at the airport and had only to jump in a cab and demand, “Take me to ‘The Bird’.”to be whisked over to the field station. By the time the Reef Heron took off with a flock of Egrets in the fall, more than 1,500 people had seen it.
So, how did it get here? Did it fly all the way across the Atlantic? Did it hop on a boat? Ride a floating snag? We’ll never know, but a second one years later made it as far as Maine.
Another record long-distance migrant was a Grey-tailed Tattler, seen Oct. 19, 2012, during one of the late Vern Laux’s birding-festival weekends. Native to Siberia and occasionally seen in Alaska, its arrival on Nantucket was the first East Coast record. It was surprising because a related species, the Wandering Tattler, is more likely to stray further afield.
As it moved hither and yon around the harbor, birders chased it through the next three days, and many got to see it. Those who couldn’t get to Nantucket in time were disappointed. The bird moved on.
It was another case of having an expert in the right place at the right time. Simon Perkins, a guide with worldwide experience who had grown up on Nantucket, was scouting for the group and heard it calling at dusk. Without his depth of experience, it would have been easy to miss the Tattler or dismiss it as just a funny-looking Yellowlegs.
Other out-of-range species that have been seen on Nantucket include the Pacific Loon, Magnificent Frigatebird, Black-bellied Whistling Duck, Purple Gallinule, Black-chinned and Calliope Hummingbirds, Ash-throated Flycatcher, Western Kingbird, Sage Thrasher, Townsend’s Solitaire, Varied Thrush, White Pelican, American Avocet, Northern Wheatear and more. Clearly, Nantucket is a great place to look.
Although they can appear unexpectedly at any time, we most often search for rare birds in the fall. Fall is when birds are most abundant, as birds hatched that summer begin to move out on their own. Migratory birds head south, but even residents need room to spread out as they learn their skills and search for food.
Thanks to being an island 30 miles at sea, the ocean around us takes longer to cool than the mainland, giving a longer period of warmer weather. And thanks to the slower (some might say non-existent) arrival of spring here, plants get a later start and are likely to have a greater supply of fruits, berries and insects later in the year. Birds, too, look for the great restaurants, and nature provides them.
So, in the record-late department, we had a rare sighting of a Whimbrel on Dec. 16, 2018, which lingered until mid-January. The field-station marsh had twice frozen solid before the crabeating bird moved on.
For many years the assumption was that birds had very specific ranges, that they “belonged” in certain places, and did not belong in others. They were labeled “vagrants” or “accidentals.” It was thought that birds out of their range were “lost,” swept off-course by storms, or genetically defective.
Lately that dogma has begun to soften. Some ornithologists studying population, migration and rare birds now think that they should more properly be called “pioneers.” Although they do use changes in prevailing winds to move around, they are not disoriented. If they survive in a new location they may still migrate normally in the proper season. And if they can find, as one researcher put it, “a date for Saturday night,” they may be the founders of a new population. Rather than vagrancy, they reflect the marvelous adaptability of birds.
Researchers note that these records are often made by young birds dispersing. When their populations have an exceptionally productive year they may go further in search of territories of their own. Black-bellied Whistling Ducks and Ash-throated Flycatchers are notable examples.
Another is the Western Kingbird. Unknown in Massachusetts before 1887, it has increased in frequency since then. One is now found here almost every year in the fall. Spring records are more unusual, but it is probably only a matter of time before more of them find their way to this side of the Mississippi.
Other rare birds may not get as much sympathy, as their rarity comes from being endangered or threatened species. They may seem common or even abundant where they breed or winter, but their numbers are not always sustainable. Piping Plovers, American Oystercatchers, Roseate Terns, Red Knots, Shorteared Owls, American Bitterns, Saltmarsh and Grasshopper Sparrows may breed or rest on Nantucket during their travels.
Birders may make a special trip to see one or two of these species. But without protection their numbers will continue to shrink. For example, the Eskimo Curlew was once so common that hunters in the mid-1800s bagged them by the dozen. Yet none have been seen since one sighting in Texas in 1963. It is now considered probably extinct. So how will we know who gets to see the “last” Piping Plover or Red Knot? We probably won’t.
The sad truth is that more than half of most birds of the year do not live long enough to reproduce. But rather than becoming sentimental over the loss, we have to admire the amazing fecundity and adaptability of birds. And when we sight a rare one, admire its quest to survive. ///
Virginia “Ginger” Andrews has had a lifelong exposure to the world of birding, through her mother, the late Edith Andrews, a noted ornithologist. Ginger leads bird walks for the Maria Mitchell Association and writes “Island Bird Sightings,” the weekly bird column, for The Inquirer and Mirror, Nantucket’s newspaper since 1821.
