Words On Birds by Steve Grinley
Terns at the Mouth of the Merrimack
May, 19, 2023
by Steve Grinley
With the dredging complete, and the north end of Plum Island reopened, I thought now would be a good time to repeat a column from 2008. It is about the terns that fish the mouth of the Merrimack River, as they still do at this time every year:
Margo and I, along with fellow birder Phil Brown, headed for the north end of Plum Island. We wanted to investigate the hundreds of terns that were feeding daily between the jetties at the mouth of the Merrimack River. Though ninety-nine percent of them were sure to be common terns, we were hoping to find a less “common” tern such as a roseate, Forster’s, or black tern among them.
This evening was clear as we parked at the lot and walked out to the beach, which was lined with fishermen hoping for some stripers. We could see that hundreds of terns were near the end, and on the other side of, the Salisbury jetty, so we hiked down the beach to the Plum Island jetty and scoped across. It was still a long distance view and the late afternoon light was not helping. At one point, Phil thought he saw a black tern perched on the other jetty, but once it took flight we recognized that it was a common tern caught in the shadows.
We did get distant views of roseate terns, and a small number of them came closer and just a hundred yards offshore. About the same time, a fisherman, who had cast his line where the terns were feeding, started reeling in a fish. After a bit of a struggle, he landed what turned out to be a thirty-seven inch striper. Very nice. Aside from the few roseate terns we saw, the fishermen had better luck than us.
The previous Wednesday, Doug Chickering, of Groveland, was a bit smarter to observe the same feeding frenzy from the Salisbury side of the river and he reported what he saw:
“Lois and I , along with Bill and Phyllis Drew went over to the parking lot at the Salisbury jetty. This affords the best view of the mouth of the Merrimac River. I had told the Drew’s that I thought the chances of seeing a Roseate Tern seemed pretty good. It was just after low tide and with the shoaling at the mouth of the river we thought we might catch some terns feeding. Lois and I had come here a number of times in the late spring and summer and have been quite lucky in finding Roseate Tern. When we arrived there were plenty of terns; but they were way out at the end of the jetty and even in the good lighting pretty hard to identify; at least for me. We waited. I had been here enough times to know that with conditions like these things could change. And change they did. We first noticed that the terns and cormorants became more active; then they moved their activity from the end of the jetty to the mouth of the river; and we soon realized that they were approaching us.
“I am constantly amazed at how quickly and surreptitiously situations can change. We noticed a few terns flying up river, low over the water, then more flying past us, then suddenly they were reeling and diving right in front of us. The fishermen in boats followed them, and the fishermen on the shore began casting frantically. Like us, the fishermen were following the terns.
“What transpired for the next hour or so was one of those field events that almost defy description. We could trace the progress of the hunted fish by the rippling on the water and by the splashes when the hunter fish broke the surface as they drove the smaller ones onward. The terns, naturally were attracted by the turbulence. They knew what lay beneath. The converged and started feeding.
“There was both a frantic and transient quality to these feeding groups. They would slowly gather over a spot, start diving into it; be joined by dozens of others; then the mass of swirling birds would dissolve away to a dozen or so. Most of the time when I would focus on a single bird it had a fish in it’s mouth, but still flew around the spot as if reluctant to leave such a fine feeding place. The flocks dissolved, then reformed, grew to a crescendo, upwards of fifty birds, maybe more, then faded away again. At times there were three separate feeding groups; at times only one. The terns were often joined by gulls; mostly ring-billed, but some Bonaparte’s and even a single Laughing Gull made an appearance.
“We watched transfixed and amazed as the spectacle went on and on. There may have been some Forster’s Terns mixed in but the frantic flurry of activity; the profusion of birds and the somewhat tough lighting put identification beyond my already shaky powers. We did see two, unmistakable, unambiguous Roseate’s however. Unlike the Commons the Roseate’s didn’t hang around. As soon as they had grabbed a fish they were off; flying low and deliberately out past the jetty’s out to sea.
“I had told Bill and Phyllis that Lois and I had good luck with Terns here in the past, but none of us were expecting a spectacle of this magnitude.”