ArrayJanuary 29, 2010 at 4:08 pm
Maine Heron Observation Network
Burying Island, a Heronry of the Past
[caption id="attachment_176" align="alignleft" width="125" caption="Photo by Steve Perrin"][/caption] The following was written by Steve Perrin, a long-time observer of one of Maine's largest great blue heron colonies... Great blue herons maintained a heronry on 30-acre Burying Island in Taunton Bay, Maine, from roughly 1959 to 1999. Every year they’d follow the frost line up the coast, arriving on or about the first of April. Pairs would mate on the outer branches of red and white spruce trees shortly thereafter, build and refurbish nests, and incubate typically five eggs in each nest. Juveniles fledged in mid-August. Much of the colony stayed on the bay until the shoreline began to freeze in late December. Then they’d fly to warmer climes, I never knew where. I was privileged to live from June 1986 through December 1988 in a one-room cabin I’d built on the island. Three families owned the island in undivided shares, and granted a conservation easement to the MDIFW in 1984. The heronry was in the 15-acre parcel designated a forever-wild sanctuary. Living close by, I had ample opportunity to observe the herons flying, feeding, nesting, loafing, and dealing with hungry bald eagles, classified as fish eagles, but having an acquired taste for herons and ducks. [caption id="attachment_177" align="alignleft" width="115" caption="Photo by Steve Perrin"][/caption] When pursued by an eagle, flying herons had an emergency maneuver in which they would up-end one wing and drop the other, effectively spilling the air that provided lift so they would abruptly drop 20 or 30 feet, then pull up heading along the back azimuth of the direction they’d been flying—leaving the eagle above them in cold pursuit of a phantom. This was no ad hoc tactic; I saw juveniles practice it several times in succession until they got it right. The only flaw being that if they had to repeat the maneuver, they lost so much altitude they sometimes couldn’t do it one more time. Four or five to a clutch, nestlings were more vulnerable. I saw one eagle on a branch near a nest with two immature herons fending it off, repeatedly stabbing with their bills by thrusting their necks forward again and again for half an hour, the eagle staying just beyond reach, the pair exhausting themselves, eagle then swooping in and grabbing each bird by the neck in its talons. No sound is more pitiful than the outraged klaxon a heron sounds in the clutches of an eagle. [caption id="attachment_179" align="alignleft" width="113" caption="Photo by Steve Perrin"][/caption] In the early years, I estimate the heronry contained well over 200 nests, producing an average of three or four young in each. By 1993 it was down to 96 nests by actual count (after the herons had flown). In 1999, I saw 50 herons (25 pairs) abandon the heronry when attacked by one eagle. In early April I was out in my peapod and saw the whole thing. The herons had arrived from the southland the day before, looking exhausted by their trip. Apparently, the eagle saw them too. Having built two nests on the island, it was waiting for them. When it arrived for lunch the next day, the entire colony took to the air, milled just above the trees, squawked loudly, and abruptly struck farther east in search of safer quarters elsewhere. I never found out where they went. Their guano killed the trees they nested in, which eventually blew down, and have yet to grow back. When they do, perhaps the herons will try again, which would be unlikely if the eagle is still around. The herons seemed to rely on their numbers for protection. Each day, adults would fly off in every direction to find food, sometimes being gone for several hours, leaving their young largely unprotected except in a statistical sense by the occasional bird returning to feed the young in one nest or another. When a parent would near the heronry with a full gullet, it would emit a solitary “grawk,” which its own nestlings would always identify (I could tell by their sudden signs of alertness and anticipation) and all others ignore. [caption id="attachment_180" align="alignleft" width="150" caption="Photo by Steve Perrin"][/caption] But adults didn’t simply put dinner on the table. They made their young earn it. In fact, they made it as difficult as possible by perching on the edge of the nest, raising their bill skyward, then waiting for one or another of the young to force their neck downward so food would spill into the bottom of the nest. The most aggressive of the clutch would perform this service by grabbing the adult’s bill in its own, then dragging and twisting it against a show of resistance until the adult’s bill pointed down, releasing a morsel of fish, frog, eel . . . whatever. At which point the adult would lift its bill and restart the whole exercise, ceasing only when other nestlings had had a try and its gullet was empty. Nestlings in adjacent nests (sometimes only two or three feet away) staring into the middle distance all the while as if food meant nothing to them. My favorite time of year was mid-August when hundreds of fledglings would fly to nearby ledges, gracefully pose for my photographs, then fly back to the nest to get fed. At first they hadn’t a clue what they were supposed to do once out of the nest, much less how to feed themselves. But in a few days they caught on and began wading in the shallows, feinting, then thrusting their bills toward small fish. Their maiden flights and landings tended to be awkward, but they learned by doing and quickly refined their skills, coordinating feet-wings-necks like their role models. Everyone loved watching the herons. Binoculars lay on every windowsill facing the bay. But even when the colony left, there were still harbor seals, loons, mergansers, scaup, goldeneyes, hawks, and yes, eagles, hungrier perhaps, but magnificent nonetheless. I still see the occasional heron, particularly feeding on the flats at low tide. Retrieving a benthic thermometer last year, I was surrounded by five herons fishing in nearby eelgrass meadows, like old times.
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