For a list of recent bird sightings, visit the Arlington Reservoir eBird Hotspot website!
Ducks of Arlington Reservoir
By John Andrews. This document first appeared in the Citizens for Lexington Conservation News letter, 10/23/20.
On a crisp November day the Arlington Res pulses with life. Mallards and Green-winged Teal rest on the shoreline as graceful Mute Swans glide by. The honks of an incoming flock of Canada Geese resonates across the water as they glide in and splash down . Further out, an elegantly-plumaged Hooded Merganser disappears under the choppy waves, only to emerge a minute later with a tiny silvery fish in its beak. These scenes are played out in a body of water that brings a spirit of wilderness into a tamed suburban environment.
The Arlington Reservoir is a natural treasure that spans the Arlington/Lexington border. In conjunction with the Lexington Community Farm that abuts it, it harbors the richest diversity of birdlife in the area.
Arlington manages the 65 acre central pond for swimming, fishing, and passive recreation. The mile-long walking trail that runs around the pond is heavily used by walkers, joggers, dog-walkers, and nature photographers. Despite the heavy human use, the reservoir attracts migrants in good numbers. Visiting early in the morning before human traffic becomes too intense offers the most surprises and can result in spotting such unusual visitors as Bald Eagle and Osprey.
For the moment, let’s concentrate on the waterfowl. You can find ducks and geese at the Arlington Res at almost any time of year. But it is during the fall migration, October-December, that the waterfowl diversity peaks. According to eBird, the birding database of the Cornell Laboratory of Ornithology [1] , some 31 species of waterfowl have been sighted at the Arlington Res over the past three decades. On any given day, a careful check of the shores and waves can easily record over 10 different species of ducks and geese.
It’s helpful to divide the waterfowl into three general groups: dabblers, divers, and Geese/Swans.
The dabblers are predominantly vegetarian feeders who spend their time in shallow water, sometimes eating floating weeds, sometimes pulling weeds from the bottom and grabbing an occasional insect or crustacean. They almost never go completely underwater, but tip up with their tails in the air. The males are often quite colorful while the females tend toward mottled brownish camouflage. Most dabblers are found in the muddy, shallow northern part of the Res or on the sandbars in the southwest area.
The divers are ducks that spend time in deeper water and dive down to the bottom searching for food. The mergansers are fish-eaters but other divers are looking for weeds growing in the deeper reaches. Divers prefer the deeper waters in the southern half of the Res and almost never come ashore.
Geese and swans are larger birds who pair for life. They feed on emerging vegetation in grassy areas and in shallow water. Sexes are similar. They can be found on sand spits or resting in deeper water. Often they come to the Res during the day just to pass the time before flying away to other feeding areas. It’s not uncommon to find a flock of over 200 Canada Geese at the Res.
Table 1 lists the Reservoir waterfowl species in decreasing probability of appearance. If you make regular visits to the Res, you should be able to see the species above the dashed line every year. In any given year it takes some good luck to log the species below the dashed line.
Conservation Issues
Because the Arlington Reservoir is heavily used, wildlife and people sometimes clash . Off-leash dogs can be a problem for waterfowl trying to use the shores and sand spits as resting places. The water management policies adopted by the Town of Arlington impacts the availability of the mud flats favored by ducks and shorebirds. Hopefully a balance can be maintained that allows people to enjoy the Res while maintaining its extraordinary value for wildlife.
- - - -
John Andrews is a Lexington resident who has been birding at the Arlington Reservoir for over 40 years.
Birds and Birders of the Arlington Reservoir.
Karsten E. Hartel, April 1999
This report is presented to establish baseline data on important aspects of the Arlington Reservoir; namely, 
the great abundance and diversity of bird life that can be seen in the area and use of the site by birders. This report is written to document the value of the site in these regards.
The Town of Arlington owns the Reservoir and all of the immediate land surrounding it, including an extension along Munroe Brook. The area is under the management umbrella of the Arlington Public Works Department. The Arlington Park and Recreation Commission has jurisdiction over the swimming area. Since the Reservoir is situated in both Arlington and Lexington, its wetland status is under the jurisdiction of both Arlington and Lexington Conservation Commissions. The ecology and public use of the area points out the need for a comprehensive management plan for the area. Indeed, goals in that plan could well include enhancement of the area for wildlife.
Birds
The Arlington Reservoir is an important migratory area for many waterbirds and the surrounding uplands provide fair to good habitat for songbirds. Nearly 150 species of birds have been seen in the immediate area (see a full list on the left). The habitat is probably the "wildest" in Arlington and its diversity attracts the birds even though the Reservoir was artificially created.
The seasonal fluctuation in water level creates good three seasons of spectacular birds. It draws diving ducks and grebes (in the deep end) and dabbling ducks, shorebirds and herons around the weeds and mudflats (shallow end). There are no other habitats quite like these elsewhere in Arlington. At times the Reservoir draws a wider variety of waterfowl than the Great Meadows National Wildlife Refuge in Concord.
Birding
Over the last ten years, birding, or in other words observing wild birds for enjoyment, has grown immensely in popularity. A recent survey shows that there are an estimated 54 million participants in this endeavor in the United States. This survey also shows that birding is participated in by more people than such traditional outdoor activities such as hiking and camping. The number of people fishing or bicycling only exceeds the number birding by three to four million participants.
In April of 1999, a survey of subscribers to local bird listservers were asked how often they visited the Reservoir between Spring 1998 and Spring 1999. The responses show that the 76 birders spent 1060 birder visits to the Reservoir. The respondents (and the people who might have been with them) probably represent only a small portion of the birders visiting the Reservoir. Expanding the sub-sample to a total estimate is difficult, but a few thousand day visits is not out of the question over a period of a year. Surely this outnumbers the fisherpeople and maybe even the recreational walkers using the area.
Autumn Birding at the Arlington Reservoir.
Elizabeth Karpati, 2004
The Reservoir Comes to Life
The water level in the Res is rising, and so is the bird population.
There are some large rocks on the emerging sandspit opposite the beach. One day last week a Great Blue Heron stood tall on the biggest rock, like a sentinel watching over the crowd of Mallards, Canada Geese, and gulls resting on the sand and occasionally slipping into the water.
In the shallows at the northern end of the Res another Great Blue stood in water almost up to his heels (which are in the middle of his long legs), fishing. On the mudflats along the berm two Ring-billed Gulls were engaged in a shouting match which eventually got physical: they seemed to be trying to bite each other’s bills until one gave up and flew away. A fat Herring Gull stood nearby, ignoring the combatants completely.
Noisy Killdeer were running back and forth among more resting Mallards. A few American Wigeons mixed with more Mallards and Black Ducks in the water. Tiny drab ducks swam among them, and one flashed an emerald wingpatch, confirming my suspicion that they were Green-winged Teal out of breeding plumage. Two oddballs stood out on the mudflat: duck-shaped but distinctly larger, all black with a hint of green sheen on their heads. Probably strays of some domestic breed, or hybrid descendants of strays.
Off to one side a beautiful Yellowlegs was foraging, unperturbed by my slow progress along the berm. I couldn’t tell whether it was a Greater or a Lesser, but its legs were certainly bright yellow.
The final treat was a young Green Heron fishing near the end of the swimming area. Every feather was clearly visible in the sunshine: the dark greenish head, rusty-brown sides of the neck, streaked throat and breast, slightly speckled sides, and dull gray back which seemed to belie its name. Its feathers may have fallen short of adult coloring, but it was already an effective hunter: it gobbled up three small fish in quick succession, zip-zip-zip, then strutted about a bit before catching a slightly larger one. It was fishing in an oval patch where the outflow from a drainpipe had pushed away the floating vegetation. The water in this patch looked strange – almost milky in one area, brownish in the other. I hope there was no contaminant in it to spoil the young heron’s lunch.
Peterson’s field guide devotes two pages to pictures of “confusing fall warblers.” Amen to that characterization. It’s fun to meet the challenge of identifying tricky birds, but it is also fun just to observe the easy ones that conveniently parade before you.