Mourning Doves

Mourning dove (internet download)

Recently, our backyard revealed a ‘puddle’ of feathers about a yard across. Best guess is that a hawk had caught and killed a mourning dove, and then proceeded to pluck feathers before flying away with the carcass.

Mourning doves – older names turtle dove and Carolina turtledove – are a common bird across America, with a population estimated at 300 to 400 million birds. Doves are a light grey and brown in color, with only subtle differences in appearance for males and females. Mated pairs are monogamous. Two eggs are laid per nesting cycle. A pair will raise several broods each year. Both parents participate in nest building, egg incubation and feeding the chicks (also referred to as squab). Although doves feed on seeds and grains, very young chicks are not fed seeds, but rather a protein- and fat-rich secretion from the parent birds’ crop, called “crop milk.” [The crop is a pouch just below the throat. Many species of birds can fill this with food to digest later or else regurgitate into their chicks’ mouths.]  As chicks get larger, seeds the parents have swallowed into their crop are combined with crop milk. With such a rich diet, chick fledge – are able to fly – within two weeks from hatching. The parents will continue to feed them for an additional week or two, but will have also laid eggs for the next brood.

In captivity, lifespan can approach 20 years. This, plus all the fecundity would cover the countryside knee-deep in mourning doves, except that predators find them easy to catch. In the wild, average lifespan is less than two years. Ravens and crows take chicks from nests, fledged chicks are easily caught by many predators, and adults end up in the food chain because they are ground feeders. Prior to European colonization, the major predators of adult dove were hawks and falcons, attacking from above. Add to that cats (pet and feral), and the life of a dove can be brutally short.  

Feathered evidence of a hawk kill

The predator that left us the feathered evidence was most likely a Cooper’s hawk. This is a relatively small but very agile hawk that preys primarily on birds. Red-tailed hawks are larger, but a bit too slow to be bird predators, preferring instead rabbits and squirrels. The other possible culprits would have been peregrine falcon, or sharp-shinned hawk, but these are relatively rare in eastern Massachusetts. In addition to doves, Cooper’s hawks will also prey on robins, starlings and sparrows – also ground feeders. Attacked birds are taken either on the ground or while trying to take off. One estimate has each hawk killing on average two birds a day.

In describing mourning doves, John J. Audubon wrote “Whenever it starts from a tree or the ground, on being unexpectedly approached, its wings produce a whistling noise, heard at a considerable distance.” This is an example of “sonation,” defined as sounds produced by birds, using mechanisms other than the vocal organ. Humans make sounds by means other than voice: we snap our fingers, clap our hands, slap our thighs, stomp our feet and click our heels. For some bird species the sound making is voluntary, typically related to males claiming territory or their mating display. The male palm cockatoo of New Guinea uses a claw-held stick to drum on a hollow tree he has selected as a possible nest site. The female, attracted by the noise, checks out the real estate.

For mourning doves, the taking off sound is involuntary but mallable. Birds often form flocks to increase collective vigilance, thus allowing early detection of predators. This benefit of sociality relies on rapid transfer of information. For many species, an alarm call, but for pigeons and doves, one of the flight feathers on each wing is modified so that on take-off, with the wings fully extended for extra lift, the modified feather rapidly flutters against the next feather during the wings’ downstroke, making an easily heard noise. This noise is present whenever mourning doves take off, but if the cause is alarm from detecting a predator, wings beat faster and the pitch is higher. Taped recordings of regular and alarmed take-offs confirm that other doves respond more to the sound of alarmed take-offs.

Is this altruism or self-interest? Assuming this evolved under predation by hawks, one bird taking off from a group on the ground may just be making itself the best target. But if all the birds take off, the visual complexity of the group may cause the attacking hawk to lose sight of an individual bird, and perhaps even miss all of them. Once in the air, mourning doves can reach speeds in excess of 50 miles per hour. Bye Bye Birdie.   

For mourning doves, much like robins, migration is optional. Given enough food, males of both species will remain behind, forming loose flocks of 10-30 birds. Their reason for not leaving is to have dibs on the best territory when the females return in the spring. Robins will find and plunder berries such as winterberry and Asian bittersweet. Mourning doves will seek out remnant grains in farm fields and cluster under birdfeeders to benefit from what perching birds have spilled to the ground.

Lastly, from James Lipton’s “An Exaltation of Larks”: a group of doves is called a "dule," (pronounced ‘dool’) taken from the French word deuil (mourning), because “The soft, sad ululation of the dove has always evoked the sense of mourning.”

Ruby-throated Hummingbirds

"Why is this bird different from all other birds?" Hummingbirds represent an evolutionary expansion into a niche frequented by flower-pollenating moths and butterflies. Downsizing and an elongated beak and tongue combination allows these birds to feed on flower nectar. The adaptation initially took place in tropical climates where the ability to retain body heat – typically a function of larger body size – was not critical.

More than 300 hummingbird species inhabit the Central American tropics. Only 16 frequent the U.S., and of these only one species - the ruby-throated hummingbird - migrates east of the Mississippi River. The rest go west. The risks of a longer eastward migration are offset by having a monopoly on the hummingbird niche once they arrive.

Painting of a male Ruby-throated Hummingbird

Ruby-throated hummingbirds winter in Mexico, then migrate as far north as Canada in the spring. Their journey begins with gorging on insects until body weight is almost doubled, then launching into a night-long flight from the Yucatan peninsula of Mexico to the U.S. Gulf Coast. The fuel for this comes from gorging on small insects and flower nectar. Once over land again, they revert to daylight eating every 10-15 minutes, consuming more than half their body weight over the course of each day.

In eastern Massachusetts these birds are in residence from May through September. The slightly larger, less brightly colored females arrive a week or two after the males. Males do not help with nest construction, egg incubation or feeding. Hummingbirds do not flock. A yard with multiple feeders can be host to several birds at the same time – a “charm” of hummingbirds – but in reality, what is seen is a temporary truce around a shared resource. Each bird, sated, goes back to its own territory.

Females lay two eggs. Nests are the size of a ping-pong ball, eggs the size of a coffee bean. Gestation is two weeks. Chicks are ready to leave the nest three weeks after hatching. Fledgling survival to adulthood is high compared to other species, and lifespan about five years if the fledglings survive the first migration. By comparison, a nesting pair of golden-crowned kinglets (a small, Maine-dwelling bird twice the weight of a hummingbird) will hatch two broods over the course of a summer, each numbering 8-10 fledglings, yet only one or two survive to the following year’s breeding season.

Hummingbirds are omnivores - they get carbohydrate calories from flowers - but all of their protein, fat, vitamins and minerals from eating gnat-sized insects. Sugar-water feeders supplement the energy needs also met by flower nectar. A well-managed feeder should attract visitors from May to September. For a natural alternative, plant monarda, honeysuckle, trumpet vine, and other hummingbird-friendly perennials. Do not use pesticides, as these will kill the small bugs hummingbirds also need to consume. Feeders do not deter hummingbirds from the urge to migrate south in the fall. 

Ruby-throated hummingbirds have some interesting dependencies on other species. Males arrive in the northeast before most of the flowers have opened. Instead of relying on nectar, the birds also feed on tree sap from holes drilled in trees by yellow-bellied sapsuckers. Females construct nests incorporating spiderweb silk.

Part of mural on the building at the corner of  Parker 
& Waltham Streets = male, broad-billed hummingbird.

In addition to small size and hover capacity hummingbirds employ an unusual energy conservation strategy - extreme body temperature modulation. During cool summer nights these birds allow their body temperature to drop from 105 to about 70 degrees Fahrenheit. Resting heart rate drops from 500 to 50 beats per minute (rate while flying can exceed 1,000). Without this trick of lowering energy expenditure via torpor they risk overnight starvation. Muscles are rewarmed in the morning by shivering.

Maynard is blessed with a hummingbird mural on the south side of the building at the corner of Waltham and Parker Streets. The bird in question is a male, broad-billed hummingbird, a species that winters in central Mexico but migrates as far north as southern Arizona during breeding season.   

A version of this column was published in 2012

Ecological Succession

In 1859, Henry David Thoreau wrote an essay called "The Succession of Forest Trees" in which he described succession in an oak-pine forest. "It has long been known to observers that squirrels bury nuts in the ground, but I am not aware that any one has thus accounted for the regular succession of forests." His essay was more about replacement than succession as that term had come to be used in modern ecological studies. He first observed the obvious – that many tree seeds are designed to be transported by wind, also that the small seeds of wild cherry, wild grape and various berries can be consumed by birds and other animals and defecated elsewhere. (We know that Oriental bittersweet berries are consumed by robins and spread that way.)

Wreath of Oriental bittersweet vines, with berries. In the
spring, returning robins perched on it to eat the berries.

Thoreau also described the less obvious, how, for example, oak seedlings might emerge from the soil after a pine tree forest was cut. Some botanists of his era took the position that acorns could lay dormant in the soil for decades, even centuries, but when the forest trees above them were cut, be viable, triggered by sunlight. Thoreau observed, rather, that even in a mature pine forest, there were oak seedlings amongst the underbrush the result of squirrels burying acorns or else dropped by blue jays and other birds. The same dispersion seen for beech, hickory, chestnut and other nuts.

Ecological succession is the process of change by all species (plants, animals, bacteria) of a community over time. During the first half of the twentieth century, succession theory was dominated by the idea that for a given location there was a convergence toward a climax community regardless of the starting conditions, that, for example, that moist-soil lowlands in eastern Massachusetts would always end up as a forest dominated by sugar maple and beech trees regardless of whether the starting conditions were abandoned farmland, fire, flood or hurricane. Similarly, a drier, hilly terrain would always end up being pine/oak. In this school of thinking, a climax forest was a stable, interrelated community with a near-constant total biomass – trees dying being replaced by the same species.

Current theory allows for more complexity and chance. In these models the finding of certain species being found together is because terrain and climate are beneficial to each species individually without ‘community’ interaction. In both models, prolifically reproducing and fast-growing species will populate a disturbed area first, followed by shade-tolerant, slower growing but more competitively successful species. American beech is an example of an extremely shade-tolerant tree that can abide in the understructure for years until a break occurs in the canopy.    

One point that has become clearer is that it is not just about plants. The local extermination of beaver changed terrain. The return of same created wetlands and flooded ex-forests. The local extermination of deer allowed for lush undergrowth and greater survival of tree seedlings. The present-day surfeit of deer in New England – now at a population higher than before the European colonists arrived – is denuding all the undergrowth. Trees that were part of the North American mosaic got diseases. American chestnut trees are long gone, native dogwood, ash and hemlock are struggling. Invasive species challenge the status quo. Climate change is affecting the entire biome.         

Dandelion: The common dandelion (Taraxacum officinale) was introduced to
North America be English colonists in the early 1600s as a medicinal plant.

In Maynard and Stow, some of the best evidence for ecological succession is abandoned farmland. Some of this was seized by the U.S. Army via eminent domain during World War II, subsequently allows to go to forest, now the Wildlife Refuge. The trees are all around 70-80 years old. There is not a lot of dead wood on the ground. Same for the Summer Hill forest. The woods traversed by the Assabet River Walk, once pasture, are older. There, there are many downed trees in varying states of decay.   

The greenspace bordering the Assabet River Rail Trail was cleared during construction. Dandelions, an exemplar of windblown propagation, are common, as are other early-growth perennials. Tree seedlings are present. Without maintenance of borders, our trail could become a green-flanked, green-roofed tunnel. An excellent report “Rail Trail Maintenance and Operation: Ensuring the Future of Your Trail – A Survey of 100 Rail Trails” suggests that trails need roughly $1,500 per mile per year in maintenance and operating costs. Maintenance tends to be a combined effort of municipal budgeting and volunteer organizations.

Assabet River Revisited

Recently, the Assabet River has been deeper than its long-term average for spring the reason being more than average rainfall. April, for that matter most months, averages four inches of rain (or snow equivalent) per month, year-round. Eastern Massachusetts does not have wet and dry seasons typical of some other parts of the country, although in some years there can be lengthy summer droughts. Oddly, after an unseasonably warm and low-snow February and March, this April was one of the coldest on record.    

Kayaker enjoying the rapids between Main Street
and foot bridge, Spring 2014

In the spring the river is exceptionally clear. The bottom is stony, versus how green it will appear in late summer when grown over with water milfoil, filamented algae and other bottom-anchored water plants. Year-round, the water has a low sediment content. This is because the Ben Smith Dam traps all the upstream sediment. A U.S. Geological Survey study completed in 2003 estimated accrued sediment volume at approximately 20,000,000 cubic feet. If ever there was a decision to remove the dam, some form of sediment removal would be required, elsewise vast quantities of sediment would shift down river, increasing the risk of floods in Maynard, Acton and Concord.

This time of the year the river mid-town is also mostly clear of surface plants. By late summer, every rain event that increases volume over the top of the dam brings floating plants like duckweed, watermeal and globs of free-floating algae through the center of town. Upstream of the dam, the near-shore shallows, also currently clear, will be covered by these floaters plus the flat leaves of white and yellow water lilies. Luckily for boaters, most of the river is deep enough to not sustain the surface-leafed, bottom-rooted, water plants.

The kayak and canoe launch dock at Ice House Landing
is back in the water for 2020.

Come winter, the plants will die, returning phosphorus to the bottom sediment. Even though wastewater treatment facilities are enjoined from adding too much new phosphorus to the river, this growth/death process functions as a self-sustaining cyclical phosphorus source, promoting next spring’s growth. Bad now, far, far worse 40 years ago. Ann Zwinger wrote in A Conscious Stillness (1982) "...the reach above the Powder Mill Dam [Acton, next to Route 62] is closed by joint action of the Maynard and Acton boards of health...the river smell is nauseating, reeking like an unpumped-out campground outhouse times ten." The smell emanated from rotting of bacteria, algae and water plants, the consequence of eutrophic growth promoted by the excesses of phosphorus and nitrogen entering the water as either inadequately treated waste water or farm and golf course fertilizer run-off, raw storm sewer discharge, etc.

As for why “Assabet,” once upon a time the Assabet River was known as the Elizabeth River, alternative spellings Assabeth, Asabet, Elizbeth, Elizabet…all thought to be Anglicized versions of a Native American name. One colonial era map had it as the Concord North River, with the Sudbury being the Concord South River. There was a map consensus in 1830 that Elizabeth Brook flowed into the Elizabeth River, but by 1856 it was Assabet Brook flowing into the Assabet River, with the pre-Maynard community identified as Assabet Village. Nowadays it is Elizabeth Brook flowing into the Assabet River.   

Removal of the footbridge, August 2016, in preparation for the new bridge,
installed February 2017 as part of the Assabet River Rail Trail.

The river is 31 miles long, from headwaters in Westborough to its merge with the Sudbury River in Concord to form the Concord River. Seven towns draw their well water from within the Assabet valley watershed and five discharge treated wastewater into the river (Westboro, Marlboro, Hudson, Maynard, Acton). There are six existing, intact, historic mill dams, plus one breached (Damonmill, West Concord) and one flood-destroyed (Papermill, Maynard). And there are two twentieth century flood control dams: George H. Nichols, Westborough, and Tyler, Marlborough. By having limited egress, those function to blunt peak downstream volume during times of heavy rain.

Sadly, in this time when so many people are looking for places to hike, there are few in Maynard or Stow with an actual view of the river. A suggestion: drive west on Concord Road into Acton, south on High Street, veer right onto Old High Street, and park at the trail head. The trail goes west, with water views.  

Decorated Tree in the Woods

On the Assabet River Walk trail, which can be accessed from Concord Street or Colbert Avenue, there is a fifteen foot tall spruce tree. It is the only spruce tree in the entire forest. This December, for the third year in a row, it has been decorated with more than 100 red, silver and gold bulbs. Toward the end of January almost all of the bulbs will be removed. Until then, anyone essaying a walk in the woods gets a surprise. Walking in from the Colbert Avenue end, there are silver decorations every 20-30 yards, in tree branches above or alongside the trail, decreasing in distance between them as the decorated tree nears. Think 'breadcrumbs,' marking the way.

UPDATES: January 18th, before storm, all silver and gold removed (except near the top, which will require a ladder). Also most of the 'breadcrumbs.' February 8th, removed all but about 20 of the red.

Sometimes winter adds its own decorations in the form of a dusting (or more) of snow. With a bit of snow only the red bulbs stand out, the silver and gold lost against the white snow.

With a lot of snow the whole tree folds up sort of like an umbrella. Snow-covered or not, best effect achieved by approaching the tree from the Colbert Avenue end in the afternoon of a sunny day. Distance from trailhead is about 1/3 mile along a root strewn trail. After rain or thaw there are soggy sections, so best to visit when the ground is dry or frozen.

Mid-January : all non-red bulbs (around 2/3 of total) removed except at top (because that will require  carrying in a ladder). By end of January most of the red will be removed, but a dozen or so will remain until next December. 

The River Rises and Falls

From the late 1700s onward the Assabet River was less of a river and more of a series of narrow ponds, each created by dams that first backed up water for seasonal usage by saw mills and grain mills, those dams or their replacements later put into service for factories of the Industrial Revolution. Given the dams, the river was not a useful means of transportation either for people or freight; instead the river’s watershed became crisscrossed by railroads.

Figure from 2011 book "MAYNARD: History and Life Outdoors"
shows water precipitation in inches per month and average river volume,
also by the month. Snow expressed as water inches.

Mill operations were initially all about how much water could be retained. With a sufficient supply, mill operations could be year-round rather than limited to the times of naturally higher water flow (late fall through late spring). When partners Amory Maynard and William Knight bought land in Assabet Village they also bought water rights upriver, include rights to dam up Boon Pond and to the Fort Meadow Reservoir in Marlborough. One nice thing about water power was that once the dam, canal and waterwheel were in place, power was basically free. Within years, however, the demand for power was such that instead of relying wholly on water, coal-powered steam engines were soon supplementing and then replacing water power.    

Ben Smith dam in drought conditions. Click photo to enlarge.

As to how much water flows in the Assabet River, a U.S. Geological Survey station (https://waterdata.usgs.gov/nwis/uv?site_no=01097000) located a short distance upstream from the Waltham Street bridge provides depth and flow information. The long-term average volume is 200 cubic feet per second (cfs). As the figure shows, March and April are the high-water months as a result of snow melt plus rain falling on frozen and therefore non-absorbent ground. July through September are the low-water months despite basically the same amount of precipitation every month, because of evaporation and transpiration (water molecules released into the air from plant leaves). A prolonged drought can reduce flow to under 20 cfs. An interesting legality here in Maynard is that while Mill & Main owns the millpond, it is restricted from diverting water into the canal that provides water to the millpond when flow volume falls below 39 cfs. The intent of the law is to prevent the river going dry for the section downstream from the dam. Only when the river rises, as it did after the October 17 storm, is Mill & Main allowed to top up the pond, and perhaps simultaneously release water from the east end, so as to both refresh and replenish the millpond.

The river also rises and falls after each rain storm. Case in point – after that October storm the river rose from 1.5 to 2.8 feet deep at the USGS gauge. Pre-storm volume was 30 cfs, peaking at 260 cfs about a day after the storm ended. There was then a days-long gradual decline toward pre-storm levels, reversed when rain started the night of October 22. Interestingly, a look back at historic floods finds that there was often a previous significant rainfall event that had saturated the ground and raised water levels in the river just before the big storms that pushed the river into flood. For those floods, the most recent in 2010, flood crest levels occurred three days after the heavy rains began. Sometimes the skies had cleared and the sun was shining while the water was still rising.

River depth markers painted on wall below John's Cleaners on Sept 22, 2019.

White paint markers spaced one foot apart were recently painted on the wall below John’s Cleaners, visible from the sidewalk on the north side of the Main Street bridge. These indicate how deep the water is at the wall. Nine feet is optimistic (or pessimistic, depending on hour you feel about floods), as for flood peaks measured at the USGS station, there have only been five that topped seven feet since 1942. Because river width is different at the gauge and the bridge, we don’t know yet how closely the two indicators comply.

There once was, actually, a bit of Assabet River boat transportation. From 1906 to 1914 there was steamboat service from a boat house near the Ben Smith dam, Maynard, and a landing wharf was installed at Whitman's Crossing near Lake Boon, Stow. The one-way cost was twenty-five cents. Disembarking at the crossing, a short walk brought people to a dock on Lake Boon, where a regularly scheduled steam launch would travel to docks along the shore, allowing people to reach resorts, club houses and lakeshore summer homes.

Painting River Depth Markers

The Assabet River, as it flows through Maynard, has an average volume of 200 cubic feet per second (cfs). Month-by-month, March and April average 400 cfs, while July, August and September average under 100 cfs. Drought can drop flow to 20 cfs. There is an internet-accessible gauge of river volume and depth, found by searching on USGS Assabet. The default is showing the last seven days of data, but a larger number of days can be selected.

At 100 cfs, depth is 2.0 feet, 200 cfs = 2.5 feet, 300 cfs = 3.0 feet, 400 cfs = 3.5 feet,
1,000 cfs = 5.0 feet, 1,700 cfs = 6.0 feet, and 2,400 cfs = 7.0 feet. The last significant flood was spring 2010, 2,500 cfs = 7.1 feet.

Wall under John's Cleaners, bordering the Assabet River in Maynard, MA, as
seen from the middle of the Main Street bridge. Click on photos to enlarge

While checking USGS Assabet is rewarding to data advocates, the idea of providing a publicly seen measure of water depth was a challenge. One location seemed ideal - the wall under John's Cleaners, bordering the Assabet River, next to the Main Street bridge.

Walking in the Assabet River from Tobin Park (north of the Rail Trail bridge)
 to the Main Street site, where a ladder had been lowered by rope.

As this was to be a very public project, seeking permissions seemed like a good idea. Queries to Town of Maynard management, including Department of Public Works and Conservation Commission, resulted in conditional approval. Facts learned in the process were that the Commonwealth of Massachusetts 'owns' the water in the river, the Town owns the land under the river, and private property owners own land down to mean high water. What this meant was that John's Cleaners owns the wall, so permission was sought there, also. Finally, the project was proposed to the Board of Selectmen - and approved. A waiver was signed to absolve the Town of any liability in case of injury.

Using duct tape to attach a stencil to the wall. Two stencils were created, each five feet long
one taped above the other. The material was FedEx boxes. Making the stencils took four hours.

Stencils were created from FedEx corrugated boxes, incorporating five inch tall number stencils. Creating the stencils took about four hours. The duct tape and stencils were lowered by rope from the bridge. Discarded after the one-time use.

The paint use was Benjamin Marine D.M.T. Acrylic "Safety White,"
suitable for use in places that will be wet or under water.

From arriving at the site to completion of the painting took about one hour, including the walk in from and out to Tobin Park, which was over water-plant slicked rocks under one to two feet of water. The ladder was needed to tape and then paint the top of the upper stencil.

About to paint the top markers and numbers. Nine feet was chosen because since record
keeping began in 1942, no flood has exceeded nine feet, and only five have exceeded seven feet. 

Water depth records collected by the U.S. Geological Survey (USGS Assabet) are for the gauge near the 7-11 store, and thus water depth at the bridge is not an exact match. The USGS defines the Assabet River as being in flood stage when depth exceed five feet. This happens at least once almost every year.

Wall painted, stencils removed. Except in time of extreme drought
the water is never low enough to paint a marker for one foot.

Historically, for floods for which water depth was measured, Hurricane Diane raised the river to 8.94 feet (at the gauge) in 1955. Floods in 1968 and 1979 reached 8.1 feet. Floods in 1987 and 2010 reached 7.1 feet. Volume at that 2010 flood was recorded as 2,500 cubic feet per second.

The wall, with water depth markers.

River depth is of interest to kayakers. Currently the river between the Ben Smith Dam and the east side of Maynard is blocked by many fallen trees, but if ever cleared (by Town of Maynard, or a significant flood), it is possible to kayak through town - under the bridges - when water depth is more than 2.5 feet and less than 4.0 feet. Too low, get stuck on bottom. Too high, get stuck under bridges.

Swans on the Assabet River

Mute swan at rest, Assabet River, Stow, MA

Mute swans reside on the Assabet River, either as solitary birds or nesting pairs. These swans can occasionally be spotted from the Ice House Landing dock, but will always be seen when kayaking or canoeing upriver into Stow.

Swans are long-lived, and return to the same nesting place. Of the 5–8 eggs laid each spring perhaps 1–3 cygnets will reach maturity. Unlike Canada geese, parent mute swans do not allow the yearlings to return to the same area the next spring, so in any summer the local populations are either solitary birds or parenting pairs with the new cygnets. Hatchlings start off gray in color, not turning white until their second year. They can paddle about within days after hatching, but need 60 days to mature enough to fly.

In flight, swans make Canada geese look small and slow. Low-flying geese meander about at 20–30 miles per hour. Higher-flying geese, the ones actually migrating, are at flock speed of 35–45 mph. In contrast, once swans have powered up they are doing 50 mph. At more than twice the weight of a ten-pound goose and with a wingspan of almost eight feet, this is one impressive bird. The wings of mute swans in flight make a distinctive whooshing sound that on still mornings can be heard more than half a mile away.

In the U.S., mute swans do not migrate southward. Come winter, they shift to the ocean shore, where they may congregate in groups. Come spring, the existing pairs head back to their nesting waters, while the three year-olds will be pairing up for the first time before seeking nesting waters of their own. Lifespan in the wild can by 10–15 years. Swans will often stay in mated pairs for many years, but if one dies, the other will take a new mate. And they are not actually “mute,” as they can hiss, snort, yip and so on; it’s just by comparison their not being as loud as North America’s native trumpeter swans.

The business end of a mute swan (internet download)

Boaters of any type should not approach mute swans during nesting and cygnet-raising seasons. These birds are SERIOUSLY territorial. On land or on the water, males act to prevent any animal or human from getting near the nest. That yard-long neck may look like a cute sock-puppet, but it is wielded more like a poking, pinching hand, combined with hard blows from the forward edge of the wings. Swans have been known to attack dogs and children. Swans have been known to attack swimmers, canoes and kayaks. Swans can sink jet skis, flip ATVs and down ultralight aircraft. OK, maybe not those last three, but really, leave nesting swans alone. There is one reported instance of a man (not wearing a life jacket) knocked out of his kayak and drowned by a nest-protecting swan.

Mute swans are not native to North America, and in fact are viewed as an invasive and destructive species because of their voracious appetite for aquatic vegetation and harassment of other water bird species. The first introductions were in New York state prior to 1900. Escaped swans initially established feral populations along the Hudson River, Long Island Sound and Chesapeake Bay, but have since spread to the Mid-west and North-west regions, numbering in the tens of thousands and increasing by more than 10 percent a year. A single mute swan can consume four to eight pounds of plants a day. Continuous feeding by a flock of mute swans can destroy an entire wetland ecosystem.

Various state programs attempt to control local populations. Some states along the Atlantic coast have hired professional hunters. Another control method is to coat the eggs with corn oil, which will prevent hatching (removing the eggs triggers the female to lay replacement eggs).  

“But they are really pretty.” Yes, they are. Mute swans were imported from England starting in the late 1800s as living ornaments for private and public garden ponds. The Swan Boats in Boston Public Garden are modeled on mute swans, right down to the orange beak and half-raised wings. Swimming, mute swans hold their heads curved down a bit rather than looking straight forward. Mated pairs oft face each other in the water, so in silhouette their necks and heads make a heart shape. The website www.savethemuteswans.com takes the position that mute swans are in fact native to North America, and thus deserve the same protections as native birds.

A Dearth of Trees

Maple Street, Maynard, 1910. Second tree on left appears to
be same tree as in photo below. Click on photos to enlarge.

Using Maple Street, Maynard, as a perhaps not entirely typical example, there is strong evidence for attrition of the urban treescape. A postcard in the collection of the Historical Society shows both sides of Maple Street (and the east side of Brooks Street) lined with maple trees; a 1910 photo shows the same trees  on Maple Street, larger, and allows for an estimate of perhaps forty trees at least six inches in diameter. Today, 110 years later, only four survive – one slowly dying. The greenway between the street and sidewalk contains these plus three replacement trees. The business district has suffered a similar loss. Roughly fourty sidewalk squares along Nason, Main and Walnut streets plus grass islands in the municipal parking lots were designed to host trees; many are treeless. Lastly, construction of the Assabet River Rail Trail through the center of town resulted in the loss of more than 600 trees more than four inches in diameter. Replacement plantings were perhaps one-fifth that number, and most of those north of Summer Street.

Maple Street, Maynard, 2019. Sickly tree on left is one of the
originals, most likely planted when houses were built in 1870s.

In addition to deliberate deforestation, our trees are at risk to species-specific diseases, invasive insect species, invasive plant species, uncompensated storm damage and deferred maintenance. Nationwide, chestnut blight took out three billion trees, elm disease another one hundred million. The larvae of Emerald Ash Borer have a fatal impact on ash trees, as does the Hemlock Woolly Adelgid on hemlocks. Oriental bittersweet vines grow into the tops of mature trees, overshadowing the trees’ leaves and breaking branches with weight, until the trees die.

Urban trees have value. A study conducted at Devens, MA, concluded that house prices in tree-rich neighborhoods are higher, energy costs needed to cool houses when trees provide share are lower, and asphalt streets have a longer lifespan before repaving is required due to a dampening of the daily heat/cool cycle. Trees capture rain, reducing the needs to channel and process stormwater runoff. Trees provide shade for outdoor activities, and muffle street noise. Plausible research suggests that patients in hospitals need less of pain relief meds and heal faster if their windows look out over gardens and trees versus a parking lot.

Nason Street, Maynard: stump of
removed urban tree. Eleven replace-
ment trees will be planted soon.

Counter to this, there is persistent lack of funding for urban forestry, consequence of tight budgets and an attitude that trees are “nice to have” but not necessary. Once a town or city has fallen behind maintaining an existing urban canopy, reversing the trend with an accelerated planting program is seen as too expensive. Only when a community recognizes that the commercial and personal health benefits of a trees sustainability program are real and important do annual budgets reflect the need. As of 2019, Nason and Main streets have lost most of their sidewalk trees.  

Norway spruce trees flanking house,
Glendale Street. 

Not only is Maynard suffering from a dearth of trees, it has no examples of remarkable trees. A pair of Norway spruces on Glendale Street approach 100 feet. There are sugar maples and white pines here and there that top 100 feet. Prior to the arrival of European colonists, New England’s white pines could top 160 feet, sugar maples 135 feet, eastern hemlock 130 feet, and tulip poplar trees 120 feet. Groves of 100-foot tall trees with trunks exceeding three feet in diameter were common, likewise trees 300 to 500 years old.    

The dearth of big trees rests on our history. To the colonists of the 1600s, every tree deserved an ax. Wood burning for household heat was so profligate that visitors from England wrote home that people were so extravagant as to having more than one fire burning at the same time! By 1850, more than half of New England was field or pasture, the remaining forests were second or third growth, good for firewood but not lumber. Locally, much of what had grown in abandoned farmland was leveled by the 1938 hurricane. A fair guess is that Maynard is home to no trees more than 200 years old, and that the majority is under 100 years old. What we have are adults with growing ongoing.

European copper beech, Acton Street, Maynard, MA.
Estimated 90' tall and 90' wide. 

EXTRA: there are two European copper beeches that may be the largest-trunked trees in Maynard. One is next to St. Bridget's Church. The other is in a side yard on the west side of Acton Street. The oldest known introduction of copper beeches to the United States dates to around 1830. The church beech may have been planted when the building was completed, in 1884. It has a girth of 14'11' at four feet from the ground, meaning a diameter of roughly 4.75 feet. European beech trees can reach ages of 250 to 300 years and diameters of 10 feet, with a few exceptional trees exceeding 500 years and diameters of 20 feet. Maynard's two stately copper beeches will likely be with us and holding us in awe for decades into the future.

The Town was designated a Tree City USA in 1999 and 2000, and refiled the necessary documentation for re-certification in 2001. Allowed to lapse, but applied and approved in 2016. The DPW Highway Department is responsible for the maintenance of all public shade trees.

Short Stories

In Oak Park, Illinois, a car stops at a traffic light, an older and a younger man in the front seats, a young woman in the back. She opens the door, steps out, tosses a keychain into a storm drain and gets back into the car. The light turns green.

Great Blue Heron with catfish
(Click on photos to enlarge)

In Boca Raton, Florida, a Great Blue Heron caught a catfish as large as its head. Standing in the water, it spent minute upon minute upon minute repositioning the fish in its beak, at times shaking the fish, placing the fish on the shore to start over, or dipping it in the water.

A bicyclist is riding the wrong way on a one-way street, next to the line-up of parked cars. A pedestrian steps out…

A bicyclist is riding the wrong way on a one-way street, next to the line-up of parked cars. A car door opens…

A bicyclist is riding the right way (with traffic) on a two-way street, next to the line-up of parked cars. A door opens…

Griffith Park, entirely within the City of Los Angeles, has signs at every entrance warning visitors that the Park contains rattlesnakes. One LA newbie exclaimed “Why did they put rattlesnakes in the Park!?” The answer was that the snakes were there long before it was designated a park. Snakes can strike to a distance of 1/3 to 1/2 body length. More to the point, snake strikes occur in one-twentieth to one-tenth of a second, whereas human reaction time is about one-fifth of a second. Snake beats human every time.

In addition to rattlesnakes (and coyotes), Griffith Park is home to one male mountain lion known as “P22.” The lion has a GPS tracking collar, so park staff know its location at all times. This did not prevent P-22 from entering the Griffith Park Zoo in March 2016, scaling a fence, then killing and carrying off a koala. P22 has TWO Facebook accounts.

The Assabet River rises after every rainstorm, after every snow-melting day. During winter weeks the water level can slowly drop while the air temperature is below freezing. Along the branches of trees that have fallen into the river, icicles form. Rather than tapering to a sharp point, the bottoms are blunt-ended, terminating just about the water’s surface. In sunlight, a long row of these, each several inches long, look like the pendant glass of a chandelier, shimmering white.

Great Blue Heron preparing
to swallow fish

The same river, summer, observed from a bridge: there are fish down there, swimming just fast enough to counter the flow of the sluggish low-water river. The fish are doubly camouflaged. From above, the dark upper surface blends into the dark tones of the river bottom. From below, silvery scales blend into the brightly refractive surface of the water above. One way to spot fish is to look for shadows on the bottom, then find the fish above.

Get in the habit of throwing food scraps out the back door and there will be visitors. Footprints from cats, skunks, raccoons and opossums can be differentiated in a night’s dusting of snow. The morning after tossing out some lamb shanks a murder of crows was working over the remains, scattering when a pair of ravens dropped in.  

Great Blue Heron
swallowing fish

One sunny late August day, gusting cold front blowing in, water temperature in the 70s but air temperature in the low 60s – the result for one small-boat sailor tacking into the wind was gradually progressive hypothermia. Each splash of water felt warm on a cotton T-shirt. Between splashes, evaporative cooling chilled. Physical clumsiness set in, and a touch of mental fog. A gust tipped the boat over. Swimming to the overturned hull, flipping the boat back upright and climbing in was more wearying than it should have been. Same the second time. The sailor turned toward home, miles away.       

Roadside, rural Pennsylvania: A fawn was thrashing about in the ditch next to the road, unable to stand, legs broken from being hit by a car, but otherwise apparently not seriously hurt. A doe stood in the wooded edge of the road. Cars drove by, occupants observing or oblivious. A bicyclist rode by. Stopped. Laid down the bike. Picked up a rock. Walked back…

Birds of a Feather...

Some birds flock. Some birds don’t. Several hummingbirds may appear at a feeder, but they are definitely not a flock. Robins flock in winter, but in breeding season form territorial pairs. Ditto swans. Starlings, however, are rarely seen singly, and the same applies to flamingos. Other species gather in large groups to roost at night (crows) or only when migrating (sandhill cranes).

Geese in "V" formation

In flight, being in groups has several benefits. Geese form lines diagonal to flight direction, sometimes a “V” formation with one bird in the lead and lines trailing on both sides, because the air disturbance coming off the lead bird’s wings enables the trailing bird to expend less energy.

When feeding in groups, one or more birds are always pausing to watch for predators, either the fox on the ground or the diving hawk. Warning sounds and sudden movement by these observers triggers mass evasion by the rest of the flock. In the air or on the ground, being in a group can also hinder a predator from targeting and pursuing one individual bird out of the flock.

Group behavior is seen in species other than birds. Fish school. Mammals form herds. There is a saying about being on a hike in bear country: “You don’t have to run faster than the bear to get away. You just have to run faster than the guy next to you.” Generalized to herd behavior, the best strategy against a predator is to put another individual between you and the predator. A grouping may be somewhat scattered to feed, but cluster inward when predators approach, as each individual tries to move to the center. If the grouping has a familial relationship, vulnerable young may be moved to the center while adults form a protective barrier. Think musk ox or elephants.  

A different reason for forming large groups is referred to as “predator satiation.” When prey appear suddenly and in large numbers, the probability of any one individual being killed by predators is reduced, the reason being that the predator population is low before the prey arrive and cannot increase fast enough to take advantage of the sudden influx of food. The sudden appearance of prey in great numbers can be from migration by massive numbers, or by near-synchronization of birth of young, or even skipping years. An extreme example of the last is the 17-year cicada

Painting of passenger pigeons, male on left (internet download)

Back to birds. We are some 120 years from one of the greatest species extinctions caused by Man – the end of passenger pigeons. This native North American species – larger and with a much longer tail than the non-native pigeons we now know disparagingly as ‘rats with wings’, numbered in the billions before the arrival of Europeans, and actually well into post-colonial times. Their food of choice was acorns and other tree nuts, but seeds of any plant were also consumed, as was fruit, berries and insects. Individual flocks of migrating birds numbered in the millions, and were described as darkening the sky when passing overhead. From an 1855 description, Columbus Ohio: “As the watchers stared, the hum increased to a mighty throbbing…Children screamed and ran for home. Women gathered their long skirts and hurried for the shelter of stores. Horses bolted. A few people mumbled frightened words…and several dropped on their knees and prayed.”

Roosting at night, the birds were so densely gathered as to break the limbs off trees, and in areas where they nested, droppings piled up a foot thick, poisoning ground plants, and in time, the nesting trees. The birds moved on.

Passenger pigeons, more than other flocking bird species, depended on predator satiation, and so were not able to adapt to human harvesting. The end came quickly. Circa mid-1800s, market hunters used shotguns, nets, whiskey-soaked corn and so on to bring birds to ground. Birds were plucked, gutted, cooked, salted and packed into barrels, to be shipped by railroad to the fast-growing cities of the Industrial Age. Their meat ended up in pigeon pie (think today’s meat pies). At the nesting sites, ground fires would be lit when the nestling squabs were nearing adult weight but not yet able to fly. The squabs would fall to the ground, stunned, to be picked up by hand. As flocks vanished from the usual places, telegraph messages would go out about newly found locations. Market hunters followed.

Locally, Henry David Thoreau’s journal from 1851 recounts a visit to a ‘pigeon-place’ where birds were lured in by trees for perching (live decoy birds tied to the branches), then netted. The last birds seen in the east were early 1890s, the last wild bird shot anywhere 1902, the last surviving bird died in a Cincinnati zoo, September 1, 1914. From billions to zero in fifty years.

Berries, Red; Birds, Red!

A robin’s red breast is an “honest signal” of mate attractiveness. In males, an indication of good health. In females, that she will product healthy eggs. While their black and brown feathers are colored by melanin, the same pigment that colors our skin and hair, the red is recycled from red berries. Late December is a great time to woods-walk in search of berries, obvious against winter’s white and dark tints. The species we see locally are winterberry, Japanese barberry, multiflora rose, burning bush and Oriental bittersweet.

Winterberry berries stay until robins or cedar waxwings
show up. Click on photos to enlarge.

Winterberry is a native, deciduous (leaf-shedding) relative of holly. Berries are round, clustering at branch tips. Cultivars are available from nurseries. Like holly, there are male and female plants, so at least one male is needed in a planting if the female plants are to have berries. Cardinals and other non-migrating birds don’t eat winterberries. In past times, when robins migrated south, these shrubs would retain the berries throughout the winter – hence the name. Now that flocks of robins stay the winter the berries rarely make it through January.

Japanese barberry is an invasive, naturalized from ornamental plantings. Sales now banned in Massachusetts. In wooded areas, barberry is a low, thorny shrub festooned with oval, red berries. It displaces native shrubs. Deer avoid eating it because of the thorns. Burning bush, also an escaped ornamental, is also banned in MA. It forms dense thickets three to nine feet tall, with small, rust-hued berries. Multiflora rose has modest white flowers in spring, branch-ending clusters of small, dark-red berries in fall. Together, these three can dominate a forest understory.

Winterberries covered with ice

Last/worst is Oriental bittersweet, a woody-stemmed, vining invasive that can blanket treetops with a haze of red/orange berries. It is a tree-killer. If there is any on your property, cut the stems as close to the ground as possible. While many bird species will consume multiflora rose and burning bush berries, winterberry and bittersweet are left for the robins (and the occasional flock of cedar waxwings). Examples of all five can be seen along the Assabet River Walk trail, which has signed entrances at Colbert Avenue and Concord Street. As a bonus, there is a decorated spruce tree 1/3 mile in from the Colbert Avenue end.

Back to birds. The addition of these invasive plants provides enough forage that some robins choose to not migrate south. Males especially, will remain here, to be closer to territory they intend to claim in the spring. These are not the plump and placid birds of summer. Rather, they move about in jittery flocks of 15 to 30 birds descending on winterberry like raucous starlings. Cardinals do not migrate and do not winter-flock, but they do eat other types of red berries and incorporate the color compounds into feathers (males more than females).

Robins do not always migrate, instead staying north as long as
there is food. This photo taken in 2011, winterberry bush.

From the plants’ perspective, birds eating berries is a means to making more plants. This explains why fruits and berries undergo veraison (turning color) when they do. Once the seeds are ready, the pulp becomes sweeter and the skin colorful, as a ‘please eat me’ signal. It is the reds, yellows and oranges of these skins – courtesy of compounds called carotenoids – that robins, cardinals, orioles, basically any bird of reddish feather, incorporate into feather color. Goldfinches get their yellow the same way. Insectivores such as red-headed woodpeckers get their share from plant compounds those insects ate.

Color matters only if an animal (or its predator) can see color. Insects, fish, amphibians, reptiles and birds see color, perhaps better than we do, including ultraviolet hues we cannot see at all. Birds are caught in a dilemma – be a brightly colored male to secure a mate, but then be at more risk of being seen by a predating bird or snake. Females, meanwhile, evolved more toward camouflage colorations that allow them to stay on the nest without being detected. Some species, such as mallard ducks, molt twice a year, the males brightening up for mating season, then going drab for the rest of the year.

Male Mallard duck in courting/mating colors.  

Most mammals have poor color vision or none at all (marine mammals), a theory being that during millions of years of early evolution mammals were mostly nocturnal, eyesight giving up color-detecting cone cells in favor of dim-light functioning rod cells. The old-world primates from whom hominids descended in effect re-invented color vision about 35 million years ago, the better to see ripened fruits and berries. Color blindness is far more common in men than women. One theory was that in the hunter-gatherer era, men needed to see movement while women were looking for ripe fruit, but the reality is that the genes coding for color vision are on the X chromosome, so that women who inherit one mutated X chromosome and one normal will not be afflicted, whereas men, who have only one X chromosome, are.  

Oh, and yes, a “dishonest signal” is lying, to either dissuade predators or fool potential mates. The tasty butterfly that has evolved a wing pattern and coloration similar to a different species that is distasteful is an example of Batesian mimicry. People who color their grey hair are just hoping for the best.

The genesis of this column was a 2009 observation that robins were no longer migrating south for the winter, to then become harbingers of spring

Norway Maple - Invasive Species

Norway maple as an urban and suburban tree is so well established that it feels counter-productive to proclaim that it is an invasive species. It is. The Commonwealth of Massachusetts prohibits the import, sale, trade or propagation of Norway maple trees. The ban dates to 2005, when the Massachusetts Invasive Plants Advisory Group proposed an initial list, last updated February 2017. From Mass.gov: “The Massachusetts Prohibited Plant List prohibits the importation, sale, and trade of plants determined to be invasive in Massachusetts. This ban also covers the purchase and distribution of these plants and related activities, and includes all cultivars, varieties and hybrids of the species listed.” The rules do not affect existing Norway maples already within the landscape, only bringing in or creating (from seed) new trees.

Norway maple cultivars offered by garden supply businesses
include varieties that have 'copper' or purple leaves. In this
photograph, the dark leaf came from a sun-exposed part of
the tree while the green leaf was from deep shade.

Worldwide, there are more than 100 species of maple trees (genus: Acer). Most are native to Asia. Here in New England the native species we see are red silver and sugar maple. In leaf, there is a nice mnemonic to remember which is which: each leaf has three lobes if r-e-d or five lobes if s-u-g-a-r. Leaves on silver maples – also known as swamp or water maples - have five lobes, but this species thrive best near or in wetlands, and so differentiates from sugar maple. Norway maple leaves also have five lobes, but differences in the leaf stem and bark help us tell the difference. For sugar maple, a snapped stem seeps clear, whereas for Norway maple, white. Sugar maples also have a more shaggy bark. In the fall, the native species color up in the orange to red spectrum, while Norway maple leaves lean toward yellow/orange.   

Three differences make Norway maple a yard bane compared to red or sugar maple. Seed production is more prolific, meaning that all summer one will be pulling seedlings out of garden beds. Branches are more likely to break in storms – due to weaker wood – and so more time playing pick-up-sticks. Roots are very close to the surface, to the point of stunting or stopping any grass, weed or groundcover plants underneath. As roots extend sideways roughly as wide as the crown of the tree above ground, this can create a large area of bare earth under the tree.     

The winged seeds are called ‘samaras’. Why? I don’t know.  The term describes all tree seeds that are incorporated into a flattened, papery casing so that they are easily windblown. Much like oaks and beech trees, heavy maple seed production occurs every two to three years. Interestingly, for sugar maples good sap yield in early spring presages a strong seed year, but then sap production is reduced for the spring following that strong seed year, suggesting that the trees have only so much carbohydrate reserves to either create seeds or promote growth. Samaras tend to detach from their stems on windy days, which promotes better dispersal.   

Norway maples have a long history in North America. Credible reports date the introduction to the mid-1700s for New England, perhaps a century later for the west coast.  During the mid-twentieth century urban and suburban plantings of Norway maple trees were common, especially as a replacement for the loss of American elms from Dutch elm disease. With adequate sunlight, adult trees can be 40-50 feet tall and equally wide. The species is tolerant of poor soil and a range of water conditions from drought to wet soil, but fares poorly as a sidewalk installation tree as it prefers to establish a wide, shallow root bed. Lifespan is short compared to native species. Yard, park and cemetery plantings done 50-70 years ago show their age in increased loss of large branches from storms followed by slow replacement growth.

As to why designated invasive in Massachusetts, seeds from suburban plantings are wind-blown into bordering forests. There, due to its shade-tolerant nature as a seedling and sapling, Norway maples out-compete native species. The dense canopy it creates combined with its shallow root system means that forest diversity declines. The loss of understory plants cascades into a less hospitable environment for insects and the animal species that prey on them.

Conservation agents for Massachusetts cities and towns may consider establishing an anti-invasive plants program, but the reality is that killing mature Norway maple trees – the most effective way to stop seed production – is lower on the list than addressing faster-growing/spreading invasive species such as Oriental bittersweet and Japanese knotweed.

Previous plant winners of this column's "Invasive Species of the Year" are in a September 2012 item at www.maynardlifeoutdoors.com. Future candidates include Japanese barberry, purple loosestrife…