Wednesday, December 26, 2018

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

Thursday, December 13, 2018

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 “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 Future candidates include Japanese barberry, purple loosestrife…

Wednesday, December 5, 2018

Eastern Coyotes have Wolf Genes

One hundred years ago Massachusetts had no wolves - they had been hunted to local extinction. Coyotes were not here yet. Their natural territory was mostly west of the Mississippi River. During the middle of the last century coyotes started appearing in upstate New York, and as time went on spread to the New England states. Today, most town woods, parks and golf courses have coyotes in residence. Sightings are common within Boston city limits. Estimates are that there are 5,000 to 10,000 coyotes in Massachusetts. But are these western coyotes migrating east, or something else entirely?

Eastern coyote, Mt. Auburn Cemetery, Cambridge, MA (internet download)
The answer – something else. Anyone who has visited the southwest knows the coyote as a 25-35 pound predator and scavenger more comfortable in open country than woodlands. What we have locally are coyotes, more on the order of 35-55 pounds. Their coats are thicker. Their jaws are wider and stronger. Typical coat color is a grizzled gray but can vary from creamy blonde to red or nearly solid black – the same color range seen in wolves. In the vacuum left by the absence of wolves, they are the apex predator. Although much of what they eat is still small game and fresh roadkill, they are successful hunters of deer.

Grey wolf, average adult weight 90 pounds (internet download)
As it turns out, our local coyotes are coyote-wolf hybrids. DNA analysis confirms that coyotes migrated from the mid-west northward into Ontario and Quebec 80-100 years ago, where they mated with remnant populations of red wolves. Small numbers of these coy-wolves crossed the St. Lawrence Seaway to New York, either during winter ice-over, or perhaps on bridges. This fast-spreading, east-spreading population has been referred to as a “hybrid swarm.” Purebred “western” coyotes also moved east across Ohio and western Pennsylvania, but more slowly, and without the size change. Earlier arguments that what we see in the east are coyote-dog hybrids does not stand up to examination. Genetically, the animals are about 30 percent wolf, perhaps with a trace of dog genes. Coyotes and wolves mate in late winter for spring litters, plus males actively partake in feeding and caring of pups – two traits not seen in dogs.

Western coyote, average weight 25-35 pounds (internet download)
What does it mean that wolves, in the form of these coy-wolves, are in New England?  Hunting pressure by coy-wolves is beginning to slow the runaway deer population. Ditto the Canada geese population, although purebred coyotes manage that just as well in the midwest. Pressure is also increased on the feral cat population, and probably wild turkey, rabbits, opossums, woodchucks, etc. In suburban and urban areas the culprit tipping over garbage cans is more likely to be coyotes than raccoons.

Being a good neighbor to your local coy-wolf means not putting food outside for your pets. Or for that matter, your pets. Letting a cat out for the night is bad odds for getting that cat back in the morning. Walk your dog on a leash, especially in the woods. At home, a five-foot fenced yard should be enough to protect your pets, chickens, and other animals. Coyotes and coy-wolves are less adverse to living near human habitat than pure wolves, but they still tend to be shy. Although preferred hunting time is late evening and early morning, a coyote hanging out in broad daylight is not necessarily a sick or rabid animal. Still, peace of mind recommends reporting to the police, who will forward the information to an animal control officer. A recent item in the Stow police blotter had an officer reporting to a daytime coyote sighting, and chasing it away by throwing snowballs.

Grey fox, average weight ~ 10 pounds
Note long tail relative to body size
Click on photos to enlarge
Winter coyote sightings will usually be of individual animals. In spring, coyotes pair up for mating, and then raising the pups. From mid-summer into fall sightings can include one or both parents with the pups along for hunting lessons. By fall the family unit can resemble a wolfpack, as the youngsters are nearly adult size. Dispersal occurs in late fall, with the now-adult animals wandering many miles to find a territory not already claimed by a mated pair, and then find a mate. More people hear the yipping of coyotes than ever see one.   

Jonathan G. Way has spent years studying coyotes in eastern Massachusetts and elsewhere. His book, Surburban Howls, is a great read. He is trying to establish a no-hunting, coy-wolf wildlife refuge on Cape Cod. He also operates as a very informative website.