Wednesday, August 26, 2015

Suburban Ravens in Massachusetts

EXTIRPATED: the condition of a species that ceases to exist in the chosen geographic area of study, though it still exists elsewhere, i.e., locally extinct. Often tinted with a meaning that incorporates a deliberate destruction and eradication of an evil presence.

For those with an attentive ear to bird calls, Maynard's summer has been host to a mystery which, depending on how you feel about scarily large black birds, is either a return of nature or a return of evil. Amongst the common "Kaws" of crows there has been the occasional deeper-voiced "Awk, Awk." First guess was that this was a crow with a sore throat, or perhaps a vocal dyslexia (Kaw versus Awk?). However, many sightings confirmed that what Maynard has is a resident pair of ravens, which this year successfully raised a family.

What's interesting here is that dogma on ravens states they are people averse. Most habitat maps show ravens in Alaska, Canada and down the spine of the Rocky Mountains, but in the east limited to northern parts of northern states. The reasons are three-fold. First, ravens prefer forests. As this part of Massachusetts became settled by European colonists the forests were cut to make space for farming, for housing, for industry and to provide firewood. Even unfarmable hilltops became sheep pasture.

Three exposures of one raven in flight (internet photo)
Second, ravens prefer not being shot. Past times, there were no hunting/shooting restrictions on crow and ravens. Both are known to damage crops, including pulling up seedling corn to eat the kernels. Both are carrion eaters, but ravens have been known to be more proactive, for example, raiding chicken coops for chicks and eggs, and killing newborn lambs. For good reasons, generations of ravens taught their offspring to stay far away from humans.

Third, ravens like to eat. Pre-colonial forests had been home to deer, elk and moose. Wolf kill and winter kill provided carcasses for these carrion feeders to dine on all winter, and of greater importance, hair to line nests and early spring food sources for their hatchlings. The recent explosive growth of the deer population contributes to a year-round food source, supplemented by scavenging road kill, nest robbing, and so on. Ravens will eat almost anything, including food left outside for pets and garbage from open-top dumpsters behind restaurants and food markets.

So, much akin to other extirpated species which have been returning to eastern Massachusetts - deer, turkey, beaver, bear - a decline of hunting combined with an expansion of preferred habitat (forests over farmers' fields) has led to a return of ravens. For birds, especially, the Migratory Bird Treaty Act made it "...illegal for anyone to take, possess, import, export, transport, sell, purchase, barter... any migratory bird, or the parts, nests, or eggs of such a bird except under the terms of a valid permit issued pursuant to Federal regulations." There is a hunting season for crows (and deer, and turkeys, and black bears), but not for ravens.

Ravens are wanderers but not migrators. An adult pair will defend a territory that can be ten miles in area, chasing away interlopers, including their own chicks from previous years. Younger birds, up to five years old, will gather to roost at night, or to take advantage of a food bonanza (dead deer) by day, but otherwise are opportunistic feeders and solo travelers.  

In conclusion, if ever you hear a bird call louder than any crow should be, look to the sky. The size difference is hard to perceive without a side-by-side, but ravens in flight glide more often compared to crows' flap, flap, flap. At wing ends, the primary feathers of a raven are splayed. What you are seeing is an extremely intelligent, playful, ruthless, long-lived species, known throughout history as a battlefield follower, gallows haunter, trickster, thief and oft-used symbol or omen of evil.

In 2014 Chris Renna posted a video of ravens hanging out in Maynard, some of it on rooftops of mill buildings. See YouTube (search Ravens Maynard). A 2015 video of ravens raising a family at/on the Wellesley College Science Center is posted at http://www.wellesley.edu/ravencam. Mind of the Raven, by Bernd Heinrich, provides great detail on raven intelligence and lifestyle.

Cornell University has audio at http://www.allaboutbirds.org/guide/Common_Raven/sounds.

Beak to tail-tip, ravens are 50-60% larger than crows, and weigh twice as much. The head and neck is larger in proportion to the rest of the body. In flight, a crow's tail is straight across the back end, while a raven's widens, then narrows. Both can walk or hop (many smaller birds only hop).

As to why we sometimes see small birds in flight chasing and harassing much larger birds, that is nest defense. The smaller birds are agile enough to fly above/behind the larger bird, then dive in for a peck or two. On a different scale, in Alaska, ravens have been known to harass bald eagles in the air, and on the ground, when feeding at the same carcass (left behind by wolves or polar bear), to sneak up and pull an eagle's tail feather.   

1 comment:

  1. Just heard and saw my first pair - in Medfield. Very surprised to have spotted them. Thought they might be turkey vultures, they were so large in flight, and so loud. Photographed one, and when I zoomed in, bingo! Raven. Very cool. :)

    ReplyDelete