Megunticook Watershed Association

Education, Preservation. Join today.

Critter Facts

Great Blue Heron

In the wetland, the misty wetland, the heron hunts, day and night. Probably not as catchy as song lyrics as those about the mighty jungle and the sleeping lion, and the heron’s voice itself is anything but melodic, but a great blue heron standing stock still at the edge of a lake or pond completes a scene of quiet beauty. Maine is not a state with too many commonly seen heron species. The great blue heron, the largest and frequently the most typically spotted of all herons in many places, is a notable visitor to the watershed especially as the summer progresses and more shallow shoreline is revealed.

With a height of nearly four feet and, when flying, a wingspan of six feet, this is a large bird but often you have to really be looking carefully because its gray and white plumage can blend in well with the colors along the water’s edge. And of course, it rarely moves when it’s fishing, and then to rapidly strike at prey with its long, pointy bill. This weapons-grade appendage has been clocked at 90 miles per hour! In the air, it coils its long neck back toward its body but with legs and feet outstretched and slow, lumbering flight, it is readily distinguished between other large birds such as ospreys and eagles and also sandhill cranes which do live in parts of Maine.

On the lake, a hunting heron can be spotted on the bog side of aptly-named Bog Bridge, especially in late summer when they disperse from their breeding areas. You are not likely to hear its raspy croaking call which is typically heard more on their breeding grounds, a communal rookery on an island or other isolated watery environment. To hear recordings please go to https://www.allaboutbirds.org/guide/Great_Blue_Heron/sounds) What are they hunting? Almost anything, from frogs to fish, from snakes to small birds, from mice to mayflies. Larger fish can actually be impaled on the beak before being subdued by shaking and then swallowed.  Their exceptional eyesight permits hunting even in darkness, something that has been noted by
volunteers for the on-going initiative tracking individuals using transmitters. You can follow these Maine birds in their southward migration as well as see some great photos at this Facebook site https://www.facebook.com/maineheron/
Usually not thought to be a bird species of concern, in Maine recently they are in the sights and talons – of bald eagles.  Especially at the breeding colonies, the appearance of an eagle can mean the end of the colony. The herons leave and in many cases do not come back. Eagles’ traditional food sources – fish, primarily ocean fish – are in decline, so the birds are feeding on
alternate prey.  Alas, great blue herons are on that growing list.
Keep your eye out for herons late into the fall when they still might haunt the quiet gray waters that are not ice-bound. Leaves may be down, emergent vegetation brown, and the wetland is otherwise in winter mode. It’s always nice to be reminded of our summer residents and look forward to returning green and blue seasons by the lake!
For more information: http://www.freepressonline.com/Content/Columnists/Birding-with-Don-Reimer/Article/Herons-and-Egrets-/50/100/47718
https://www.allaboutbirds.org/guide/Great_Blue_Heron/lifehistory
http://georgesoutdoornews.bangordailynews.com/2016/06/29/conservation/bald-eagles-are-killing-maines-great-blue-herons/
http://www.maine.gov/wordpress/ifwheron/tracking-project/

Spider!!!

Dolomedes_tenebrosus_1_PEM

Dolomedes probably means nothing to many people, myself included, and it has nothing to do with the very similar dolomades, a Greek stuffed grape leaf delicacy. Not even close. However, mention dock spider and, oh yes, that does come in loud and clear. Docky, as the spider of the year is inevitably named in our household – and invariably there is at least one that stakes out a territory on our dock – invokes fear and trepidation for almost anyone dangling legs in the water, gripping the swim ladder, or sitting in proximity to almost any nook or cranny around the edges of the dock. So here are some details that might help dissipate the fear if not the loathing.

Dolomedes is the genus name for this large spider that frequents docks, often seen with outstretched legs which make it seem even bigger than it is (and that is pretty darn big -up to 3 inches or so including appendages). Also known as fishing spiders, they do not spin traditional webs but rather detect surface disturbances on the water and make speedy forays to grab prey nearby. Some spiders are large enough and presumably speedy enough to trap small fish but insects, not dangling feet, are the usual food items, thankfully. They do inject venom to subdue the prey which is grabbed at first by claw-like structures on the spider’s legs. Fascinatingly, they also can dive beneath the surface and, surrounded by a layer of air, can even breathe while underwater. Their hairs repel water so they remain dry, and because of this air dry-suit, are very buoyant so they pop to the surface if they don’t find something to hold onto while submerged. Most of their hunting is done at night and the ability to sense vibrations outweighs any visible means of finding their dinner. You would think that with 8 eyes, 4 in each of two rows, their sight would be a primary hunting tool but not so. These vibration detectors also function as an early warning system for any predator such as a fish that might enjoy a spider meal! Are you less scared yet?

Campbell_20110922_Maine_1000951

One Dock Spider eating another

If not, here is more to add to the notion that knowledge is a great antidote to fear. There are nine species in North America. In Maine, two species can lurk, if you must, or at least set up shop on a waterside structure – Dolomedes tenebrosus, the dark fishing spider, which also can be found away from water, and D. triton, the six spotted fishing spider. Next time you see one, get a grip and try to see the spots. Actually, D. triton seems to have lines along its sides whereas D. tenebrosus is just simply dark. This later species exhibits a rather large discrepancy between the size of the female and the male, which is less than 1/2 the size of the female. Alas, males do not survive mating although it’s not from being eaten. Deemed ‘self-sacrifice’ in one on-line article, no other details were revealed.

Often in close proximity to the large female dock spider will be a web nest with tiny spiderlets, hundreds are them, (actually an egg sac can hold about 1,000, another amazing fact) that twitch in unison when the webbing is disturbed. Another common name for this group of spiders is the nursery web spider, a reference to this behavior. The female, exhibiting true maternal behavior, guards them after she attaches the hatchlings in their web to usually something inconvenient (for us) like the arm of a chair, the rope that wraps around a dock cleat or even the steering wheel of a boat. It is unclear to me what happens to all the baby spiders but they seem to decrease in number over time, maybe eaten by other predators or even each other? Survivors hibernate as immature adults in protected spots such as beneath rocks or behind bark of tree. In the spring, after a final molt, they mate and females carry their egg mass around until the spiderlings hatch. Tiny, they are cute; really they are!

Campbell_20100824_Maine_5713

Mama spider tending her eggs

Supposedly the venom of these spiders is not particularly strong or dangerous. We as a species seem hypersensitive to the idea of spiders but they are extremely important in the balance of nature, in their role as predator. Try to just let them alone, let the nests persist. They are interesting to watch, add to all the wonders we call life and probably very few survive. Otherwise, well, let’s just say that we would be even more likely to post a sign on the ramp to the dock that reads “Beware of Spiders.”

Reference: Insects: Their Natural History and Diversity by Stephen A. Marshall
Dolomedes, Wikipedia, the free encyclopedia, https://en.wikipedia.org/wiki/ Dolomedes
Genus Dolomedes – Fishing Spiders, http://bugguide.net/node/view/1985
Maine spiders – http://www.spiders.us/species/filter/maine/
Canada’s Largest Spider – http://arthropodecology.com/2012/08/13/canadas- largest-spider-sittin-on-the-dock-of-the-bay/

 

Mayflies

St. Peter welcomed a new arrival at the gates of heaven. He said, “Congratulations, you have been selected to be reincarnated as a mayfly. Have a nice day!”

If people other than fly fishermen know anything about mayflies, it is the fact that they live very short lives as an adult, usually just a day or two at most. There is even a species whose females live for a brief five minutes, not time enough for a cup of coffee.

Mayflies, insects that are inspiration for many fly-fishing lures, are certainly seen in other months as well in Maine. Another commonly-known mayfly factoid is that the adults, often found perching on screens or other vertical surfaces, do not eat during that brief existence which is primarily spent flying, doing a nuptial dance in a swarm that ascends and descends, mating, and, in the case of the females, laying eggs. They are truly ephemeral, as their appropriately-named order, Ephemeroptera, reflects, at least in their adult phase. Often they emerge at once in great numbers from waterways such as streams or rivers or lakes. Last year, one cloud of hatching mayflies could be observed on radar over the Mississippi River in Wisconsin.

The immature mayflies, called nymphs or naiads, are aquatic, complete with long tails and gills along their abdomen. Depending on the species (according to the Mayfly Central website there are over 650 in N. America), mayfly nymphs are aquatic for a couple of months to as long as a couple of years before becoming airborne adults. They eat algae or detritus or, in a few cases, they are predatory. Unique among insects, and an indication of how ancient a type of insect they are, they shed their skin anywhere from ten to fifty times before they molt to a winged pre-adult form that is called a subimago. This first aerial form which fly fishermen call the “dun,” ( the basis for many a fly-fishing fly) and which might last anywhere from a few minutes to two days, resembles the adult but is a poor flier, has cloudy wings and is not fully sexually mature. Trout are particularly fond of this more helpless form; particularly just as it emerges and can not yet fly off the water. A further molting transforms this stage to the adult, or imago.

Mayflies are quite important in ecosystems for a number of reasons. Since the larvae are sensitive to pollution such as sewage, pesticides and industrial runoff, their presence (as that of caddisflies and stoneflies) is an important indication of a healthy body of water. Because they feed on organic matter, they can be helpful in removing nitrogen and phosphorus from the water as they become terrestrial as adults. Larvae provide a source of food for other aquatic insects as well as fish and up the food chain. The adults are eaten by birds, bats and predatory insects such as dragonflies.

A bit (or lots of bits ) of history: in the 1940s and 50s, a type of mayfly known locally as shadflies emerged from Lake Erie in such numbers that they had to use snowplows to remove them from bridges and roadways. The dead insects reeked as they rotted in huge numbers. By the early 1960s, this bounteous and beneficial insect dwindled due to pollution. Now, however, the population has increased so that once again they are able to thrive and emerge in ‘snowstorm-like’ numbers.

Maine has two mayflies on the state endangered species list (the Tomah Mayfly and Roaring Brook Mayfly, neither of which is found in Knox County) but according to Hatch Guide for New England Streams, by Tom Ames, Jr. the state has more mayfly species than any other state – 162.

Here’s a bunch of pictures of a mayfly dun molting to a spinner:

http://www.troutnut.com/article/10/pictures-of-mayfly-dun-molting-to-spinner