Rarely have I captured a Great Blue Heron poised to strike, as this one is. It had not been fishing here, one of its favored spots, for the past few days. It looked a mite hungry.
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There had been a good many boats on the water during that time; they almost certainly kept the big bird away. That isn’t a knock on boaters, just a reflection of how shy this great bird is. I’ve only to open a window, and it’ll fly off. Just a single boat in sight will keep it away. This was one of those hot, humid days in July that kept boaters at home. Of course, I’m reporting only what I see here in the southern end of the pond. The boat ramp is at the southern tip, leading me to think there may be more boats down here, and fewer in the far northern end, where the Great Blues are also seen, and where they may seek refuge when boats are present here.

In the past, I often saw three or more Great Blues on the pond at one time. The photo of four friends, just below, I took on January 12, 2007 with my very first digital camera, a little point-and-shoot. In years past, I saw even greater numbers of Double-crested Cormorants. I captured a small flock of them in the water on May 20, 2011, swimming partly submerged, as they are wont to do. The photo is near the bottom of the post.

The virtual disappearance of the Great Blues and many other regulars — gulls, cormorants, and Green Herons — is almost certainly due to the mass die-off in March 2012 of Bluegills. These small sunfish were a basic food source. Their loss has been devastating. The gulls used to congregate here by the dozens, their plaintive calls carried by the currents, a reassuring reminder of their graceful presence. Now, I’m lucky to see a single gull, cormorant or Great Blue Heron on any one day. It’s a bleak prospect out there beyond my window.

I’ve seen no Green Herons so far this year, but I did photograph several last year. The waterfowl are still with us, of course — the elegant Mute Swan pair, the honking, cantankerous Canada Geese, and about a dozen, peaceable Mallards, all thriving, of course, on a vegetarian diet. None of them seem to be bothered by the boats, unless of course, they have young’uns in tow.

There’s been a sharp uptick in boating since the new boat ramp was built last year. The Great Blues, as I said, are shy of the boats, but the cormorants and gulls don’t seem to take offense. One can never be sure, though. A few boats in normal times may be harmless enough, but many boats, and coming after the loss of a major food source, may further stress the birds, hastening their departure. I’m not picking on the boats; they’re just a visible form of human intervention. Other examples are rampant.

The larger point is that such impacts can be cumulative; weakness resulting from one can increase vulnerability to others, with stresses on the system mounting. A pond’s ecosystem by its nature is a delicate one; it does not have unlimited capacity to take everything we can throw at it. If we wish to preserve the pond near to its natural state, we must be aware of, and allow for its limitations.

Such impacts are not only cumulative, but can be linked in a chain of causality. A case in point is the pond’s silted outlet channel. It had been partly silted for decades, but was further filled in by the great floods of March 2010. Such a blockage, it’s not unreasonable to assume, may slow natural flushing of the pond’s water, furthering the build-up of 1) toxins, or 2) decaying organic matter that depletes dissolved oxygen. Either scenario could explain the mass fish die-off of 2012. Last, but not least, destructive floods are now far more likely, with the outlet so heavily silted. The pond is like a bathtub with a stopper in the drain.

The good news is that the Mayor has asked the Consolidated Public Works Department to look into the cleaning and repairing of the outlet channel — but she has yet to commit funds for it. I do believe our elected officials understand the critical importance of this project, with its dual benefits for flood control and the pond’s ecosystem. It’s simply a matter of priorities. If enough people speak to their city councilors, or to the mayor, herself, it will in time rise to the level of action.

A final note on the vanished water birds: Over time, Purple Loosestrife, an invasive species, has crowded out native plants in several areas along the shore, and almost entirely in the great northwestern marsh. The vast loosestrife monoculture of the marsh deprives many birds of the feeding and nesting areas on which they depend. Here’s what Wikipedia says:

Purple Loosestrife infestations result in dramatic disruption in water flow in rivers and canals, and a sharp decline in biological diversity as native food and cover plant species, notably cattails, are completely crowded out, and the life cycles of organisms from waterfowl to amphibians to algae are affected.

Biocontrol of loosestrife is the only method that has proven effective, using beetles that attack the plant. Sadly, a state program supporting such efforts has ended. For individuals or organizations wishing to mount a beetle control program of their own, the state now provides limited technical advice. A beetle program, we’re told, can be a good classroom project, one that’s not costly to run.

The pond is valued as a place where residents commune with nature. It’s also home to many diverse creatures, from tiny, single-celled organisms to insects, fish, frogs, turtles, mollusks, birds, muskrats, and countless plant species. Therein lies its appeal, but also its challenge: Can we strike a balance between our use of the pond for recreation, and the health of its complex ecosystem?

Past, strenuous efforts have succeeded in saving the pond, but husbandry, like housework, never ends. Its now time to renew our stewardship. If we fail to act, we may diminish the very things about the pond that we value, and that draw us to it. Some day, the heron we see on the pond could be the last. The silted outlet and the loosestrife are the low-hanging fruit; they are the places to start.

Summing up: The principle that wildlife populations fluctuate with food supply is widely recognized. The real issue is why the food supply — in this case, the Bluegill sunfish — died off in the first place. Fish kills due to natural oxygen depletion (anoxia), though common other times of year, are almost unheard of in the spring, according to MassWildlife. When large die-offs do occur in the spring some human complicity is assumed. I’ve posited stagnant water from a silted outlet channel, but I freely acknowledge there could be other causes, either alternate or contributory. Adding to the mystery is why the birds began to come back a few months after the March 2012 die-off, only to disappear again. In the past, fish stocks have recovered after mass die-offs. Can we always take it for granted? In time, perhaps, the City’s new water testing program will shed some light on these questions.
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Related: The Last Heron II*, Testing the Water*, Purple Loosestrife, Mono Lake*, Dead Fish*, Snatching Gulls*, and
The Great Flood.

 

6 Responses to The Last Heron*

  1. Marc Rudnick says:

    Great food for thought as usual, Ron. I couldn’t agree more that human activity can reduce the local population of many species, and that we should be vigilant in our stewardship of the pond. But your “science” fits a bit too conveniently with your conclusions: You say: “The virtual disappearance of the Great Blues and many other regulars — gulls, cormorants, and Green Herons — is almost certainly due to the mass die-off in March 2012 of Bluegills.” This is a stretch in my view. Great Blues have not virtually disappeared — their numbers here are always few — 2 or 3 regulars who strongly defend their foraging territory, which number swells to quite a few more when migrants pass through. I see at least one almost every day and often two this summer. Regardless, GBH’s don’t depend on bluegill. Their diets are quite varied, including dragonflies and grasshoppers, aquatic insects, snakes & reptiles, salamanders and frogs, rodents, crayfish, crabs & shellfish. Gulls eat practically anything. Cormorants are more dependent on fish, but without actually keeping records, it is hard to make a case that any of these birds are present in numbers outside of their typical fluctuations. Don’t forget that we see barely half of the Hardy Pond ecosystem and the herons and cormorants forage in the swamps and marshes as much as in the open water. My observations (non-scientific) this year interestingly differ from Hardy Pond Gramdma’s: I thought the goose population is higher this year, i’ve seen almost no goldfinches, but plenty of blue-jays. (and way more cardinals – i agree!)

    When I interviewed experts about the fish kill, as many theorized weather as the culprit as posited local human impacts. Without good scientific study, the mysteries of nature remain mysteries. Like you, Ron, I hope the testing gives us a good basis for demanding improvements to the brook and the outlet structure, and for understanding phenomena like the fish-kills.

    There’s my nit-pik, my friend. I salute your incredible devotion to Hardy Pond – thanks as always for the thoughts and pix. =marc

    For Ron’s reply to this comment, see The Last Heron II*.

  2. Hardy Pond Grandma says:

    Thanks Ron. Nice summary of our valuable pond and conditions and great photography as usual. We saw far fewer water-fowl babies this year. I am not sad about seeing fewer Canada geese! I’ve seen more cardinals this year, gold-finches, wood-peckers and fewer blue-jays, and no mourning doves. I saw a craw-fish among the lily pads at one end of my shore-line. I do have gulls, not as many as before. I do still see the heron perched right behind my row-boat, usually very early in the morning.

    I hand pull the purple strife along my shore line, as well as the poison ivy on the edges, one needs to start very early in Spring. This year I was not able to keep up.

  3. Dede Reade says:

    Good stuff Ron. I’m most particularly interested in the loostrife situation. The Hardy Pond Association has had a number of conversations in our meeting about the beetle program. It would be great if someone (perhaps you?) would like to head up a committee that could look into it in more depth, learn more about it and see if it’s something we might want to consider more seriously. Interested?

    Dede

    • Ron Cohen says:

      Thanks, Dede. At my age, this writing has to be my contribution. There must be some young folks who’ll take on the loosestrife. How about a high school science teacher who’ll make it a classroom project?

  4. Robin Mirollo says:

    Thanks for telling it like it is. Signed, the last Great Heron

  5. Jim Fett says:

    Excellent photos as usual Ron. And a considered discussion of the issues facing the pond that include balancing the wildlife ecosystem with the human use of this wonderful resource. Hopefully ‘we can all get along’!

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