Standing in the St Lawrence, a short distance downriver from Kring Point State Park, Ironsides Island is an impressive sight. Its high granite bluff shoreline is stained by the rust covered lichen that gives it the name Ironsides. Except for two locations on the south side, landing is a difficult task that requires climbing a steep rocky eroding path, to reach the plateau forming the island’s crest. Donated to The Nature Conservancy in the early 1960s, landings are prohibited between April and October. The island is a registered National Natural Landmark where both state and federal regulation applies.
The primary reason for these restrictions was the Great Blue Heron colony that developed on the island beginning around 1960. This assemblage grew from a few nests, to over 1400, at the turn of this century. Birds from this colony at the peak of the nesting season, probably commuted daily from from Clayton to Ogdensburg, In addition, many sought food, miles inland, up the creeks flowing into the River and undoubtedly hunted the Indian River Lakes Region as well. The ecological impacts of birds, from this avian metropolis, were felt far and wide.
The story of the Ironsides’ Great Blue Heron Colony is fairly typical for colonial herons and some other waterbirds in our region. The colony develops and prospers in the early years, growing as young raised there return to breed. Augmented by other individuals attracted to the vibrant scene, the growth rate accelerates. Herons and other colonial waterbirds are social animals while breeding, finding many reproductive advantages in nesting in large colonies. Bigger is better from the standpoint of reduced predation potential for an individual. Also social stimulation from other pairs’ reproductive cycle activities enhances likelihood of success of any given pair.
As with population growth and concentration of most living organisms, success brings problems as the species approaches carrying capacity limits, imposed by available resources. In the case of the Ironsides’ colony, the initial signs of trouble began appearing in the mid-1980s. Thickly covered with a mature mixed forest, when the colony was established, the island was showing wear and tear from its large, long-legged summer residents. Since herons never have developed sewage systems, excreta are just cast over the side of the nest. This material has a very high nitrogen content that burns and eventually kills the nest tree. Over a period of years, the loss of many trees in this manner began to open up the forest on the island, resulting in significant ecological changes. Nesting songbird populations changed, and first-time breeding herons had trouble finding nest sites.
Decreased available nest sites, combined with increased population levels undoubtedly resulted in more conflicts between pairs. Also, as the colony grew, it is likely adults had to commute farther for food. It’s probable that all of these factors were probably impacting reproductive success by at least the mid-1990s. The rate of colony growth was slowing, and it is likely natural decline would have begun in this century, anyway. In the first year of the new century, 2001, another event changed Ironsides dramatically. A pair of raccoons reached the island, probably by crossing the ice. Ironsides had been predator-free during the colonies history and the establishment of climbing mammals had a catastrophic effect. The colony was abandoned the first year and when some birds returned the next spring, in 2002, they did not remain for long. For the moment, the saga of Great Blue Heron nesting on Ironsides Island was over.
Despite the removal of the raccoons by USDA, at the request of The Nature Conservancy, the herons have not returned. It is likely the condition of the island habitat is no longer attractive to pioneering birds. Waterbirds are homebody’s, with a strong attraction to their nesting site. Ornithologists call this “site tenacity” meaning that birds remain in a nesting area until conditions deteriorate to an unsuitable level. Unlike other waterbirds, such as Common Tern, where humans have limited their habitat availability, there seems to be adequate nesting sites for Great Blues locally. Since the abandonment of Ironsides there have been smaller colonies on Wolfe and Carleton Islands and other places where Ironsides birds and their descendants likely settled. Overall, the population of Great Blue Herons, in our region, appears to be fairly stable. The collapse of the Ironsides mega-colony probably just rearranged the distribution of this species in our region.
Personally, I miss this heron megalopolis because it was such an accessible obvious part of the scene in that part of the River. One could sit off-shore in a boat and enjoy watching the behavior of residents of this heron city. As part of survey teams, conducting an annual census, I was privileged to witness the everyday life of these birds up-close and personal. From unfortunate dead young birds that had fallen from nests, and the aroma of excreta mixing with that of death, we observed nature in the raw. Though not as Disney might portray it, it reminded me when a young biologist, that the natural world is an unforgiving place where serious mistakes aren’t tolerated. The young heron that is pushed or falls from the nest or chokes on too large a fish doesn’t get to call 911 and will not contribute to the species gene pool.
The current fauna of Ironsides Island today is very different from that of four plus decades ago. The heron colony and many of the forest’s interior songbirds are gone. Instead, Osprey and Common Raven are present, along with successional birds like Common Yellowthroat. Already young trees are rising from the extremely well fertilized plateau top. The rich understory of vascular plants, composed of a wide variety of types, has developed in the last decade and a half. This is providing a dynamic nursery for the next generation of Ironsides forest. Nature’s cycle has begun again, and depending on what we do as the planet’s dominate organism, Great Blue Herons may once again return to nest on Ironsides.
By Gerry Smith
Gerry Smith is a senior Ornithologist, Avian Ecologist and Conservationist working to Preserve bird populations in Northern New York.
Editor’s Note: This editor is both pleased and appreciative to Gerry Smith for taking the time to help us understand more about nature in the islands. You can read his past articles here.