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Restoring Nesting Habitat for Common Terns at the Niagara Project

Restoration efforts agreed to during Federal Energy Regulatory Commission relicensing of the 2,441-MW Niagara project have doubled the number of common tern nests in the area around the project, which is owned and operated by the New York Power Authority.

By Stephen Schoenwiesner, Edward Alkiewicz, Lee Harper and Morris Perot

Restoration efforts for the common tern, implemented as a result of the New York Power Authority's Federal Energy Regulatory Commission relicensing of its Niagara Power Project, are the largest and most successful of their kind in the Great Lakes and northeast U.S. The common tern is listed as threatened under the Endangered Species Act. With almost 1,900 nests in the spring 2011 peak nesting count - compared with fewer than 500 before the project began a few short years ago - increasing numbers of nests and improving tern chick survival are among the benchmarks for this success. The unlikely, yet simple, combination of historic nautical structures with industrial materials such as gravel and fencing have created a safe, comfortable and popular haven for the common tern to thrive.

NYPA's 2,441-MW Niagara project, the largest producer of electric power in New York State, was relicensed in 2007 for 50 years by FERC. This extraordinary facility was constructed in 1961 at Lewiston, N.Y., near Niagara Falls, to help restore a critical supply of low-cost hydroelectric power to the Niagara Frontier region. Much of that power was lost when a rockslide in the gorge below Niagara Falls destroyed about two-thirds of the 365-MW Schoellkopf Power Station in 1956.

During the seven-year process leading to the relicensing, more than 100 stakeholders - including NYPA, its regional customers, state and federal resource agencies, Native American tribes, non-governmental organizations, local officials and other interested parties - scoped out a wide range of ecological, recreational and economic issues to be addressed. Among the ecological issues identified was the opportunity to provide additional habitat for important fish and wildlife species in the highly industrialized Buffalo/Niagara corridor. As part of the ultimate settlement agreement reached among the relicensing stakeholders, NYPA agreed to design and install a set of eight Habitat Improvement Projects (HIP) for species including the common tern.

The desire to enhance the quality and extent of nesting habitat for the common tern was of concern to all the stakeholders, but especially to the New York State Department of Environmental Conservation. In fact, Connie Adams, senior wildlife biologist with DEC, notes, "Through their Habitat Improvement Project, NYPA is improving and creating nesting habitat for terns on the Niagara Frontier, and nothing is more important to overall tern population success than this habitat improvement."

Adams is speaking about NYPA's recent completion of a Common Tern Habitat Improvement Project at four sites on large, concrete breakwaters protecting Buffalo Harbor, totaling about 10,500 square feet of improved nesting area. Figure 1 shows the location of the habitat improvement work. Beginning with an initial prototype enhancement, the number of nests on the breakwaters increased 81% (from 487 in 2008 to 882 in 2010). The increase is likely the result of birds moving from less-suitable, barren concrete areas to the newly installed nesting habitat comprised of pea-sized gravel substrate enhanced with driftwood logs and plywood chick shelters.

Although common tern habitat improvement opportunities were identified at locations throughout the upper river, the existing breakwaters in Buffalo Harbor, at the head of the Niagara River, presented the most viable conditions for success, with the greatest cost-efficiency. The immediate use of the new habitat by significant numbers of terns and the greater-than-expected chick survival rate has validated the selection of these breakwaters as the site for this HIP.

Project area

The Niagara River is the natural outlet for Lake Erie and is a 36-mile-long connection to Lake Ontario. The difference in elevation between the two lakes is about 322 feet, with the largest drop in elevation occurring at Niagara Falls. The falls roughly divide the river into upper and lower sections, which have significantly different environments. The upper river is wider and shallower, consisting of gently sloping shorelines. The lower river is a severe environment consisting of fast-flowing, deep rapids and the steep shorelines of the Niagara Gorge.

The water intakes for the Niagara Power Project are in the upper river, just above Niagara Falls, where water is diverted via conduits under the city of Niagara Falls to the Robert Moses Niagara Power Plant in Lewiston. An area above the intakes is known as the Grass Island Pool and forms the impoundment for the project. Because of the nature of the two distinct environments comprising the upper and lower sections of the river and the proximity of NYPA operations, the stakeholders decided during the relicensing process to focus habitat improvement activities in the upper river where conditions were more amenable to habitat modification.

Common tern biology and nesting behavior

In New York, the common tern (Sterna hirundo) nests in colonies on Lake Erie, the Niagara River, Oneida Lake, Lake Ontario and the St. Lawrence River. In these areas, the number of terns and the amount of nesting habitat for terns has declined dramatically over the past 50 years. The tern is listed as either endangered or threatened in every state of the Great Lakes region. Most terns from this region winter in the Caribbean or Central or South America. Terns, banded as chicks in New York, have been captured alive, and subsequently released, as far south as Brazil, which is almost 5,000 miles from the site where they were born.

Adult terns are about 14 inches long, with a 30-inch wingspan. They are graceful fliers as they dive into the water for minnows. Terns nest in May and June and generally lay two or three eggs. Tern chicks hatch in June and grow quickly. They are capable of flight after about three to four weeks and quickly learn to catch minnows on their own. Once old enough to breed at age 3, terns migrate back to their natal colony to mate and nest. The average age of a breeding tern in New York is 7 years old, and they have a life expectancy exceeding 25 years.

Terns born in Buffalo Harbor likely return to Buffalo or nearby areas to breed. There is little or no movement of adults between the Great Lakes colonies and colonies on the other coasts of New York, New England or elsewhere.

Nesting populations of common terns have been monitored almost annually by DEC since the mid-1980s. Since 1986, common terns have nested at 13 sites in the Niagara Frontier covering eastern Lake Erie, the upper Niagara River and Buffalo Harbor. These sites have included breakwaters and lighthouses, potable water intake structures, power tower cribs, and islands associated with water control structures for generating hydroelectric power. Since 2000, terns have nested at nine of these sites, having been displaced from four nesting sites by gulls and cormorants.

"Terns are a threatened species in New York largely due to loss of nesting habitat to the more aggressive ring-billed gull, degradation of existing habitat or displacement by human activity," says Adams of DEC.

Although common terns are found at many locations across the Niagara Frontier, the majority of the tern population nests on the Buffalo Harbor breakwaters, which are part of a navigation project maintained by the U.S. Army Corps of Engineers. The Corps became a project partner early in the process by allowing the use of its structures for nesting habitat improvement. The breakwaters are large, multi-level structures of concrete and large armor stone designed to protect Buffalo Harbor from the effects of severe storms on Lake Erie.

Terns have used the breakwaters for nesting because they are generally isolated from predators and human disturbance. However, the nearly century-old breakwaters provide low-quality or marginal nesting and chick rearing habitat. The surfaces are largely covered with broken concrete chips as a result of weathering, and lower portions of the breakwaters are subject to frequent wave overtopping.

In addition, there is little or no protective cover for the terns on the tops of these structures, and tern nests and chicks are exposed to wind, waves and weather. The sides of these concrete breakwaters are vertical, and chicks that wander too close to the edge may fall over and perish. Chicks too young to fly sometimes jump off the breakwater when disturbed or frightened and cannot get back on the structure because of its height above the water. This jumping of tern chicks can also occur when anglers' boats get too close to the structures, which are good habitat for several species of game fish.

The end cell on this old breakwater has been improved through the addition of pea-sized gravel and driftwood logs.
The end cell on this old breakwater has been improved through the addition of pea-sized gravel and driftwood logs.

Prototype design

Although the existing breakwater surfaces provided marginal nesting habitat, a number of elevated sections offered an opportunity to substantially improve the quality and area of nesting habitat for common terns on the Niagara Frontier. Despite the breakwaters' robust construction of concrete and rock, with several sections elevated about 10 to 15 feet above the water, they can be frequently overtopped by waves and ice, and even summer storms can have severe impacts on tern nesting. As such, the tern nesting habitat improvements needed to be strong enough to withstand the harsh weather conditions without jeopardizing the breakwaters' structural integrity or historic nature.

After careful consideration and consultation with a wide range of stakeholders, NYPA decided to construct a prototype improvement in 2009 on one of the Corps breakwaters known as Old Breakwater North. NYPA and its design team of engineers and biologists from Kleinschmidt Associates and Riveredge Associates, under the direction of project implementation consultants Gomez and Sullivan Engineers, developed this prototype Common Tern Habitat Improvement Project design, intended to meet the challenging installation requirements.

"NYPA worked collaboratively with U.S. Army Corps of Engineers regulatory staff and engineers on the project to improve common tern nesting habitat on the Corps' breakwaters in Buffalo Harbor, developing designs that minimized impacts to the breakwaters yet allowed relatively easy access for future inspections and maintenance needs," says Robert W. Remmers, P.E., chief, operations and technical support section for the Corps' Buffalo District. "NYPA completed the breakwater habitat project in April 2009, the same month that the Corps authorized it. NYPA kept the Corps sufficiently informed at all times, including during the construction process, post-construction site visits, and on the success of the nesting improvements."

The prototype common tern nesting installation created 2,100 square feet of high-quality nesting habitat on one of the highest parts of the breakwater - a sheet pile-encased, cylindrical concrete end-piece known as an end cell. Along the perimeter of the end cell, a pre-fabricated, bent-steel containment frame was anchored to the concrete surface. The frame was filled with pea-sized gravel as a nesting substrate and topped with a seasonally-installed plastic mesh fence to prevent common tern chicks from falling or jumping off the end cell. Driftwood and plywood shelters were added to the nesting area to provide structures and shade for the terns.

The prototype design also involved the use of a large commercial barge that was modified to provide pea-sized gravel as nesting substrate surrounded by plastic fencing to prevent the chicks from escaping. The barge was prepared on land and moored to one of the breakwaters in the harbor for the nesting season. Although this prototype design was successful and provided good nesting opportunities, it was determined not to be cost-effective to mobilize and store the barge each season. The permanent installations on top of the existing breakwaters were deemed more successful at providing a cost-effective nesting solution. The barge prototype design could be utilized at other locations where permanent structures such as the breakwaters are not available.

Success of the prototype enhancement

After construction of the prototype nesting habitat, installed just before the 2009 nesting season, terns immediately began nesting on the gravel. In fact, the first nest scrape was made within 24 hours after installing the new containment frame and gravel. Terns quickly began nesting in large numbers, and a month after the gravel installation was complete, the end cell had about 325 nests. The end cell improvement contained 50% of all tern nests on this particular breakwater, more than had ever been recorded here since DEC began keeping records. Terns that nested on this end cell had productivity (chicks fledged per nest) more than five times higher than terns that nested on the unimproved concrete sections of the breakwater.

In 2009, many nests on the unimproved, bare concrete of the breakwater failed due to high winds, waves and flooding from rainstorms. In contrast, the gravel on the end cell provided stable, well-drained substrate, and the resulting productivity was high. The improved end cell survived the winter of 2009-2010 with no damage and minimal loss of gravel material.

The success and benefits of NYPA's enhancements were again clearly demonstrated in 2010, when a spring storm with winds in excess of 60 miles per hour destroyed all tern nests in Buffalo Harbor except those on the enhanced nesting area constructed in 2009. In 2010, no tern chicks were fledged from terns nesting on unimproved, bare concrete areas, compared with an average of one to two tern chicks fledged per nest in the enhanced nesting area.

By June 10, 2010, 813 tern chicks were recorded in the improved end cell. In 2010, largely as a result of NYPA's Habitat Improvement Project, there were about 1,950 nesting pairs of terns in the Niagara Frontier. In contrast, few if any tern chicks survived on the unimproved nesting areas of the breakwaters, demonstrating the durability and merits of the Common Tern Habitat Improvement Project design.

With more than 2,200 tern chicks fledged in 2011, the habitat improvement project has proved an unqualified success.
With more than 2,200 tern chicks fledged in 2011, the habitat improvement project has proved an unqualified success.

Future plans

Based on the success of the prototype installed in 2009, NYPA expanded its Common Tern Habitat Improvement Project to include three additional sites on Buffalo Harbor breakwaters that were installed in October 2010 for initial use in 2011. In addition to a second end cell, two rectangular sections of the breakwaters were selected because of their flat surfaces, lack of slope and higher elevations, and these were improved using the same design principles as employed for the 2009 prototype. This brings the total new permanently improved nesting habitat under this project to 10,500 square feet, which was installed at a cost of $343,000.

Based on the two-year success of the prototype enhancement, including the fact that it alone accounted for all of the tern chicks produced in 2010 on the breakwaters, it was expected that the number of tern nests in Buffalo Harbor, including those birds drawn from other nesting areas, would reach a record high in 2011.

These expectations for success were fulfilled in 2011, with a record of 1,888 common tern nests recorded in late May during the annual index count of nests. Overall, 2,203 tern chicks likely fledged from the Buffalo Harbor breakwaters in 2011. Preliminary data from other tern researchers in the Great Lakes area indicates that no other Great Lakes common tern colony successfully produced more chicks in 2011.

Continued cooperative management between NYPA and its stakeholders, agreed to during re-licensing - including annual monitoring, seasonal maintenance and possible new construction of additional nesting areas on other undeveloped man-made structures in the Niagara River - will help restore this threatened species to New York's Great Lakes region.

"This project has been a tremendous success," says Adams, "and I believe NYPA's habitat improvement project of graveling and fencing the breakwaters will continue to have a significant positive impact to the Common Tern population of Western New York."


Stephen Schoenwiesner is licensing manager and Edward Alkiewicz is director with the New York Power Authority. Dr. Lee Harper is senior scientist and vice president with Riveredge Associates. Morris Perot is senior scientist with Kleinschmidt Associates. Schoenwiesner managed completion of the project's design and installation, while Alkiewicz provided implementation oversight and worked with stakeholders to identify key criteria. Harper and Perot worked to bring the project from concept to detailed design and implementation, and Harper performed initial baseline and post-implementation monitoring.

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