Common Tern Habitat Improvement Project:
2009 Buffalo Harbor Tern Colony
Enhancements and Status Assessment
Niagara Power Project (FERC No. 2216)
New York Power Authortity
©Copyright 2010. New York Power Authority. All Rights Reserved
Table of Contents
The New York Power Authority and Riveredge Associates would like to thank the Army Corps of Engineers for their cooperation in the implementation of the Common Tern Habitat Improvement Project on the breakwaters of Buffalo Harbor.
In addition, the New York Power Authority and Riveredge Associates would like to thank the New York State Department of Environmental Conservation for sharing many years of tern nesting data for Buffalo Harbor.
The New York Power Authority's (NYPA) Niagara Power Project (Project) is licensed by the Federal Energy Regulatory Commission (FERC). As part of the relicensing process, NYPA, state and federal resource agencies, local governments, nongovernmental organizations, and other stakeholders signed a Comprehensive Relicensing Settlement Agreement that requires NYPA to develop several habitat improvement projects (HIPs) in the vicinity of Project lands and waters. One of the HIPs involves enhancing the nesting habitat of the Common Tern (Sterna hirundo) within Buffalo Harbor.
The Common Tern is a state-listed threatened species whose numbers have declined primarily due to loss of suitable nesting habitat. In Buffalo Harbor Common Terns nest on three breakwaters. The number of nesting pairs of terns on these three breakwaters comprises the largest tern colony in the Great Lakes. Although terns nest in great numbers on these breakwaters, productivity of these nests is low due to of a lack suitable nesting substrate. The goal of the Common Tern HIP is to provide suitable and stable pea gravel nesting substrate on the Buffalo Harbor breakwaters to help increase tern breeding productivity and aid the recovery of this threatened species.
In 2009, two prototype habitat improvements were made to tern nesting habitat in Buffalo Harbor. The first improvement involved the installation of a containment structure, perimeter fence and gravel substrate on an existing cement-surfaced breakwater which terns use as a nesting site. The second experimental improvement was the creation of new nesting habitat on a barge moored to a Buffalo Harbor breakwater. The use by terns of these two experimental habitat improvements was monitored during the breeding season. The data collected were analyzed, assessed, and used to guide the future direction of this HIP.
This report summarizes the number of Common Tern nests and their productivity on the improved nesting habitat during 2009 and evaluates the success and costs of the project. These results provide guidance for additional habitat improvements for the Common Tern HIP in future years.
In the Great Lakes region, the Common Tern is considered an endangered species in Ohio, Illinois, Wisconsin and Vermont; a threatened species in New York, Michigan and Minnesota, and an extirpated species in Pennsylvania and Indiana (Cuthbert et al., 2003).
NYSDEC has monitored and managed inland Common Tern colonies on the St. Lawrence River, Oneida Lake, and the Niagara Frontier since the late-1980s. The decline in New York’s inland tern population and the low number of terns currently nesting on New York’s Great Lakes can be attributed to the loss of nesting habitat and low breeding productivity due to predation, poor nesting substrate, and human disturbance. The loss of nesting habitat is primarily the result of the tremendous increase in ring-billed gulls.
Since 1990, Riveredge Associates has managed St. Lawrence River Common Tern colonies in an attempt to increase the number of nesting pairs of this threatened species in the region. In 2004, Riveredge Associates was contracted by the New York State Department of Environmental Conservation (NYSDEC) to monitor and manage Common Tern colonies in Buffalo Harbor and the Niagara River as well (Harper and Adams, 2005; Harper et al., 2006; 2007; 2008; 2010). Riveredge and NYSDEC management efforts have attempted to increase the amount of available nesting habitat for terns, decrease the amount of competition for nest sites with gulls, decrease the amount of predation on adults, chicks and eggs, and increase public awareness to reduce human disturbance at tern nesting sites.
On the Niagara Frontier, Common Terns nest on breakwaters in Buffalo Harbor and potable water intakes and power tower cribs on the upper Niagara River. Annual monitoring of Common Tern nesting on the Niagara Frontier was started in 1986 (Adams and Batcheller, 1987) and conducted almost annually since. Riveredge was contracted by NYSDEC to conduct the monitoring of Common Tern nesting colonies on the Niagara Frontier for five years from 2004 through 2008. In 2009, Riveredge was contracted by NYPA to monitor the Common Tern habitat enhancements in Buffalo Harbor as part of NYPA’s Common Tern HIP. NYSDEC monitored and managed the other Niagara tern colonies with their own staff.
On the Niagara Frontier, Common Terns have nested at 13 sites on eastern Lake Erie and the upper Niagara River since 1986 (Harper et al., 2008). In and near Buffalo Harbor, these sites have included breakwaters and lighthouses such as the North Breakwater (also called Donnelly’s Pier or Donnelly’s Breakwall), Reef Lighthouse, Old Breakwater North (also called Short Breakwater), and Old Breakwater South (also called South Breakwater). On the Niagara River these sites have included potable water intake structures, power tower cribs, and islands associated with water control structures for generating hydroelectric power.
During the last ten years (2000-2009) terns have nested at nine of these sites in Buffalo Harbor and on the Niagara River. Terns were displaced from four nesting sites by gulls and cormorants. All current tern nesting sites on the Niagara Frontier are artificial structures such as breakwaters, power tower cribs, and water intakes.
The majority of Common Terns nest on three Buffalo Harbor breakwaters (North Breakwater, Old Breakwater North, Old Breakwater South). These breakwaters are multi-level structures of concrete and armor stone. The nesting substrate is composed largely of broken concrete chips where the breakwaters are weathering. There is little or no cover on 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 fall off the breakwater when disturbed or frightened cannot re-access the structure and perish.
Since 2004, tern management activities have included the construction of gravel nesting boxes, the installation of perimeter fences, the deployment of chick shelters, and the posting of informational signs on the Buffalo Harbor breakwaters (Harper and Adams, 2005, Harper et al., 2006; 2007; 2008; 2010). These materials were all installed in the spring and removed later in the year after tern nesting was over. Nesting boxes were built with 2x6 lumber and filled with gravel to provide better nesting substrate for terns and to increase egg hatching and chick fledging rates. Nesting boxes were built and installed on each of the three Buffalo Harbor breakwaters in one or more years for five years from 2004 to 2008 (Harper and Adams, 2005; Harper et al., 2006; 2007; 2008). Plastic perimeter fencing was installed to increase chick survivorship by preventing chicks from jumping off the structures. Plywood chick shelters were deployed to protect tern chicks from weather, territorial adults, and predators, and encourage chicks to remain near their nest for a longer period of time. Finally, informational signs were posted to inform the public of the nesting terns and to limit human disturbance. These NYSDEC Restricted Area signs list the New York State and Federal Statutes prohibiting the disturbance of Common Terns and indicate that the tern is a designated threatened species under New York State Environmental Conservation law. Human disturbance can cause a great deal of chick mortality on the Buffalo Harbor breakwaters. If anglers or recreational boaters approach the breakwaters too closely, chicks may panic and run, becoming separated from their parents or falling off the structures and perishing.
In 2009, the Common Tern HIP consisted of two prototype tern nesting habitat improvements in Buffalo Harbor. One of these improvements was to an existing nesting site on the end cell (a cylindrical sheet pile structure filled with concrete, used to buttress and stabilize the breakwater) of the Old Breakwater North. The second improvement was the creation of new habitat on a floating nesting barge moored to the North Breakwater. The end cell provided approximately 2,000 square feet of enhanced nesting area and the barge provided approximately 1,200 square feet of enhanced nesting area for Common Terns. Construction started in early April and was completed by April 17 as requested by NYSDEC. The locations of these two enhancements are depicted in Figure 3-1.
The top surface of the end cell of the Old Breakwater North was enclosed with a one-foot high galvanized steel angle iron containment structure. This containment structure was made of 16 pieces of galvanized steel bolted to the concrete. Once completely installed, the containment structure was filled with pea gravel nesting substrate to a depth of six inches using a barge and crane (Figure 3-2). The pea gravel consisted of non-crushed, naturally round stone with 70% to 90% of the material ½ in. to ¼ in. diameter, 10% to 30% finer than ¼ in. diameter, and less than 10% passing through a No. 100 sieve. Approximately 37 cubic yards of pea gravel was placed on the end cell.
A plastic perimeter fence was attached to the top of the steel containment frame. The plastic fence was tensioned with a polypropylene rope running around the perimeter and through eyes at the top of epoxy-coated rebar rods affixed to the containment frame. The fence was installed to keep tern chicks from jumping or falling off the structure.
Once the steel containment frame, gravel, and perimeter fence were in place, the interior of the structure was divided into four quadrants using 2x6 lumber and additional plastic fencing (Figure 3-3). The area was divided into four smaller sections to facilitate counting tern chicks and to prevent chicks from moving too far from their natal nest site. Driftwood was placed on the gravel to provide additional structure and separation among nesting terns. As tern eggs began to hatch, chick shelters were placed adjacent to nests to provide cover for chicks from adverse weather and predators.
The tern nesting barge was constructed of six portable barges pinned together to provide approximately 1,200 square feet of nesting area. Angle iron uprights were welded to the barge and an elevated floor of corrugated steel added on top. The sides were enclosed with plywood (Figure 3-4). Approximately 22 cubic yards of pea gravel was placed on top of this steel floor and spread to a depth of about six inches.
The barge was pushed out to Buffalo Harbor and moored to the south end of the North Breakwater. Heavy mooring lines (2”) and steel cables (3/4”) were used to moor the barge to existing eyes on the North Breakwater. The outside corners of the barge were anchored with one-ton concrete blocks. Plastic pipes affixed to the breakwater were used to prevent chafing of the mooring lines on the concrete breakwater (Figure 3-5).
Plastic perimeter fencing was attached around the outside of the barge to keep tern chicks from falling or jumping off the structure. Driftwood logs, restricted area signs, and chick shelters were added to the structure as well. The interior of the barge was divided into two sections to facilitate counting tern chicks and to prevent chicks from moving too far from their natal nest site.
The two nesting habitat improvements were monitored in 2009 to document the number and productivity of Common Tern nests. These sites were surveyed from late April through late-July. Monitoring followed the methods used for recent surveys (Harper et al., 2010) and were consistent with the “Protocol for Surveying, Monitoring and Managing at Common Tern Colonies in Upstate New York” developed by NYSDEC (NYSDEC, 2004). All monitoring activities were closely coordinated with NYSDEC and the results of field surveys forwarded each week to the NYSDEC Regional Biologist (Connie Adams), Wildlife Manager (Mark Kandel), Natural Resources Supervisor (Russ Biss), and representative to the NYPA Niagara Ecological Standing Committee (Joe Galati).
Tern colonies were surveyed approximately weekly as weather and colony conditions permitted. Two to five people participated in colony surveys. During periods where tern chicks were highly mobile, the frequency of colony surveys was reduced to limit the number of chicks that jump off the breakwaters. In addition, surveys were not conducted on windy days when older chicks were close to flying age. Chicks over 15 days old can be blown off the colony simply by opening their partially feathered wings. At this age, their flight feathers are long but the chicks are not yet capable of flight. If strong winds blow the chicks off the colony they fall in the water and die. Mid-to-late June surveys were often shortened or canceled due to the potential to lose a great number of chicks off the breakwaters.
Field notes collected during each monitoring event included the date of each observation, the site or location, general weather conditions, the number of nests counted, the number of live chicks and eggs present, the number of dead chicks and broken eggs present, and other pertinent information. Methods used were similar to methods previously used for monitoring Common Terns in Buffalo Harbor by NYSDEC (e.g., Harper et al., 2008).
On each survey, individual nests (or a subset of all nests) were numbered with permanent marker and the numbers of eggs or chicks in the nest recorded. Selected nests in each colony were monitored to determine the number of chicks that hatched and fledged. On each survey, live chicks were counted. Dead chicks were counted and removed from the colony.
Tern chicks were banded with Incoloy, a stainless steel alloy, leg bands. Chicks were banded at approximately five days of age and older. Efforts were made to band all chicks within the end cell and barge to provide an accurate total chick count and to provide data on productivity, survivorship, and post-fledging dispersal.
The number of tern nests and the number of tern chicks that survived to fledging were used to assess the success of the enhanced nesting areas. Average productivity was calculated by counting the total number of tern chicks fledged and dividing this value by the number of tern nests that produced these chicks to calculate the average number of chicks fledged per nest. Productivity for 2009 was compared to the productivity of these breakwaters for the previous five years (e.g., Harper et al. 2010).
In addition to productivity, nest density, maintenance and monitoring needs (e.g. number of shelters, needed repairs), and a cost-benefit analysis of the number of chicks produced in relation to the cost of the enhancement were also calculated. Combined, these data were used to assess the success of the tern nesting barge and the end cell habitat improvements, and to guide future decision making about potential methods and schedule for this HIP.