THE WETLANDS INSTITUTE

VEGETATION
MANAGEMENT PLAN
STONE HARBOR BIRD SANCTUARY

APRIL 2014
1075 STONE HARBOR BOULEVARD, STONE HARBOR, NJ 08247

Invasive Species

According to the State of NJ Executive Order 13112, an invasive species is defined as a species that is:

• non-native (or alien) to the ecosystem under consideration, and
• whose introduction causes or is likely to cause economic, environmental harm, or harm to human health.

Invasive species can be plants, animals, fungus, pathogens or algae. Human actions are the primary means of invasive species introductions, and may be through intentional introductions (e.g. landscape and pet trade) and accidental introduction (e.g. packing crates and bilge water) ( opens in a new windowwww.njisst.org/invasive-species.asp). Once present, birds and other wildlife also spread invasive plants.

For the Stone Harbor Bird Sanctuary, the focus of this management plan will be on invasive plants and the impacts that they may have on overall Sanctuary biodiversity, habitat health and stability, and habitat suitability for migratory songbirds and nesting colonial wading birds. The SHBS also serves as an important natural area in an otherwise heavily developed barrier island community. As such, it is an important refugia for certain animals and plants that will benefit from management of invasive species.
Invasive Species Control
Invasive species management and control can typically take 3 approaches:

• Prevention: This control method usually employs outreach and education. Rarely, legislation is employed to limit the import or distribution of invasive plants, and state level designations can limit the use of plants significantly. Outreach may include making people aware of the effects of invasive plants, education on recognizing common invasive plants and management strategies so they can manage invasive plants locally, and warning people about
  common transport mechanisms of invasive plants and their establishment, and encouraging people to stop purchasing invasive landscape plants.
• Early Detection/Rapid Response: The focus of this control measure is on identifying invasions as they are emerging in order to prevent them from impacting native species and while their impact is still limited. The goal is to fully eradicate identified target species.
• Control and Management: This control method is employed where invasive species have become established. The focus is on the protection of sites with high conservation value and utilizes long-term control programs to reverse larger infestations of widespread species. The goal is restoration of the site.

An effective vegetation management strategy for the Stone Harbor Bird Sanctuary should employ all three strategies. Large portions of the sanctuary already suffer significant infestations that have impacted habitat and overall site biodiversity. In other areas, new invasions have been identified and early detection and rapid response will be an ongoing and important management tool to limit intensification. The mission statement for the SHBS includes education as a recognized goal. The addition of education related to invasive species, their management, and prevention will be necessary to create and environment for sustainable management of the Sanctuary for the future.

Description of Sanctuary Habitats
Pre-rejuvenation Major Vegetation Subgroups
The SHBS Master Plan identifies four areas of major vegetation subgroups (Map 3)(Duffield, 2006). These vegetation subgroups and the vegetation that characterized them prior to implementation of the restoration plan (2006) is presented:

Area 1: Tidal Salt Marsh

• Saltmarsh Cordgrass (Spartina alterniflora) – dominant,
• Saltmeadow Cordgrass (Spartina patens) – dominant,
• Common Reed (Phragmites communis) – fringe, and
• Marsh Elder (Iva frutescens) – ditch banks.

Area 2: Disturbed Salt Marsh

• Common Reed (Phragmites communis) – dominant,
• Marsh Elder (Iva frutescens) – ditch banks, and
• Sea Lavender (Limonium carolininium) – scattered.
• Area 3: Late Successional Dune Woodland/High Dune Maritime Forest
• American Holly (Ilex opaca)
• Black Cherry (Prunus serotina)
• Sassafras (Sassafrax varifolium)Red Cedar (Juniperus virginiana)
• Black Pine (Pinus thunbergii)
• Japanese Honeysuckle (Lonicera japonica)
• Green Briar, Cat Briar, Horse Briar (Smilax spp.)
• Poison Ivy (Rhus radicans)
• Virginia Creeper (Parthenocissus quinquefolia)
• Area 3 included two smaller areas. Area 3a included an area dominated by Black Cherry and American Holly with a paucity of invasive vines. Area 3b identifies the freshwater pond that would later become Paul’s Pond.

Area 4: Holly/Knotweed Meadow

• American Holly (Ilex opaca)
• Japanese Knotweed (Polygonum cuspidatum, Fallopia japonica) – dominant

These areas predate the restoration plan and some areas have been modified through tidal and/or freshwater flow augmentation, vegetation management, and plantings. Other areas, especially areas 1 and 3 remain largely as described. The descriptions are provided as a baseline characterization to the SHBS.

Sanctuary Management Areas (2006 Plan)
The SHBS Master Plan also identifies both restoration areas and management areas. Area 2 is designated for marsh restoration and is the area that is most modified by tidal flow augmentation and water management. A berm structure also enhances the freshwater marsh in a portion of area 2. The Meadow Walk Trail now follows the top of the berm structure. Significant portions of area 3 are designated as songbird management areas. The wetland fringe bordering area 3 was designated a wading bird management area (Map 3) though specific distinctions between the songbird management and wading bird management areas are difficult to discern from the 2006 report.

These designations are useful for consideration as it relates to the development of vegetation management plans. Both types of bird management areas require vegetation management to maintain habitat suitability. Habitat suitability requirements are species or guild specific, but a few primary components are critical to determining suitability. Primary habitat characteristics include such factors as food availability, presence of suitable canopy and understory characteristics to promote safe roosting and nesting, predator security, and disturbance frequency. The dominant strategy for invasive and aggressive vine management in the Sanctuary involves cutting vines and in some cases, removal and clearing of underbrush. The target habitat should be comprised of mature trees with native shrub and ground cover extending to a height of 3-8 feet above the ground. In areas designated for songbird habitat, the ground cover and understory can extend higher and a moderate presence of native vines is desirable as a food resource.

These designations are useful for consideration as it relates to the development of vegetation management plans. Both types of bird management areas require vegetation management to maintain habitat suitability. Habitat suitability requirements are species or guild specific, but a few primary components are critical to determining suitability. Primary habitat characteristics include such factors as food availability, presence of suitable canopy and understory characteristics to promote safe roosting and nesting, predator security, and disturbance frequency. The dominant strategy for invasive and aggressive vine management in the Sanctuary involves cutting vines and in some cases, removal and clearing of underbrush. The target habitat should be comprised of mature trees with native shrub and ground cover extending to a height of 3-8 feet above the ground. In areas designated for songbird habitat, the ground cover and understory can extend higher and a moderate presence of native vines is desirable as a food resource.

Sanctuary Management Areas (2014)

With the successful completion of the Sanctuary restoration plan, the Sanctuary now has four primary biocommunities (Map 1)

• Tidal/Nontidal Marsh
• Freshwater Marsh and Pond
• Successional Meadow
• Upland Forest

These four biocommunities provide a basis for the designation of management areas within the Sanctuary and then include consideration of habitat suitability for bird usage. See Map 4.

• Tidal /Nontidal Marsh Management Area
• Freshwater Marsh Management Area
• Successional Meadow Management Area
• Song Bird Management Area
• Wading Bird Management Area

The Tidal/Nontidal Marsh Management area should be monitored and managed to maintain appropriate tidal exchange with the adjacent estuary. This should be managed by the Borough of Stone Harbor and will involve coordination with the Cape May County Mosquito Commission for maintenance of ditches and channels, and management of the flow structures by the Borough Department of Public Works. Vegetation management will include management for the Common Reed (Phragmites). It should be noted that it is unlikely that Phragmites will ever be completely eradicated from the Sanctuary. Goals for Phragmites management should focus on containment in its present areas and in some cases reduction. The most effective control mechanisms in the Tidal/Nontidal marsh areas are flooding or root saturation with salt water. This can be managed through targeted flow management of the water control structures. The distribution of Phragmites should be monitored to determine if the distribution is changing and if chemical control becomes warranted.

The Freshwater Marsh Management area should be monitored for the presence and maintenance of suitable hydrology to maintain the freshwater marsh ecosystem. If the hydrology of the freshwater system deteriorates, an evaluation of suitable remedies can be evaluated at a future date. Vegetation management in the freshwater marsh area involves primarily management of Phragmites however, other invasive plants favor moist conditions and their appearance in the freshwater marsh or marsh fringe should be immediately managed. Japanese knotweed has been present in the freshwater marsh and has been successfully eradicated through chemical control methods administered by the US Fish and Wildlife Service. The freshwater marsh area has also been subjected to chemical control and management of Phragmites. This control has helped to keep the Phragmites cover limited and the density of cover thin. This management strategy should be continued along with routine inspection for new invasions and recurring outbreaks of Japanese knotweed.

The Successional Meadow Management Area is comprised of a mixed assemblage of warm- season grasses, shrub-scrub habitat, and some areas of wet meadow. Historically this was an area of significant Japanese knotweed invasion that has been managed through mechanical and chemical means by the US Fish and Wildlife Service. Native vegetation was reintroduced into the area and is doing well. Management of the successional meadow will involve maintaining vigilance for outbreaks of Japanese knotweed and immediate eradication of new invasions. The southern end of the meadow has Phragmites and this area could be managed through chemical means to limit its
expansion. At some point, this area will continue to succeed back to a forested habitat. It is worth considering if the area should be maintained to hold it in an early successional phase to maintain this habitat type in the Sanctuary. This management would involve selective removal of saplings to maintain the meadow characteristic.

Songbird Management Areas are located in the upland forest areas that are largely located along the western boundary of the Sanctuary. The songbird management areas will overlap significantly with the wading bird management areas with the primary differentiation being proximity to the marsh boundary for the wading bird areas. Both areas are forested areas and suffer invasion to varying degrees by the target non-native invasive and aggressive native vines. Management and control will be similar for both areas with the primary difference being in the degree to which the understory is managed. Dead and dying trees will be maintained as a valuable habitat asset to wildlife where possible and appropriate.

Wading Bird Management Areas are focused along the eastern portion of the Sanctuary and extend to the boundaries with the tidal/nontidal and freshwater marsh areas. These areas are invaded to varying degrees by the target non-native invasive and aggressive native vines. Management and control will be similar to the songbird management areas with the primary difference being in the
degree to which the understory is managed. Understory should be managed to slightly lower and more open conditions in the wading bird management areas, as possible, to maintain the integrity of mature trees and saplings. As with the Song Bird Management Areas, dead and dying trees will be maintained as a valuable habitat asset to wildlife where possible and appropriate.

Invasive Species Occurring at Stone Harbor Bird Sanctuary
The Stone Harbor Bird Sanctuary currently suffers from extensive encroachment of both nonnative invasive vines, as well as native aggressive vines. Currently, this is one of the most significant factors that limits the ecological wellbeing, and diversity of Stone Harbor Bird Sanctuary and that of the birds that have historically nested there. Predation and disturbance are also significant factors that are not the subject of this plan but should be noted.

Table I documents the dominant known invasive nonnative and aggressive species occurring in the Sanctuary. This table comprises the species targeted for management because of the significance of the impact and threat that they pose to biodiversity and habitat suitability at the Sanctuary.

Table I: Known Invasive and Aggressive Plant Species Occurring at Stone Harbor Bird Sanctuary

* both native and non-native strains occur but the non-native strain is believed to be the invasive version.

The table of identified and target species for vegetation management at the Sanctuary represents a listing of known invasive species. It is likely that additional invasive plants are present in the Sanctuary and will be identified and assessed as ongoing vegetation management occurs and new areas are investigated and addressed.

The list of non-native invasive species present in the Sanctuary pose differing degree of risk to Sanctuary habitats based on plant physiology and behavior that determines both the speed at which they dominate ecosystems, as well as the degree of difficulty required to manage and control them. The most significant invasions to the Sanctuary from an impact and risk perspective involve Porcelain berry, English ivy, Sweet Autumn Clematis, Common reed or Phragmites, and Japanese
Knotweed, Green, Cat, and Horse Briar, aggressive native species, are also causing significant impacts to both the tree canopy and understory in the Sanctuary. Wild grapes are also a significant management challenge. They are impacting canopy cover but are a beneficial source of food and cover for nesting and foraging songbirds. Thus, management of wild grapes needs to be balanced against its habitat value. Virginia creeper also falls into this same category.

Prioritization for Management

To better prioritize areas in greatest need of vegetation management, the Sanctuary has been divided into smaller areas within management zones. These areas have been defined by the level of invasive plants present in an area (high, moderate, low, trace). In many cases, the abundance of invasive or aggressive vines has significantly covered the forest canopy resulting in heavy stress to mature forest areas (Photo 1). Other areas have moderate levels of infestation with significant invasion largely confined to the understory (Photo 2). While both of these impacts require management, that management needs to be ongoing and diligent. Some areas of the Sanctuary would benefit from immediate and urgent rescue of trees. In others areas, new invasions are just beginning and should be managed immediately in the localized area (Photo 3). Thus, this management plan first designates the

level of invasive and/native aggressive plant presence and then applies a decision matrix to recommend action areas. In some areas, it is recommended that initial vine cutting be implemented to provide relief for stressed mature trees without additional management for the time being. For the vegetation management plan at the Sanctuary to be successful, designated vegetation management project areas need to be managed for successive growing season. It is not prudent to overextend and initiate vegetation management in too many areas to allow for proper follow up and vigilance. Thus a phased approach is required and recommended. This approach will require considerable follow up management in most areas following initial invasive species removal to ensure that the area does not revert back to previous impact levels.

Photo 2. Area of Stone Harbor Bird Sanctuary with moderate level of infestation with significant invasion largely confined to the understory. The tree canopy is still largely unaffected and healthy.

Photo 3. A new invasion of Japanese knotweed in an area of the Stone Harbor Bird Sanctuary. This plant is highly invasive and difficult to manage. The newly identified area should be managed quickly before it can become established.

Map 5 documents the relative abundance of invasive non-native or aggressive native species in a given area. In some large areas of the Sanctuary, especially the Songbird Management Area on the eastern and southern portions of the Sanctuary, the area has been designated as having moderate levels of invasive plants, it is likely that the degree of invasive plant presence is variable in the area.

The prioritization of work areas to manage invasive plants in the Sanctuary will be based on a decision matrix that accounts for a) the degree of invasion, b) current or historic use by priority species, c) the ease of access to an area, d) the ability to manage and maintain the area in a natural state, e) available resources, and f) the present condition of the area which will continue to evolve based on response to management.

Map 5. Map depicting the relative levels of invasive plant occurrence in the Stone Harbor Bird Sanctuary.

Action Plan By Management Area

Wading Bird Management Area/ Songbird Management Area

With one of the primary purposes of the SHBS focused on preservation and restoration to encourage the reestablishment of colonial wading birds, an initial work area addressed this goal. To further prioritize the management area, the area of historic wading bird nesting, and reported area of wading bird roosting was selected. This area (Map 6) is located in the vicinity of Holly Path near Paul’s Pond, and is easily accessible to maintenance workers. The area suffered from a heavy presence of
nonnative invasive and aggressive native vines that had covered trees, dominated the understory, and provided ready access to potential nesting and roosting area by predators.

The recommended strategy for managing nonnative invasive and aggressive native vines involves manual cutting of vines followed by removal, where possible, from trees. In most instances, it is better to simply cut the vines and allow them to die and naturally fall from the trees. Cuts should be made near the ground, and then again several feet up from the ground removing the section of vine. In areas of significant infestation, clearing of the understory by mechanical methods, followed by brush mowing can be effective. Mechanical removal of vines and understory will open the canopy and understory and provide much needed respite to trees and allow them to leaf out and begin to recover. Mechanical clearing alone will not eradicate non-native invasive and aggressive native vines. They will resprout and regrow in the following growing season. Following mechanical removal with chemical treatment will be required in most areas. Areas will need to be inspected throughout the growing season and in successive years with spot treatments to manage regrowth of unwanted plants.

The continual management required to fully manage some infestations will be further complicated by disturbance management measures implemented to encourage colonial wading bird nesting. Specifically, access to the Holly Path will be seasonally restricted thus management will need to occur during the fall, winter and early spring (October 1 – March 1).
Photo 4 shows the wading bird management areas in the vicinity of Paul’s Pond immediately following clearing of vines and invasive understory in February 2014. Photo 5 shows the area around Heron Overlook before and after work to clear invasive plants from the area in March, 2014.

Successional Meadow Management Area

The recommended strategy for management of the successional meadow involves vigilance for outbreaks of Japanese knotweed followed by either mechanical removal or chemical treatment of identified plants. Japanese knotweed is extremely difficult to manage so that it is critical that any new infestations be managed immediately while they are still isolated plants occurrences.

Phragmites management in the successional meadow will involve chemical treatment on an annual schedule. Treatment is most effective in early fall as the plants are beginning to senesce. During this time, plants draw chemicals down into the roots resulting in more effective control.

Freshwater Wetland and Pond Management Area

The primary management need in the freshwater wetland is the management of Phragmites. Portions of the freshwater wetland are only moderately impacted, while the area around Paul’s Pond has a heavy Phragmites presence. Managing Phragmites will be a very difficult task as chemical means are the only really effective strategy. However, this needs to be carefully balanced with the acceptable risk to

other freshwater plants and animals. The US Fish and Wildlife Service recommends foliar spraying for Phragmites in the early fall. This is a time when the wetland is seasonally dry limiting impact form chemical application. Chemical application should be limited to areas with moderate presence of the plant and should be used to maintain thinner density to allow for native plants to gain a foothold.

In areas of heavy, dense Phragmites, a combination of mechanical cutting followed by chemical control of newly sprouting plants, or fall application is an appropriate strategy. In the area around Paul’s Pond, the presence of roosting and potential nesting colonial water birds makes spring
chemical treatments impossible. This complicates the management of the Paul’s Pond area and limits management to the fall season after birds have departed the site.

Portions of the freshwater wetland fringe suffer from Multiflora rose dominance. This area is most notably in the area at the northwest corner of the marsh. Multiflora rose management is best accomplished by cutting followed by stems and following with stem application of herbicide. It is most effective when conducted prior to the plants going to seed as birds spread roses very effectively.

Tidal and Nontidal Salt Marsh

The primary management need in the tidal and nontidal salt marsh is the management of Phragmites. In most areas in the salt marsh, management of Phragmites is best accomplished through manipulation of water levels to cause inundation or root saturation with salt water. Hydraulic manipulation of tidal flow should be attempted before additional management strategies for Phragmites are attempted. It is extremely likely that Phragmites will never be eradicated form the Sanctuary. Rather, management should be focused on limiting its expansion and limiting it to thin cover to allow native vegetation to gain a foothold.

Management Approach and Strategy

This Vegetation Management Plan will be implemented by the Borough of Stone Harbor. The Wetlands Institute will continue to work in coordination with the Borough, SHBS Committee, and state and federal partners as needed. Volunteers will be recruited from the community as an educational component to learn about invasive species occurrence and control.

Recommendations for Continued Plan Development

Adaptive Management Plan

As vegetation management continues in the Sanctuary, there will be opportunities to collectively manage other aspects of the Sanctuary. These various management strategies should be coordinated and be complimentary to each other. Adaptive management will be an important tool for continued

evaluation of the vegetation management plan, as well as disturbance management at the Sanctuary. Compatible usage is an important consideration that will also need to be addressed and incorporated into management strategies for the Sanctuary.

Biological Monitoring Plan

The best way to measure management effectiveness for the Sanctuary is to measure site utilization by target species. A biological monitoring plan should be developed that identifies the suite of possible studies that would benefit the Sanctuary, as well as potential funding sources to implement species monitoring. Avian and herpetological monitoring come immediately to mind.

Predator and Disturbance Management Plan

Predator and human disturbance management can ultimately be the most important factors that determine if nesting colonies of wading birds can be reestablished in the Sanctuary. The vegetation management program is the first important step, but without concomitant management of predators and disturbance, the ultimate success of the Sanctuary restoration objectives is less likely. Steps have
been taken to minimize disturbance in key areas of historic and current colonial bird roosting and nesting. Educating the public about these measures, and continually managing disturbance will be critical. The Sanctuary should have a well-articulated plan for managing both human disturbance and predators.

References Cited
Duffield Associates, 2006. Stone Harbor Bird Sanctuary Rejuvenation Project, Preliminary Master Plan, Prepared for borough of Stone Harbor, May 2006.

http://www.njisst.org/invasive-species.asp