Rattray Marsh Frequently Asked Questions

Explore Rattray Marsh FAQs by Category


Rattray Marsh provides important habitat for many species of birds, butterflies, amphibians, reptiles and mammals because of the scarcity of large natural areas along the Lake Ontario shoreline west of Toronto. The marsh is particularly important for migratory birds in the spring and fall. During this time, many birds travel across Lake Ontario and along the shoreline and stop at Rattray Marsh to rest and feed. This includes species of songbirds, ducks, geese, birds of prey, herons and shorebirds.

In general, Rattray Marsh will see more species of birds during the spring and fall migration periods than at any other time of year. For instance, birds destined to breed up north, like bay-breasted warblers, will find refuge at Rattray Marsh.

Rattray Marsh is home to many breeding bird species. The variety of plant communities, including deciduous and mixed forest, and cattail marsh, provide ideal breeding conditions for different types of birds.

Birds that breed in or near the forests include pileated woodpecker, white-breasted nuthatch, eastern screech-owl, great horned owl, ovenbird, hairy woodpecker, northern flicker, eastern kingbird, cedar waxwing and red-breasted nuthatch. Birds that occupy the marsh include Virginia rail and mallard.

Other bird species, such as great blue heron and common tern, may use Rattray Marsh temporarily; for example, for feeding.

To determine how the bird community has been impacted by emerald ash borer, CVC conducted breeding bird surveys in 2014 prior to ash tree removals, and again in 2022 after ash tree removals. Analysis is currently underway, but preliminary results suggest that most of the same species are breeding at Rattray Marsh.

The invasive emerald ash borer (EAB) arrived in Mississauga in 2008 and since then has destroyed nearly all native ash trees in the area.

CVC began felling dead or dying ash trees in in 2014 to ensure visitor safety from failing trees and to accelerate reforestation by planting a healthy diversity of tree species. Felling dead or dying ash trees resulted in changes to the bird community. With fewer ash trees, the forest canopy has opened, exposing the ground to more sun. Forest birds can still find refuge among the remaining trees or by moving to other areas of the conservation area where ash removal was minimal.

Some birds prefer open areas of the forest. Species like northern flicker, indigo bunting and great crested flycatcher will live in areas like this. Other birds, like song sparrow and American goldfinch, will use areas closer to the ground.

As the new trees and shrubs planted by CVC mature, the forest canopy will close. At that time, the diversity of birds that are attracted to the area will also shift.

To determine how the bird community has been impacted by EAB, CVC conducted breeding bird surveys in 2014 prior to ash tree removals, and again in 2022 after ash tree removals. Analysis is currently underway, but preliminary results suggest that most of the same species are breeding at Rattray Marsh.

Since 2010, CVC has planted over 7,000 native trees and shrubs at Rattray Marsh. Over 900 of these trees and shrubs were planted in 2022 alone! The planted trees and shrubs include species that produce fruits and nuts, like dogwoods and oaks. As these species mature, they will provide a food source for birds. Cedar waxwing, for instance, will greatly benefit as they feed almost entirely on fruits. CVC is also controlling invasive species, such as buckthorn, which are less desirable to birds, to ensure the native trees and shrubs can grow.

By planting a variety of trees and shrubs CVC is providing habitat to birds that occupy different layers in the forest. The canopy, subcanopy, shrub and ground layers of the forest will attract different species of birds. Ultimately, the diversity of birds will increase as the plants mature.

Rattray Marsh is home to several turtle species. Snapping turtles and midland painted turtles are the most common turtles you will see in the marsh. Blanding’s turtle and map turtles are occasional visitors from Lake Ontario. You may also see red-eared sliders, a non-native turtle kept as pets and often released into the environment. They compete with native turtle species for food and resources.

Around June, female turtles leave the marsh and come on land to dig a nest and lay their eggs. They like to lay their eggs in loose soils with sunny exposure and at Rattray Marsh Conservation Area, this means they sometimes nest on the sides of trails, in the parking areas and in piles of mulch. Park activities, such as hiking, biking and trail maintenance, have the potential to put nests at risk.

Turtle eggs are food for many wildlife species and only a very small number (less than one per cent) will hatch and survive to adulthood. Predators of turtle eggs, such as raccoons, skunks and foxes are common within Rattray Marsh and you may see evidence of turtle eggs that have been dug up and eaten.

All Ontario turtle species are considered Species at Risk (of extinction), and Rattray Marsh provides important habitat for them. CVC seeks ways to protect and enhance turtle habitat to ensure our turtle populations continue to thrive within our parks.

  • We use wildlife data collected by CVC staff and naturalists, as well as wildlife data submitted to online databases (such as iNaturalist and eBird) to guide the management of our properties. This data helps us understand how the park is being used by wildlife and helps us identify areas of the park that need protection.
  • We consult with species at risk biologists at the Ministry of the Environment, Conservation and Parks (MECP) and obtain all necessary approvals when undertaking projects that may impact turtles.
  • We shift park management activities to avoid critical turtle nesting times.
  • We install nest protectors, which protect eggs from predators until they hatch.
  • We add artificial nesting sites to give turtles a safe place to lay their eggs and add basking logs in areas where there is a shortage.
  • We can install ecopassages to help turtles cross trails and roads safely.
  • We conduct specialized turtle inventories, using trapping and radio telemetry, to determine what turtle species use the park, what habitats they are using and where they are overwintering.

  • Submit your turtle observations to iNaturalist. One of the most important things you can do to help conserve turtles in the park is to report your observations. If you encounter a turtle, find a turtle nesting, or see eggs that have been dug up, please report it.
  • Do not disturb a nesting turtle. The stress can cause the turtle to leave without laying her eggs and she may risk returning another day to try again. Please watch from a distance and keep your pets away from the animal.
  • Do not dig up or move turtle nests. It is illegal to take wildlife into captivity or disturb the nests of endangered or threatened species. Interfering with the nests and eggs, even slightly, can kill the eggs or hatchlings.
  • If you see a hatchling turtle on the trail, please move it to the other side of the trail in the direction it was travelling. Do not move the hatchling to water – the movement from nest to water is an important time in the life of the turtle.
  • If you find an injured turtle, seek advice from an authorized wildlife rehabilitator.
  • For more information on turtle nests, we recommend the following websites:
    Why the turtle crossed the road & other FAQ’s about turtle nests
    Ontario Turtle Conservation Centre

Sediment Removal and Restoration

CVC conducted the Rattray Marsh Class Environmental Assessment (EA) in 2009: Rattray-Final-ESR-August09-Report.pdf (cvc.ca).

The purpose of the EA was to develop a restoration plan for Rattray Marsh that reflected the vision, goal and objectives of the Steering Committee. The EA Steering Committee included representatives from CVC, City of Mississauga, Region of Peel, Ministry of Natural Resources and Forestry, local naturalists, and the Rattray Marsh Protection Association.

The EA set three targets, including increasing open water area, improving water clarity and restoring the marsh substrate. The EA preferred alternative included the exclusion of carp and “the removal of mineral soil, the biological removal of nuisance species, and the reintroduction of indigenous plant species, benthic invertebrates and fish in Rattray Marsh”.

Excess sediment was removed from Rattray Marsh in 2014 (winter) and 2015 (winter), which exposed the native substrate and peat.

A total of 9,977 m3 of mineral soil was removed from the marsh, 12,000 m2 (about the area of a city block) of habitat was restored and 21 habitat structures were installed.

The dredging, as well as carp exclusion (described below) achieved the targets set out in the EA and CVC has documented significant improvements in the overall health of the marsh.

A Sheridan Creek sediment budget study was initiated in 2019 examining the relationship of Sheridan Creek to Rattray Marsh. Results from this study are anticipated to be ready in 2023. Sheridan Creek is the primary source of sediment entering the marsh.

Early results show a sedimentation rate of 1 – 1.5 cm/yr within the marsh. This suggests that it will take about 35 to 55 years to infill the marsh to previous sediment levels.  The Sheridan Creek sediment budget study will help understand the complex interaction between stream, marsh and Lake Ontario, and to help refine future restoration and management activities.

CVC is currently working landowners throughout Sheridan Creek to enhance properties, including actions to reduce sediment, such as IMAX CanadaGreen Glade Senior Public School, Xerox Canada, HL Blachford, Musket Transport and Walden Circle Condos.  For more information on these programs please refer to:

Greening Corporate Grounds – Credit Valley Conservation

Low Impact Development – Credit Valley Conservation

Common Carp

Common carp were imported as a potential food item from Europe to the United States and then to Canada in the 1880s. Over time, through a combination of pond failures or formal introductions in tributary streams, they made their way into Lake Ontario.

Carp uproot plants as they feed, stirring up sediment, destroying aquatic vegetation and habitat, and ruining the quality of the water. They also lay and fertilize eggs among native plants, negatively affecting them.

Due to their large size, adult carp can dig up and harm wetland plants faster than they can grow back. Plants are the foundation of the Rattray Marsh coastal wetland system and adult common carp cause significant harm to wetland health.

Several techniques to exclude carp from Rattray Marsh were assessed through an Environmental Assessment (i.e. fencing, construction of berms or weirs). Ultimately, fencing was chosen due to its effectiveness, ease of replacement, smaller footprint and reduced impact.

Fencing was strategically installed in portions of the marsh restoration areas to deter and exclude adult carp. Carp continue to have access to Sheridan Creek and the central portion of the marsh.

Early results indicate we were successful in deterring adult carp from entering the restored marsh  based on the persistence of aquatic vegetation.

CVC periodically inspects and maintains the fencing to fix underwater breaches or toppled portions of the fence. You may observe the occasional carp in the restored areas due to the breaches but the numbers of carp entering have been reduced significantly.

Protecting wildlife and enhancing wildlife habitat is critical to the work we do. CVC is taking appropriate measures to ensure carp control fencing does not negatively impact other wildlife at Rattray Marsh.


CVC currently uses fencing to keep common carp out of the marsh.

After sediment was removed from the marsh, black filter fabric was removed from the fencing. This change in design had an unanticipated and negative effect on wildlife with some birds striking the fence. As a short-term solution, CVC staff in consultation with the Canadian Wildlife Service added visual aids including neon pink flagging tape to reflect UV light.  The structure of swan eyes allows them to see UV light. Wooden posts were also added to the fence.

In spring of 2022, the black filter cloth was once again incorporated into the fencing to provide an enhanced visual deterrent to wildlife in Rattray Marsh. Filter fabric was used on the fence while sediment was being removed and there were no recorded incidents of wildlife striking the fence.


CVC will revisit options for permanent solutions to isolate open water portions of the marsh based on findings of Sheridan Creek sediment budget study (2023-2024).

Conservation Area Management Activities

CVC is committed to the protection of wildlife and wildlife habitat throughout the Credit River Watershed. Rattray Marsh serves as an important protected environment for a significant number of wildlife species as well as being an important recreational and educational resource for the community.

CVC uses several approaches to address threats and protect wildlife, including:

  • Park Planning and Management: CVC is guided by its Conservation Areas Master Strategy and its Conservation Lands Management Manual, which consolidates policy, procedure and best practices for management and operations of CVC lands.
  • Ecosystem Restoration: More than a century of land clearing, agriculture and urban development buried Rattray Marsh’s organic soils under a metre of sediment. CVC removed that sediment in 2014 and 2015 to restore Rattray Marsh to a healthier sustainable ecosystem.
  • Aquatic Invasive Species Management: Non-native carp uproot aquatic plants and disturb the sediment in Rattray Marsh. The resulting muddy water prevents plants from growing and negatively affects other wildlife. CVC has installed a barrier to protect the marsh from this invasive species.
  • Forest Management: Emerald ash borer (EAB) has devastated woodlands across Ontario and has resulted in a significant loss of forest cover in Rattray Marsh. Dead trees were cut down to protect public and staff safety. From 2010 through to 2022, CVC has planted over 7,000 native trees and shrubs at Rattray Marsh. Over 900 of these trees and shrubs were planted in 2022 alone! These plantings will help reduce the impact of this loss and speed up the recovery of Rattray Marsh. To learn more about our work managing EAB at Rattray Marsh, please visit our Ash Tree Management at Rattray Marsh.
  • Sustainable Trail Design: A sanctioned trail system helps to direct inappropriate uses away from environmentally sensitive areas to protect wildlife while at the same time providing high quality experiences for visitors to safely view and appreciate the natural environment of the property. Elevated boardwalks help protect sensitive soils and allow for the movement of wildlife underneath. Handrails are used to guide people and pets from wandering off trails and disturbing wildlife and their habitat.
  • Sustainable Infrastructure Development: Visitor infrastructure, like the boardwalk, are planned by in collaboration with CVC ecologists, who help determine the best way to avoid, minimize and mitigate disturbances to wildlife and vegetation. For example, low-impact boardwalk construction was done outside of the bird breeding window to avoid disturbing them during this critical period, and erosion control and exclusion fencing was used to protect wildlife during installation.
  • Outreach and Education: CVC works with community partners to protect and restore the natural areas of Rattray Marsh. This includes organizing and supporting community events to increase forest cover, create wildlife habitat and improve water quality in Sheridan Creek and the marsh. Interpretive signs inform visitors about the significance and sensitivity of the marsh.

  • Monitoring of Rattray Marsh by Canadian Wildlife Service (2010-2021) as part of Great Lakes Coastal Wetlands Monitoring program. Indicators include fish, birds, amphibians, wetland vegetation, aquatic macroinvertebrates and water quality. Detailed Coastal Wetland Monitoring Program (CWMP) Reports and publications are available online. For more information visit greatlakeswetlands.org.
  • CVC staff have been monitoring the marsh following the removal of sediment in 2015. Indicators include aquatic vegetation, sediment, photo monitoring, as well as assessing and repairing carp control fencing as needed.
  • Ongoing monitoring by CVC staff includes assessing the effectiveness of priority invasive species control projects and monitoring for new invasive species to Rattray Marsh. This includes forest pests such as hemlock woolly adelgid and oak wilt.”
  • CVC staff also monitor the planted trees and shrubs for a period of time until they are well-established and growing above competing vegetation like grass. Assessments help to determine maintenance activities that may be required to support the trees and shrubs early growth and establishment. Other activities may include infill planting to replace trees and shrubs that do not survive. We also conduct regular inspections as well as photo monitoring to track progress.

Rules for visiting CVC’s conservation areas can be found on our website.

Fines may be levied under the Conservation Authorities Act (R.S.O. 1990, Chapter C.27) and Regulations as well as the Trespass to Property Act (R.S.O. 1990, Chapter T.21).

To report an occurrence, please contact us at 1-800-367-0890. For urgent matter please call 911.

Over the past few years, CVC has implemented the following solutions to help address challenges at Rattray Marsh:

  • hired a Senior Specialist, Enforcement to oversee CVC’s Enforcement Program;
  • enhanced enforcement patrols during the weekdays, weekends and holidays (by CVC Security Officers and CVC Provincial Offences Officers);
  • collaborated with the City of Mississauga’s by-law enforcement for joint patrols and liaised with Peel Regional Police regarding prohibited activities occurring within the Marsh;
  • employed and supervised in-house Security Officers instead of relying on third party security companies;
  • planned enforcement blitzes, which will include the writing of Provincial Offence Notices when warranted, for prohibited activities such as, (but not limited to) dogs off leash, fireworks, remaining in conservation area after hours and camping.

CVC conservation areas may be under video surveillance for security, health and safety or research purposes. Use of any personal information collected through video surveillance is protected and restricted through the Municipal Freedom of Information and Protection of Privacy Act, R.S.O. 1990, c.M.56, as amended. Learn more about our Privacy Policy.

A series of Automated Trail Counters are deployed at entrances to Rattray Marsh, these infrared sensors count visitors entering and exiting the property and help to quantify visitation levels. While no identifying information is collected through the trail counters, this monitoring data helps CVC to more effectively plan for enforcement activities, visitor services and trail improvements, and to better understand human use of the space.

CVC has, and will continue to, identify and remove hazard trees. Hazard trees are weakened trees, that could fall and damage infrastructure (trails, roads, neighbouring properties, etc.) and pose a safety issue to staff and visitors. Further information can be found in CVC’s Sustainable Forest Management Plan (2021-2040).

Boardwalks at Rattray Marsh have been widened to support accessibility and to adhere to Accessibility for Ontarians with Disabilities Act (AODA) design of public spaces best practices. Further, the widening:

  • integrates pandemic safety considerations for social distancing
  • matches width of all other recent sections of waterfront trail boardwalks
  • better accommodates existing pedestrian load for user safety and minimizes user conflicts

CVC ecologists completed an environmental impact assessment for the Waterfront Trail Boardwalk Replacement project, spanning from June to August 2021. The assessment reviewed all available natural heritage data for the area and included a site investigation. The conclusions of the assessment informed trail corridor placement and mitigation measures to protect species and their habitat in the vicinity, this included:

  • avoidance of Cattail Organic Shallow Marsh community
  • elevation of boardwalk to avoid flooding impacts
  • avoid activities interfering with migratory timing windows, for example tree removals prior to end of March
  • minimize access areas and protect site from entrance during construction window
  • confirmation that the route avoids rare and uncommon plant species
  • monitor during construction
  • restoration, with native species, of old boardwalk trail corridorProject screening with the Ministry of the Environment, Conservation and Parks (MECP) regarding potential Species at Risk (SAR) impacts was completed in September 2021. Project given clearance to proceed on the basis of mitigation measures proposed (above).

All planned boardwalk trail improvements are now complete, and no further construction is anticipated in the near term.

Region of Peel construction work on the new pump station at the Silver Birch entrance is currently underway. The trail access from Silver Birch is closed to the public. Please use an alternate access to the conservation area. For inquiries about this project, please contact the Region of Peel at [email protected].

Giving Back to Rattray Marsh

The Rattray Marsh Protection Association was formed in 1979 and has been integral to the area’s long term protection and appreciation. Comprised of local residents and community members, RMPA is dedicated to ensuring that the community and its visitors benefit from quality educational, interpretive and stewardship opportunities at Rattray Marsh Conservation Area.

Donations in support of Rattray Marsh are accepted through CVC’s charitable partner, the CVC Foundation, a registered environmental charity.

To make a secure online donation please visit: cvcfoundation.ca

Scroll to Top