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 along the Lake Ontario 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.

In the summer of 2022, CVC will conduct breeding bird surveys, as a follow up from 2014, to assess the bird community at Rattray Marsh. In 2014, CVC collected baseline breeding bird data in areas that would be affected by the emerald ash borer infestation. CVC will repeat these surveys in 2022 to determine how the bird community has changed during that time.

Beginning in 2008, Mississauga saw a widespread infestation of native ash trees due to an invasive beetle called the emerald ash borer (EAB). These forest pests have 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.

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

Since 2010, CVC has planted over 8,000 native trees and shrubs at Rattray Marsh, with another 1,000 trees and shrubs being planted in 2022 . 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.

Before 2014, upstream development around Sheridan Creek had negatively affected the marsh by contributing excess sediment, burying the native marsh ecosystem. This resulted in poor water quality and low water levels due to sediment accumulation. Beginning in 2013, CVC removed the excess sediment from the Marsh, which has benefitted the bird community. Least bittern, a species at risk bird, has benefitted from this since they can only feed within the cattails. As a result, more habitat has become available to them. Visitors to Rattray Marsh have noticed their presence, with more observations in citizen science platforms like eBird.

Since sediment removal, cattails have become less dense allowing more water to flow between them. This has improved habitat for wildlife such as fish, turtles, frogs and crayfish in the marsh.

No. This species lives in the boreal forest. The public should not expect to see them regularly at Rattray Marsh. They only very rarely come down to Southern Ontario in the winter when food sources (i.e., rodents) are low. The last known recorded sighting at Rattray Marsh was in the winter of 2004/2005.

CVC has records of great horned owls nesting at Rattray Marsh within forested habitat. However, their abundance will always be low since a nesting pair occupies a huge area. This species does not generally reuse nests. If a nest is observed in one year and then empty the next year, it means the bird moved onto a new nest somewhere else, which may or may not be within Rattray Marsh Conservation Area. Great horned owls do not build their own nests, but use old nests mainly made by other birds of prey. CVC does not remove trees with old nests of birds of prey, and tree cutting should not affect their ability to find new nesting spots. The most recent recorded sighting of a great horned owl at Rattray Marsh was on October 5, 2021.

This species can be found at Rattray Marsh all year long since they are non-migratory. They use forested habitat with some openings in the canopy, which Rattray Marsh has. The most recent recorded sighting of eastern screech-owls was on January 31, 2022 and a local neighbour of the marsh reported that a pair of eastern screech-owls is currently nesting in a nest box on their property.

This species breeds at Rattray Marsh and also passes through during spring and fall migration. They use open woodland habitat and forest edges, which Rattray Marsh has. The most recent recorded sighting was on February 18, 2022.

This species breeds at Rattray and also passes through during spring and fall migration. They’re found along forest edges or fields that have some scattered trees, often in areas near water. The most recent recorded sighting was on September 9, 2021, during migration.

This species breeds at Rattray and also passes through during spring and fall migration. This species uses open deciduous, conifer or mixed woodland habitats near water, which the Rattray Marsh Conservation Area has. They tend to like fruit-bearing trees and shrubs which CVC continues to actively plant. The most recent record sighting was on February 7, 2022.

This species is seen regularly at the marsh feeding on fish during breeding and spring and fall migration. We do not have any records of them nesting on the property now or in the past. However, this species is colonial, and are selective in their habitat for nesting. They tend to avoid areas with a lot of humans and mammalian predators. The most recent recorded sighting was on November 30, 2021.

This species can be seen at Rattray Marsh throughout the year, especially during spring and fall migration. None of CVC’s records indicate they nested on the property, however many external records show they use the property to feed in. Although the Rattray Marsh Conservation Area is suitable for them to nest in, the data shows they’re using it for feeding and during migration. The most recent recorded sighting was March 14, 2022.


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


Deer prefer open habitat. The emerald ash borer infestation and felling of dead or dying ash trees has opened up the tree canopy, making the open space more attractive to deer. Newly planted trees and shrubs that are needed for the forest to regenerate are threatened by grazing deer.

If left unchecked, a significant portion of CVC’s new deciduous tree and shrub plantings will be destroyed. If the planted trees and shrubs are not protected and allowed to establish (where most of a tree’s foliage and branches are above the reach of deer) we risk losing the new plantings, which will result in a re-invasion of non-native plants and return of low-quality habitat.

Early efforts to apply natural deer deterrents have not prevented heavy grazing by deer, leading to stunted growth and significant tree mortality.

We are currently testing the use of temporary fences around pockets of new deciduous trees and shrubs that are being heavily impacted by deer. These fences will be left in place for approximately five years until the trees are tall enough that most of their branches/foliage will not be impacted by deer. It also allows shrubs to establish and grow large, healthy branches and foliage that can better withstand deer grazing and regenerate rapidly afterward. Deer exclosure fencing has decades of research and application in Ontario and the northeastern U.S. It has proven to be the most effective way to ensure survival of planted and naturally regenerated plants in areas where deer can have a significant impact.

The temporary fencing will not impact the movement of wildlife through the conservation area. The fence mesh size allows small mammals, reptiles and amphibians to pass through. The fencing will have strips of blue flagging tape tied to it to increase visibility to wildlife. Areas between fencing will continue to regenerate with planted trees, shrubs and natural cover that will provide forage and cover for wildlife.

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, 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 common carp cause significant harm to wetland health.

Several techniques to exclude carp were assessed through the EA (i.e. fencing, construction of berms or weirs). Fencing was chosen due to its effectiveness, the ease of replacement, smaller footprint and level of impact.

Common carp typically enter the marsh in mid-May (when water temperature approaches 19° C). Fencing is strategically installed in portions of the restoration areas to exclude carp from open water. Carp continue to have access to Sheridan Creek and the central portion of the marsh.

Early results indicate a reduction in carp numbers and persistence of aquatic vegetation based on monitoring by Canadian Wildlife Service (CWS), indicating that carp exclusion fencing is effective.

CVC periodically inspects and maintains the fencing to fix underwater breaches or toppled portions to the fence provided water levels allow a safe working environment.

Breaches in the fencing can occur when water levels in the marsh become extremely high; for example, when the outlet to Lake Ontario is closed or during flood events. In these instances, water can over top the fence. The pressure of flowing water can also knock down portions of the fence. Carp are large burrowing fish and may also be able to dig under 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.

Removing fencing will allow common carp to access the restored marsh, severely compromising restoration efforts and the overall health of Rattray Marsh.

Without fencing, impacts will include decreases in fish and aquatic plant diversity reductions in water quality. This would undo the benefits of costly restoration efforts that took place from 2005-2019.

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 2022, black filter cloth will be incorporated into the fencing to provide a 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).

Conservation Area Management Activities

Rattray Marsh has experienced severe ecological degradation over the years, due to:

  • Development in Sheridan Creek resulting in excessive amounts of sediment entering Rattray Marsh.
  • Urbanization around Rattray Marsh affecting its overall health.
  • Invasive nonnative species and native species with no natural enemies to keep populations in check.
  • Degraded water quality.

CVC is committed to the protection of wildlife and wildlife habitats 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 landmark in the community.

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

  • Park Planning and Zoning: CVC is guided by its Conservation Areas Master Strategy.
  • Ecosystem Restoration: Over a century of land clearing, agriculture and urban development buried Rattray Marsh’s organic soils under a metre of sediment. CVC removed that sediment from the marsh (2014-2015) to restore Rattray Marsh to a healthier sustainable ecosystem.
  • Invasive Species Control: Non-native carp from Lake Ontario 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. Since 2010, CVC has planted over 8,000 native trees and shrubs at Rattray Marsh, with another 900 trees and shrubs being planted in 2022. 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: Trails are directed away from environmentally sensitive areas to protect wildlife. Elevated boardwalks protect sensitive soils and allow for the movement of wildlife underneath. Handrails are used to prevent people and pets from wandering off trails and disturbing wildlife and their habitat.  To learn more about our trail renovation work at Rattray Marsh, please visit our Rattray Marsh Conservation Area Trail Renovation Project.
  • Sustainable Infrastructure Development: Infrastructure proposals are reviewed by CVC Ecologists to determine the best way to avoid, minimize and mitigate disturbances to wildlife and vegetation. For example, boardwalk construction is done outside of the bird breeding window to avoid disturbing them during this critical period.
  • 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.
  • Monitoring the marsh after sediment removal began in 2015 with regular monitoring continuing each year. Bi-weekly monitoring is continuing in 2022, starting April 7th. Indicators include aquatic vegetation, sediment, photo monitoring, as well as assessing and repairing carp control fencing as needed.

Rules for visiting CVC’s conservation areas can be found here.

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 two 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 3rd 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 held an enforcement blitz this spring at Rattray Marsh Conservation Area where staff dedicated 51 hours patrolling the property over the course of a week. Provincial Offences Officers, Security Officers and City of Mississauga By-Law Officers dedicated their time to educate visitors on the importance of dog off-leash compliance.

Our staff observed a 96 per cent compliance rate during the enforcement blitz through contact with 160 dogs and only 7 off-leash encounters. Visitors were respectful and CVC enforcement staff did not experience negative encounters due to off-leash activity. All instances where non-compliance occurred (7 dogs off-leash and 3 bike riding), were corrected in a timely and positive manner as our staff educated and provided warnings to those visitors.

CVC staff will continue to monitor and engage with visitors to encourage compliance. We thank all visitors for continuing to respect the rules and regulations at Rattray Marsh Conservation Area. Your efforts help protect the wildlife and sensitive habitat at the property.

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.

CVC has and will continue to identify and remove hazard trees, defined as 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)

An environmental impact assessment for the Waterfront Trail Boardwalk Replacement project was undertaken by qualified CVC ecologists in June – 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:

  • Avoidance of Cattail Organic Shallow Marsh community
  • Elevation of boardwalk to avoid flooding impacts
  • Avoid activities interfering with migratory timing windows (i.e. 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 corridor

Project 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).

Notice of the trail construction work can be found here.

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 recently upgraded the information kiosks, wayfinding and navigational signage at Rattray Marsh in accordance to our standardized Conservation Area Signage Plan (applies to all CVC owned and managed properties).  At Rattray Marsh, signage about cycling is provided at all entrances and on some of the wayfinding posts along the trails.

CVC has no plans to install further regulation signage at Rattray Marsh.

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