Netley-Libau Marsh (MB009)

Netley-Libau Marsh (MB009)

Libau, Manitoba

Description du site

Netley-Libau Marsh is situated at the south end of Lake Winnipeg, where the Red River branches several times and empties into the lake. Wave action on Lake Winnipeg, particularly due to strong wind-assisted tides, has produced a small beach ridge at the lakes south end, which acts as a barrier separating parts of Netley-Libau Marsh from the lake. The Red River is an important force of change in the large network of wetlands found here. Due to its history of frequent flooding, the route of the main channel of the river has changed numerous times. The area is very flat, and consists of many small bodies of water connected by channels and is interlaced with fingers of grassland, trees and shrubs.

The marsh is split into two distinct wetland complexes either side of the Red River: Netley Marsh on the west and; Libau Marsh on the east. Netley Marsh is surrounded by cottages and cropland whereas the Libau Marsh, which includes part of the Brokenhead Ojibway Nation reserve, is surrounded primarily by haylands and cattle pasture. The Libau Marsh is less accessible than the Netley Marsh. The northeast edge of the marsh includes part of the Patricia Beach Provincial Park.

Oiseaux

Netley-Libau Marsh is best known for its tremendous concentrations of southward-migrating birds. Numbers of geese and ducks on some occasions exceed 100,000 during fall migration. A little earlier in the year, at least 25,000 moulting ducks are found in the area. Red-winged and Yellow-headed blackbirds congregate here in late autumn in numbers exceeding 100,000. The globally vulnerable Rusty Blackbird also arrives during this period, swelling the total number of blackbirds. As well, at the beginning of the fall migration in August, swallows are found here in the thousands.

In addition to the numerous species that stopover at the site during fall migration, several bird species breed at this site in significant numbers. Franklins Gulls nest in large colonies within the marsh, in numbers exceeding 4,500 pairs. Species that breed in large, though not significant numbers at the site include Forster’s Tern (325 nests in the 1970’s), Black-crowned Night Heron (100 pairs), the Eared Grebe (100+ pairs) and the Western Grebe (125+ pairs). At least twelve species ducks breed here mostly dabbling ducks.

Enjeux de conservation

The portion of the site around Hardman Lake, which is between the main channel and west channels, is the Netley Marsh Game Bird Refuge, created in 1966 to improve hunting by providing a refuge area for migratory game birds; the whole Netley-Libau Marsh site has been designated as a Manitoba Heritage Marsh. Recreation is the main use of the inner delta, while the main channels see much use by sport fishermen. This occasionally leads to disturbance of nesting birds. An important commercial minnow fishing industry occurs here. Broken fishing line may also be responsible for entangling piscivorous birds such as pelicans in this area.

Because the water levels of Lake Winnipeg are regulated by Manitoba Hydro, the physical structure of the marshes has been altered, leading to the loss of wetland habitat. Part of this change can be seen in the number of water bodies comprising the marsh: in 1960 there were 50 individual waterbodies, whereas in 1980 the number had decreased to 17. The control and maintenance of water levels also means that natural drawdowns, which encourage new plant species, are eliminated. Large floods that sweep through the Netley Marsh are a natural phenomenon that occur from time to time. These floods tend to discourage development such as urbanization and agriculture.

A small channel was opened in the banks of the Red River in the 1920’s, allowing boat access to the Netley Marsh from the river. The area of marsh, now known as Netley Lake, is subject to large scale changes with water flowing directly from the river. The ‘Netley Cut’ has a width of around 400m and the banks continue to be subject to erosion. A cross-border partnership has been established in the area seeking solutions to the long-term degradation of the marsh. Although large-scale ecological restoration remains unlikely, experimental solutions are being sought to re-establish emergent vegetation on the Netley Marsh.

Other threats to the area include Purple Loosestrife, this site having the provinces largest infestation, and carp, which destroy marsh vegetation thereby removing food sources for some duck species. Rainbow Smelt and Zebra Mussels are also concerns at this site.

Catégories ZICO Habitats Usages Menaces Potencielles ou Existantes Status de Protection

• Quiscale rouilleux250 (max.)
• Pie-grièche migratrice1 (max.)
• Oiseaux aquatiques100 000 (max.)
• Mouette de Franklin9 000 (max.)
• Mouette de Bonaparte3 000 (max.)