Invasive Plants and Waterfowl

By: Zach Peklo,

North Country Cooperative Invasive Species Management Area

 

Invasive species are a growing problem in northern Michigan, and the impacts could soon be seen by outdoorsmen across the area.  Invasive species are introduced, or non-native species, that cause economic, human health, or environmental problems.   Hunter awareness is an important factor in the fight against invasive species.  One published survey found that one third of hunters did not know that invasive species posed a threat to waterfowl populations.  The same survey found that half of waterfowl hunters were visiting multiple bodies of water within five days.  These hunters could unknowingly be taking aquatic invasive species with them to new locations.  Hunters have been known to move one invasive species, Phragmites, long distances by incorporating it into waterfowl hunting blinds or boats as camouflage.  In addition to never purposely transporting invasive species, it is important for outdoorsman to clean waders, boots, and boats before they leave their hunting spots.

 

Phragmites, a tall invasive grass, is likely to have a large impact on migratory waterfowl.  It quickly forms thick monocultures that force out native wetland plants.  To say a plant is growing in a monoculture means that it is the only plant growing in the area.   Besides making hunter access difficult by blocking passageways, Phragmites reduces the amount of open water on ponds and lakes needed as stop over locations for migratory birds.

 

One group of migratory birds popular with hunters are ducks.  There are two types of ducks, dabbling and diving.  A dabbling duck is typically found in shallow water and feeds mostly along the surface of the water, or by tipping head first into the water to graze on aquatic plants, larvae, and insects.  These ducks rarely dive and may stay near the shallow edges of larger waterways.  Diving ducks, also called sea ducks, are found on large, deep lakes and rivers, coastal bays, and inlets, where they dive for food.  Both types of ducks can be impacted greatly by the introduction of invasive plants.

 

Diving ducks, such as canvasback, redhead and ringneck, feed primarily on native vegetation.  Eurasian watermilfoil is an underwater, rooted, invasive plant that causes big problems in infected lakes, pushing out native plants.  Eurasian milfoil displaces an important native plant, eel grass (vallisneria americana), also called water celery or tape grass.  Eel grass is an underwater plant that is one of the most important food sources for the canvasback duck.  Canvasback populations are related to the amount of eel grass, resulting in population changes when it is displaced by Eurasian watermilfoil.  Red-heads and ring-necked ducks feed more commonly in shallow water.  There they forage on sedges, rushes, wild rice, and tender underwater plants.  The replacement of these plants with Eurasian watermilfoil and Phragmites could lead to a drop in populations of diving duck species.  These duck species build their nests with native bulrush, cattails and sedges.  Native plant species are commonly outcompeted by Phragmites and another invader, purple loosestrife—invasive species that are not suitable for nest construction due to their hard, woody stems.

 

Many dabbling ducks, such as mallards, wood ducks, and shovlers, feed on aquatic invertebrates. Aquatic invertebrates are small animals, such as insects, crustaceans, mollusks, and worms that live in water. This diet, along with native vegetation, provides them with large amounts of protein for the southern migrations. Diverse plant communities lead to high numbers of aquatic invertebrates. Invasive species reduce plant diversity by their tendency for dense growth that reduces plant diversity. This in turn leads to a reduction in the number of aquatic invertebrates. The drop in invertebrates can cause ducks to continuously move to find adequate quantities of food. This constant movement can result in poor body condition and reduced fitness. When waterfowl move northward to breed, this poor body condition can result in a drop in nest success.

 

Invasive species could have profound impacts on Michigan’s wild game species if they become established, threatening the diverse and abundant populations available to Michigan hunters.   Outdoorsman can help stop the spread of invasive species by cleaning their equipment to avoid transporting seeds.

 

To contact North Country CISMA, drop by their office at the Wexford County Court house.  They can also be reached by phone at 231-429-5072 or email at Vicki.Sawicki@nullmacd.org

Wood ducks are a beautifully colored dabbling duck. Photo credit D. C. Dister

 

Redhead ducks, a type of diving duck can be observed diving to feed on mollusks, invertebrates, and submerged aquatic vegetation. Photo credit D. C. Dister

 

Invasive Phragmites grows in tall, dense stands that push out native vegetation that is valuable to wildlife. Photo credit NCCISMA

 

Eurasian watermilfoil is an aggressive invasive plant that can displace native plants. Photo credit Graves Lovell, Alabama Department of Conservation and Natural Resources, Bugwood.org