The Muscovy duck (Cairina moschata) is a large duck native to Mexico, Central America, and South America. In recent years, feral Muscovy duck populations have become established in certain areas of the United States, particularly in Florida, Texas, and parts of California. While Muscovy ducks can make interesting backyard pets, wild Muscovy ducks are often considered a problematic invasive species due to their disruptive behavior, aggressiveness, damage to property, and potential to spread disease. Understanding the key issues surrounding feral Muscovy ducks is important for finding solutions to manage their growing populations.
Where did the feral Muscovy ducks in the US come from?
The growing number of feral Muscovy ducks in the US stems from a combination of escapes and intentional releases. Some Muscovy ducks have escaped from farms and backyard enclosures over the years. However, many Muscovy duck populations, particularly in Florida, appear to have originated from intentional releases. In the 1970s-1980s, some Muscovy ducks were released into the wild by individuals hoping to establish wild breeding populations for hunting or to control mosquito populations. The Muscovy duck is a highly adaptable species that thrives in warm climates, making Florida an ideal environment for escaped and released Muscovy ducks to establish growing wild populations.
Why are Muscovy ducks considered a problematic invasive species in parts of the US?
While the Muscovy duck is a unique and interesting bird, feral Muscovy ducks cause several notable problems that have led them to be considered invasive pests in many areas:
Aggressive behavior
Muscovy drakes can become very aggressive, especially during breeding season. They will chase and attack other birds as well as pets, children, and adults. Their sharp claws can cause injuries.
Property damage
Muscovy ducks are known to damage gardens, landscaping, roofing, and other property as they fly, walk, and nest. Their feces can also stain or damage structures and vehicles.
Noise nuisance
Muscovy ducks produce loud hissing, panting, and grunting vocalizations that can become a nuisance in residential areas.
Disease spread
Muscovy ducks can potentially spread diseases to people, pets, and native wildlife since they often inhabit urban areas. Diseases of concern include avian influenza viruses.
Displacement of native birds
In some areas, large Muscovy duck populations take over habitat used by native ducks and other waterfowl. They compete for resources, and the aggressive males will mate with females of other species. This can displace native birds over time.
What areas of the US have issues with feral Muscovy ducks?
The top areas facing issues with feral Muscovy duck populations include:
Florida
Florida has the largest Muscovy duck population in the US, found widely across the state in urban and suburban areas as well as wetland habitats. Estimates suggest over 100,000 feral Muscovy ducks live in Florida. They cause numerous complaints due to aggressive behavior towards people and pets, traffic hazards, noise, and messy droppings.
Southern California
In Southern California, rapidly growing populations of feral Muscovy ducks have been documented since the 1990s after escapes and releases from farms. They are now found in urban parts of Los Angeles, San Diego, Riverside, San Bernardino, Orange, and Imperial Counties.
Southern Texas
Coastal urban areas and waterways around Corpus Christi, Houston, and the Rio Grande Valley have problematic Muscovy duck populations stemming from intentional releases and escapees.
New York
Feral Muscovy ducks have been reported in New York City and on Long Island since the 2000s after escaping captivity or being abandoned. Sightings occur near Prospect Park, Rego Park, and Flushing Meadows Park.
What human health risks do Muscovy ducks pose?
While not a major risk, Muscovy ducks can potentially transmit some diseases to people through contact with their droppings, feathers, or surfaces they contaminate. Potential health risks include:
Salmonellosis
Salmonella infection can cause diarrhea, fever, and abdominal cramps in people. Muscovy duck feces may contain Salmonella bacteria.
Avian influenza
Some strains of bird flu viruses, such as H5N1 or H5N2, can occasionally spread from wild waterfowl like Muscovy ducks to humans. This can cause serious respiratory infection.
Duck viral enteritis
This contagious herpesvirus of ducks can spread to people through direct contact with infected ducks, causing flu-like symptoms.
Dermatitis
Prolonged exposure to Muscovy duck feathers or droppings can cause skin rashes or irritation in sensitive individuals due to allergens, fungus, or parasites.
Overall, the risk of zoonotic disease transmission from Muscovy ducks is low. But care should be taken during any direct contact, especially for immunocompromised individuals. Problems arise when large urban Muscovy populations lead to increased human exposure.
What diseases can Muscovy ducks spread to other birds or animals?
Muscovy ducks can potentially spread a number of infectious diseases to other birds, pets, farm animals, and wildlife through direct contact or environmental contamination:
Duck viral enteritis
This highly contagious herpesvirus is common in Muscovy ducks. It spreads rapidly and can cause high mortality in domestic and wild waterfowl.
Avian botulism
Improper wetland management leading to boggy, oxygen-deprived conditions allows this paralytic toxin produced by bacteria to accumulate to hazardous levels in the environment. Dabbling ducks are highly susceptible.
Avian influenza
Certain H5 or H7 influenza A virus strains can cause severe illness with high mortality rates in domestic poultry as well as wild waterfowl. Migratory birds may also disseminate viruses through Muscovy populations.
Avian cholera
This contagious bacterial disease transmitted through contaminated food or water can affect many wild waterfowl species with occasionally massive die-offs.
Avian pox
Mosquito transmission can spread this viral infection characterized by wart-like lesions to a variety of birds, including ducks, geese, and swans.
Proper flock management, biosecurity measures, habitat protection, and vaccination of domestic ducks can help control spread of these diseases. Eliminating unwanted contact between Muscovy ducks and other birds may help reduce transmission risks in problematic areas.
How do communities manage problems caused by feral Muscovy ducks?
Different strategies are used to mitigate problems caused by feral Muscovy ducks:
Discouraging feeding
Laws prohibiting feeding often seek to disperse Muscovy ducks that congregate in areas. However, feeding bans are challenging to enforce.
Habitat modification
Removingduck-friendly features may disperse them from problematic sites. This can include managing pond algae, restricting shoreline vegetation, using rock barriers, or installing mesh netting to block access.
Hazing/harassment
Noise makers, lasers, balloons, sprinklers, and other aversive methods may be used to frighten Muscovy ducks away from locations. Their long-term effectiveness is variable.
Egg removal/addling
Destroying eggs by shaking, puncturing with a pin, or oiling them reduces hatch rates. But the ducks will continue laying replacement clutches.
Translocation
Capturing and relocating the ducks is costly and largely ineffective since they often return or settle in new problematic sites.
Lethal removal
As a last resort, some communities allow lethal control of Muscovy ducks by shooting or live capture followed by euthanasia. But new ducks will likely replace any that are killed.
What legislation has been proposed to allow for greater control of invasive Muscovy ducks?
Lawmakers have attempted to pass various state and federal laws aimed at allowing more aggressive control or eradication of non-native Muscovy ducks:
Federal Invasive Muscovy Duck Eradication Act
This failed 2017 bill would have directed the US Department of Agriculture to establish a program for eradicating invasive Muscovy ducks.
Texas Senate Bill 876
This 2021 bill sought to classify free-ranging Muscovy ducks as an invasive species not protected by state law. It did not pass.
Florida House Bill 1127
This successful 2018 law allows Florida’s Fish and Wildlife Conservation Commission to establish a research program studying control and eradication methods for invasive Muscovy ducks.
California Assembly Bill 1151
This 2021 bill proposes defining Muscovy ducks as an invasive species not protected by California law. It is currently under legislative review.
While declaring them an invasive or unprotected species would make control efforts easier, major eradication campaigns based on lethal removal still face opposition from some animal rights groups.
Conclusion
Feral Muscovy duck populations have become problematic across parts of the southern and coastal US due to intentional releases and escapees establishing growing wild populations. Their aggressive behavior, noise, environmental contamination, and potential spread of diseases have made them a concern, especially in urban areas. Communities have experimented with various control measures including feeding bans, habitat modification, and egg removal. But substantial eradication is unlikely without declaring them an unprotected invasive species subject to expanded lethal control methods, which remains controversial. Ongoing research seeks effective and balanced solutions for addressing invasive Muscovy duck issues. Careful management of Muscovy duck ownership, including wing clipping and containment measures, is crucial for preventing further escapes that worsen feral populations. Overall, the problematic nature of invasive Muscovy ducks stems from irresponsible introductions and ownership combined with their adaptive abilities to thrive and breed aggressively across warm regions.