Eurasian collared doves are an invasive species that has rapidly expanded its range. Originally from Europe, Asia, and northern Africa, these birds are medium to large-sized with pale sandy-gray plumage and a distinctive black half-collar on their neck. Their adaptability facilitated their widespread establishment, notably after their introduction to the Bahamas in 1974, leading to their swift colonization of Florida by the 1980s and subsequent spread across much of North America. This rapid population growth and broad dispersal often lead to negative consequences for local ecosystems and human interests.
Ecological Competition
Eurasian collared doves compete with native bird species for essential resources, impacting local ecosystems. They primarily forage on the ground, consuming seeds, grains, berries, and insects. Large flocks can gather at feeding sites, aggressively defending these food sources and discouraging other bird species from accessing them.
The doves also vie for suitable nesting locations, utilizing trees, shrubs, and human-made structures. Their nests are flimsy platforms constructed from sticks, which they can build rapidly. In warmer climates, their ability to nest year-round contributes to their reproductive success and competitive advantage.
Eurasian collared doves exhibit a territorial nature, often chasing away native birds such as Mourning Doves, cardinals, and Blue Jays. Instances include the usurpation of American Robin nests, where collared doves aggressively displaced the native occupants. This aggressive behavior, combined with their high reproductive rate, poses a threat of displacement for native bird populations, leading to concerns about local biodiversity reduction.
Agricultural Damage
Eurasian collared doves cause economic problems within the agricultural sector through their feeding habits. These birds consume valuable crops, particularly grains such as corn, wheat, sunflower seeds, millet, and milo, both in cultivated fields and in storage facilities after harvest. Their presence in large flocks can lead to substantial destruction of crops.
The impact of this crop consumption can result in significant financial losses for farmers. Damage to fruit crops, including sweet cherries, blueberries, wine grapes, and apples, can be severe, with some crops experiencing up to 31% yield loss if not managed. Annually, the economic impact of bird damage to agriculture can amount to millions of dollars in affected regions.
Beyond direct consumption, Eurasian collared doves contribute to the contamination of food stocks. Their presence and droppings can lead to physical and microbiological contamination of agricultural products. This affects the quality and marketability of yields.
Disease Transmission
Eurasian collared doves can carry and transmit various diseases, posing health risks to other bird populations and livestock. They are known carriers of the protozoan parasite Trichomonas gallinae, which causes trichomonosis, also referred to as canker or roup. This disease leads to inflammation in the oral cavity, throat, crop, and esophagus, making it difficult for infected birds to eat and often resulting in starvation or death.
The parasite can spread through contaminated food and water sources, such as bird feeders, and also via predators consuming infected doves. While Trichomonas gallinae is not dangerous to humans, cats, or dogs, it can significantly impact other bird species. Eurasian collared doves also carry Pigeon paramyxovirus type 1 (PMV-1), which presents an economic threat to domestic poultry.
These doves are frequently infected with West Nile virus (WNV), and they can infect mosquitoes. This makes them reservoirs for the virus, particularly in areas where their populations are abundant. Other diseases like avian pox, Salmonella, and Chlamydia psittaci have been associated with Eurasian collared doves, highlighting their role in pathogen circulation that can affect vulnerable native bird species and domestic animals.
Nuisance Issues
In urban and suburban environments, large populations of Eurasian collared doves create several nuisance issues for residents. Their persistent cooing can result in noise pollution, particularly during breeding displays and in the early morning hours. This constant vocalization can be a disturbance in residential areas.
The accumulation of their droppings is a common problem, leaving unsightly and corrosive stains on buildings, vehicles, and outdoor furniture. These droppings contain harmful bacteria and fungi, raising hygiene concerns. Their acidic nature can lead to structural degradation of surfaces over time. Wet droppings can also create slippery hazards on pavements.
Eurasian collared doves frequently nest in undesirable locations, such as eaves, gutters, vents, air conditioning units, or outdoor machinery. Their flimsy nests can cause blockages in drainage systems or minor structural damage to buildings. Such nesting activities can increase the presence of parasites and airborne pathogens in close proximity to human activity.