If you’ve spotted a bird exhibiting signs of illness, particularly with its eyes, you might be wondering how to report it and what the implications are. For participants in Project FeederWatch, observing and reporting diseased House Finches is a crucial part of their standard count entry. It’s equally important to note when you’ve looked for signs of disease but found none. By indicating you searched for the infection and entering “0” for the number of infected birds, you contribute vital data that helps track the disease’s spread, including areas where it has not yet appeared.
Clinical Signs of Conjunctivitis
Conjunctivitis in birds typically manifests as red, swollen, or runny eyes, often with crusting. In severe cases, the eyes can become swollen shut or so crusted over that the bird essentially loses its sight. Birds in this condition struggle to feed, and you might observe them staying on the ground beneath feeders, attempting to find seeds. When an infected bird dies, it’s usually not directly from the conjunctivitis itself, but rather from secondary causes such as starvation, exposure, or predation due to their impaired vision.
Differentiating from Other Avian Diseases
While conjunctivitis presents with distinct eye symptoms, other diseases can cause similar clinical signs. Avian pox, for instance, is another common ailment affecting a bird’s eyes. This disease is characterized by warty lesions on the head, legs, and feet, though it can sometimes be challenging to differentiate from conjunctivitis. Avian pox spreads through insect bites, direct contact with infected birds or contaminated surfaces like feeders, or ingestion of tainted food or water. Similar to conjunctivitis, infected birds become more vulnerable to predation, starvation, or environmental exposure.
The Cause of Mycoplasmal Conjunctivitis
Despite the prominent eye symptoms, the disease known as Mycoplasma gallisepticum is primarily a respiratory infection. This specific strain of bacterium is a common pathogen in domestic turkeys and chickens. Importantly, the infection poses no known health risk to humans and had not been documented in songbirds prior to its emergence. Researchers are actively investigating the transmission, genetics, and progression of this disease.
Geographic Spread and Origin
Conjunctivitis was first identified in House Finches during the winter of 1993-94 in Virginia and Maryland. Subsequently, the disease spread to states along the East Coast and has since been reported across much of eastern North America, extending as far north as Quebec, Canada, south to Florida, and west to California. It has also been observed in bird species beyond House Finches. Your continued participation in Project FeederWatch plays a vital role in documenting the ongoing evolution of this epidemic.
Other Affected Bird Species
While the disease is most prevalent in House Finches, a few confirmed cases of Mycoplasmal conjunctivitis have been reported in other species, including American Goldfinches, Purple Finches, Evening Grosbeaks, and Pine Grosbeaks. These species all belong to the Fringillidae family.
Susceptibility of Eastern House Finches
Eastern House Finches may have been the earliest victims of this disease due to their origins. House Finches are not native to eastern North America; their presence there dates back to the 1940s when some birds were released into the wild in the East after illegal pet trade sales ceased. These introduced birds established breeding populations and spread rapidly. Because the current eastern House Finch populations are descended from a small founding group, they exhibit low genetic diversity and are highly inbred, potentially making them more susceptible to diseases compared to native eastern bird species.
Factors Contributing to Rapid Spread
The rapid dissemination of the disease among House Finches can be attributed to several factors. The large population size and the tendency for these birds to gather in mobile foraging flocks mean that infected individuals frequently introduce the disease to new areas. Furthermore, some infected birds survive the illness, increasing the likelihood of transmission to others. Current evidence also suggests that infected birds do not develop long-term immunity to subsequent infections.
Role of Bird Feeders in Disease Transmission
Concentrating birds in a small area, such as at feeders, naturally increases the risk of disease transmission within that population. However, feeding birds does not necessarily accelerate the overall rate of disease spread and may not have a significant net negative impact on the House Finch population. Data from the House Finch Disease Survey indicate a decrease from epidemic levels, with the disease now affecting a smaller percentage of the population. While it remains a significant and harmful disease, House Finch populations are not currently facing an extreme risk of widespread decline. Nevertheless, responsible bird feeding practices, including regular feeder cleaning, are always recommended, even in the absence of visible disease.
Action When Observing Diseased Birds
If you observe a bird with conjunctivitis, the recommended course of action is to temporarily remove your feeders and clean them thoroughly with a 10% bleach solution (one part bleach to nine parts water). After allowing them to dry completely, re-hang them. It is also advisable to rake the area beneath the feeders to remove old seed and droppings.
Handling Infected Birds
Under the law, only licensed professionals are permitted to handle most wild birds. While it is technically possible to treat finches with conjunctivitis, it is strongly advised not to add medications to bird seed or baths. There is no reliable way to ensure that medication is effective in uncontrolled settings, and such treatments could potentially exacerbate disease spread by allowing infected birds to survive longer. Moreover, antibiotic treatment might contribute to the rapid evolution of new disease strains that could potentially affect other songbirds.
Bird-Feeding Guidelines for Healthier Flocks
- Space feeders adequately to minimize crowding among birds.
- Clean feeders regularly using a 10% bleach solution (1 part bleach to 9 parts water). Ensure any accumulated dirt around the feeding ports is removed. Allow feeders to dry completely before re-hanging them.
- Maintain the area below feeders by raking to remove droppings and old, moldy seed.
- If you notice one or two birds exhibiting signs of illness, take down your feeders and clean them meticulously with a 10% bleach solution.
