Photo by D. Sillman
(Click here to listen to an audio version of this blog … Bird Feeders and Bird Baths
Five years ago, I wrote about Helen MacDonald’s (the author of H is for Hawk (2014) and Vesper Flights (2020)) January 6, 2016, N.Y. Times article entitled “Why do we feed wild animals?” The primary motivation, according to MacDonald, that leads us to spend three billion dollars a year on wild bird feed, is that by feeding the birds around us we begin to feel like we are a part of their natural world! ! As MacDonald wrote so eloquently, feeding wild animals “surrounds us with creatures that know us, are able to forge bonds with us, have come to regard us as part of their world.”
Now there are good consequences and bad consequences when the animals have humans as their worldly companions. With expanding food sources latitudinal ranges can be expanded (as we have previously discussed for North American cardinals (Cardinalis cardinalis) and goldfinches (Spinus tristis)), migration routes (and all of the stresses and dangers associated with migration) can be shortened and lessened (as we have noted for the Eurasian blackcap (Sylvia atricapilla), and spring breeding health and nestling vigor and survival can be improved (as we have discussed for a population of Wisconsin, black-capped chickadees (Poecile atricapillus)).
Eurasian blue tit, Photo by F.C.Franklin, Wikimedia Commons
We also have seen, though, that the reproductive successes of feeder fed vs. naturally fed birds can be quite different if the provided bird seed is poor in nutritional quality (i.e. excessively high in fat and low in protein with low levels of essential nutrients). Observations made in a study in England on the blue tit (Cyanistes caeruleus) and the great tit (Parus major) (two European relatives of the chickadee)) revealed that feeder fed birds laid fewer eggs, had fewer fledges and had significantly reduced overall levels of reproductive success. These high fat-low nutrient bird seed sources are often referred to as “avian junk food,” and the overall health and vigor of the junk-food-fed birds is often quite poor.
This past spring and summer there were a number of warnings from federal and state government wildlife authorities and also from the national and state-based Audubon Societies in a number of eastern states that advised people to stop feeding their backyard birds and to take down their feeders and their bird baths! The feeding bond between humans and birds had to be broken to save the birds from a raging epidemic.
There was a disease affecting many species of song birds that caused their eyes to become swollen and crusty and also caused many of them to become disoriented. Affected birds were crippled by muscle spasms and many, eventually, died. Dead birds were often found in large numbers! The first sick birds were seen in the Washington, D.C. area in April, but reports of more affected birds quickly came in from Maryland, West Virginia and Virginia. By June, there were sick birds in Delaware, New Jersey, Ohio, Tennessee, Florida, Indiana and Pennsylvania!
Bodies of dead birds were sent to a number of specialized labs for detailed analysis. Tests looking for a wide range of fungal and bacterial toxins, viruses and even sexually transmitted, avian-diseases were conducted. These tests eliminated a long list of known avian disorders (including West Nile virus, avian influenza, Newcastle disease, herpesviruses, poxviruses, salmonella, chlamydia and trichomonas) but did not, definitively, find a cause to the current epidemic.
Male house finch (healthy!). Photo by J. Benson, Wikimedia Commons
The eye symptoms of this 2021 disease outbreak reminded many researchers and bird lovers of the house finch eye disease epidemic of the early 1990’s. Infected house finches developed crusty, swollen eyelids which in some birds led to blindness and death due to starvation or increased vulnerability to predation. This outbreak was caused by a highly infectious bacterium (Mycoplasma gallisepticum) that was passed from finch to finch. The house finch eye disease spread all the way across North America in less than a decade and decimated house finch populations. The house finch eye disease outbreak, like the 2021 disease event, was concentrated in birds that gathered near bird feeders to eat, The house finch eye disease, though, did not have the severe neurological symptoms seen in the 2021 disease event. Also, the mycoplasma infection was confined to house finch populations while the 2021 disease affects many species of birds (including blue jays, European starlings, northern cardinals, American robins and common grackles). Nestlings and fledglings are particularly vulnerable to this 2021 disease.
Periodical cicada. Photo by M. O’Donnell Flickr
Many theories have been proposed to explain this new disease. One examines the correlation both in time and also in geography of infected birds and the emergence of the Brood X periodical cicadas. It is widely known that many of the emerging 17-year cicadas are heavily infected with a pathogenic fungus (the so called cicada “zombie” fungus) which they pass along not only to other emerging cicadas but also to the eggs (and, then, subsequent brood population) of their cicada cohort. There is, though, no specific evidence that this fungus is the cause of the newest avian epidemic although it is interesting that the most frequently infected bird species are also those birds that are most likely to consume the periodical cicadas. Both state and private authorities recommended removing backyard bird feeders and bird baths in those counties which were most affected by the disease. This avian “social distancing” was intended to keep birds from congregating and passing along infections. Feeder and bird bath removal (and rigid cleaning regimes) were quite effective in slowing the spread of the house finch eye disease 25 years ago. It was recommended that feeders and bird baths be removed in Kentucky, Maryland, Virginia, West Virginia and Pennsylvania and vigorously cleaned (with disinfecting bleach solutions) everywhere else.
Photo by D. Sillman
In early August, authorities, like the Pennsylvania Game Commission and the Audubon Society of Western Pennsylvania, rescinded their feeder and bird bath removal advice. The cause of the spring and early summer disease outbreak has still not been determined, but the epidemic seems to have passed. This sudden outbreak and equally sudden disappearance of infections adds some credibility to the periodical cicada, “zombie” fungus hypothesis but to date, no definite link to the fungus and ocular-neurological avian disease has been established.
So, something happened to our birds this past summer, and we don’t know what it was! To be safe, we need to recognize that birds (like people) live in a world teeming with viruses, and that some of these are capable of causing great harm! We all need to remember to keep our bird baths and bird feeders clean and keep our feeders well stocked with high quality seed! Let’s be conscientious members of our surrounding natural community!