The Last Straw

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Photo courtesy of the Wiki Commons.

By Christine Harris

Two years ago the National Park Service visitor center where I work held a public screening of the documentary film Bag It! followed by a panel discussion. Bag It! tells the story of Jeb Berrier whose decision to stop using single-use plastic bags leads him to delve into the complicated world of recycling and the impacts that plastics have on our oceans and our health. The panel discussion was to focus on recycling and plastics in our oceans.

As the panel members took their seats in front of the audience after the showing I was surprised to see a ten-year-old boy among them. The boy was Milo Cress founder of the Be Straw Free campaign. At first I thought, why focus on straws? Don’t we have bigger issues to face? Yet after hearing more from Milo about his campaign I better understood how his message fits into the much larger issues of disposable plastics and plastics in our oceans.

Straws are one of the top ten marine debris items. In 2013 COASTSWEEP, an annual volunteer-based cleanup of Massachusetts’ beaches, found straws and drink stirrers to be the fifth most common type of trash collected with over 5,100 collected during the event.

Photo courtesy of the USFWS.

An albatross with a stomach full of plastic debris. Photo courtesy of the USFWS.

In the United States 500 million disposable straws are used each day. Though most straws are made of recyclable plastics like plastic #2 or #5, plastic drinking straws present a problem for single stream recycling and most communities will not recycle them. Straws can jam up the large sorting machines used at single stream recycling facilities.

Milo Cress’ Be Straw Free campaign, which he started when he was nine years old, invites people to take the pledge to go straw free by asking for no straw when at restaurants or when getting drinks to go and by not purchasing them for use at home. For those who like to use straws he suggests buying a reusable straw. His campaign also encourages restaurants to adopt an Offer First policy. Instead of automatically giving each patron a straw restaurant employees first ask customers if they want one.

Milo, who hails from Burlington, Vermont, has brought his movement all over the country. In his hometown Mayor Bob Kiss issued a proclamation declaring the tenets of the “Be Straw Free” as best practices for the city. In July of 2013, after meeting Milo, Colorado Governor John Hickenlooper declared a statewide “Straw Free Day.” On Earth Day in 2013 Xanterra Resorts, a concessionaire responsible for running lodges and restaurants in many national parks including Yellowstone, Zion, and the Grand Canyon, partnered with Milo to bring the “Be Straw Free” campaign to their facilities.

Grand Canyon Lodge. Photo Courtesy of Wiki Commons.

Grand Canyon Lodge. Managed by Xanterra Resorts. Photo Courtesy of Wiki Commons.

Milo has also visited countless schools in the United States, Australia and Europe where he encourages schools to stop using plastic straws and raises awareness about larger issues like single use disposable plastics and plastics in our oceans. Not bad for a kid who’s twelve years old.

Restoring the Herring River

The Herring River Estuary. Photo by Christine Harris.

The Herring River Estuary. Photo by Christine Harris.

By Christine Harris

In 1908 the Herring River Estuary in Wellfleet, Massachusetts, a system supporting 1100 acres of salt marsh, was diked off, restricting normal tidal flow and eliminating all but 10 acres of the marsh. The reasoning behind the construction of the dike seems ludicrous in light of modern ecological understanding. Today an effort is being made to restore salt marshes throughout the country, including those of the Herring River Estuary.

At the turn of the twentieth century the quaint coastal town of Wellfleet, Massachusetts was becoming a popular resort area to which many wealthy city-dwellers flocked. One popular hotel, the Chequesset Inn, located near the mouth of the Herring River, attracted an elite clientele. Guests at the Chequesset, and other area establishments, enjoyed spending time relaxing by Wellfleet Harbor, but complained about the mosquitoes. At the time it was believed that the source of the mosquitoes was the Herring River, and it was thought that if the salt marshes of the estuary were eliminated, the mosquito population in the area would decrease significantly. Thus the Chequesset Neck Dike was constructed by the state in 1908, reducing the mouth of the river from a width of several hundred feet to six feet, and effectively cutting off tidal flow beyond the dike.

Cutting off tidal flow to the Herring River significantly affected the health of the ecosystem it supported. In place of native salt marsh plants the Herring River now hosts a number of invasive plant species, including a large amount of the invasive reed phragmites. Furthermore, without the flushing of the tides and the presence of saltwater minnows such as the mummichog, a type of killifish that feed on mosquito larva, the Herring River likely provides breeding grounds for more mosquitoes now than it did before it was diked off.

Once considered to provide little more than foul smells and insects, salt marshes are now recognized as biologically significant ecosystems on which many species, including humans, depend. Peat, the spongy layer of decomposing plant material which is the base of a salt marsh, has been recognized to provide a buffer from storm damage. When storm surges threaten coastlines, peat absorbs flood waters and reduces the height of these surges, protecting coastal communities from the impacts of severe flooding.

Salt marsh peat. Photo by Christine Harris.

Salt marsh peat. Photo by Christine Harris.

Another beneficial feature of salt marshes is their role as the nurseries of the ocean. Over two thirds of all commercially harvested seafood species, including shellfish, finfish, crabs, and lobsters, depend on the salt marsh for part of their life cycles. Salt marshes provide cover and camouflage for many of these harvestable species when they are young and most susceptible to predation, and provide a safe place for breeding and foraging. Salt marshes also have recreational value as popular places to fish, kayak, and contemplate the natural world.

With knowledge of the benefits which marshes provide, local communities, the state, the county and the Cape Cod National Seashore have taken on the task of restoring several previously degraded salt marsh systems on Cape Cod, including that of the Herring River. Most of these restoration projects focus on the use of gradual tidal restoration to reintroduce saltwater, along with the species of plants and animals it supports, over the course of many years.  The Herring River restoration project centers around the reconstruction of the Chequesset Neck Dike. The proposed structure would provide access to the public for fishing and boating and have a series of sluice gates that could allow for incremental tidal restoration across a width of 100 feet. Construction of the new dike is set to begin in 2016.

Wood Storks No Longer Listed as Endangered

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Wood Stork. Photograph courtesy of the USFWS.

By Christine Harris

We often hear stories of species teetering on the brink of extinction. Rarely do we hear positive news about the fate of a threatened or endangered species, but the continuing recovery of the wood stork (Mycteria americana) is one of those rare stories.

A large, bald, wading bird standing approximately four feet tall with a wingspan of five feet, the American wood stork population was drastically reduced by habitat loss and fragmentation as many of the Florida wetlands in which it bred and lived were destroyed.  This habitat loss led to a drastic population decrease from 40,000 breeding adults in the 1930s to around 10,000 in the 1970s. Today the population of breeding adults is estimated to be between 15,000 and 20,000.

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Wood Stork Florida habitat. Image courtesy of University of Florida.

The wood stork’s population increase over the past thirty years is partially due to the fact that the species has expanded its range and established breeding colonies in new areas in Georgia, North Carolina and South Carolina.  These new breeding colonies have helped the species to compensate for the loss of some of its historic nesting grounds in Florida. The wood stork has also expanded its wintering grounds to include parts of Mississippi and Alabama.

On June 26, 2014 Secretary of the Interior and former REI CEO Sally Jewell announced that the wood stork is being downgraded from an endangered to a threatened species.  Jewell made the announcement at the Harris Neck National Wildlife Refuge on the coast of Georgia where an artificial wetland created in the 1980s now harbors 800 breeding adult wood storks.  Restored and artificial wetlands throughout the wood stork’s breeding range have helped contribute to its recovery.

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Wood Storks in their habitat. Photograph courtesy of wiki commons.

Although the population has made a significant recovery, not everyone is happy about the decision to change the bird’s status from endangered to threatened.  Florida’s chapter of the National Audubon Society has publicly decried the decision citing the decline of the species in its historic range as cause for concern.  Though the species is now breeding in areas where it didn’t when it was listed thirty years ago, many of the wetlands in which it bred historically have been further destroyed or damaged since it was listed leading to a population decline in some areas of Florida.

Although some consider the status change to be premature, the protection awarded to the species under the Endangered Species Act will be virtually the same as it was when the wood stork was listed as endangered.  The downgrade to “threatened” indicates that the US Fish and Wildlife Service, the Federal agency that oversees the implementation of the Endangered Species Act, no longer considers the species to be at risk for extinction.  Thirty years ago many believed the wood stork would never see a status downgrade.  When the species was first listed in 1984 wildlife biologists feared the bird would be extinct by 2000.

 

 

Birding for All

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By Christine Harris

Innovative birding programs across the country are bringing this popular pastime to many unlikely candidates.  The stereotypical image of a “birder” to many would be a man who wears a floppy hat and a beige vest, is harnessed into a pair of binoculars and has a spotting scope slung over his shoulder. I won’t pretend that this description doesn’t apply to some of the birders I’ve encountered over the years, but as the pastime increases in popularity it has found some less-traditional enthusiasts.

The Michigan Bird Brains are a group of young birders organized by their birding mentor and teacher Donna Posont. Many youth birding groups have sprung up around the country, but what makes the Bird Brains unique is that they bird entirely by ear because they are all visually-impaired.  Donna Posont, who is also visually-impaired, teaches her students to identify birds by sound, a skill that can give them a unique advantage over sighted birders as pointed out by one of her students, seventh-grader Austin Shepherd. Sighted people can only focus on one bird at a time while Austin points out, “it’s special because we can hear lots of different birds at once.” The Bird Brains have participated in the Great Backyard Bird Count for several years and may take on competitive birding in the future.

At four nursing homes in Connecticut another group of nontraditional birders has emerged: Alzheimer’s and dementia patients. Randy Griffin, a registered nurse, seeking ways to improve the lives of Alzheimer’s and dementia patients, teamed up with Ken Elkins, an education program manager at a  Southbury, Connecticut Audubon center, to bring birding to residents at four nursing homes in the area.  The program they developed, Bird Tales, introduces Alzheimer’s and dementia patients to birds through pictures, models, and recordings, and also suggests ways to make the nursing home grounds more bird-friendly.

All four of the Connecticut nursing homes using the program now practice organic lawn care to attract more birds to their grounds. Additionally, these nursing homes have seen a significant decrease in the amount of medication they are using to calm agitated patients. Elkins visits each nursing home twice a month and spends about a half an hour with each group. He also trains nurses to continue the program in between his visits.

Urbanites represent another unlikely group of birders. Perhaps the best know urban birding spot is Central Park in New York City. The park is a metropolitan migrant trap to which countless birders flock.  Organized bird walks catering to kids and adults alike are offered regularly in Central Park and are also offered in countless other urban areas across the United States including Boston, New Orleans, San Francisco, Minneapolis, Milwaukee and Tucson.

Saving Jaws

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Great white shark (Carcharodon carcharius). Photo courtesy of kqedquest on Flickr.

By Christine Harris

It’s easy to get behind an effort to save pandas or elephants.  These cute, cuddly, charismatic creatures can easily open up the wallets of even the most frugal conservationists, but when was the last time you considered supporting an effort to save a cold-blooded carnivore?  Sharks across the world are experiencing severe population declines as a result of hunting and fishing practices that leave millions of these animals dead annually.

The mainstream media has filled our heads with visions of sharks as evil, man-hungry beasts.  Films like Jaws, Shark Night, and Deep Blue Sea all feature great white sharks on killing sprees.  In actuality, a shark attack on a human is extremely rare.  According to the University of Florida’s Shark Attack Files, worldwide there were an average of only two fatal shark attacks annually between 1999 and 2009.

Large, carnivorous sharks like the great white prefer to feed on marine mammals like seals and sea lions.  Most sharks that “attack” humans have confused them with one of these prey species and will recognize their error when they take a “test bite” of the human and discover that there is little fat when compared to a blubbery seal.

Often surfers, particularly those in the great-white-rich waters off of Australia, are the unfortunate victims of shark attacks.  When one considers the amount of time that surfers spend in the water and the large, dark, shape they take on from below with their boards and wetsuits, it is feasible to imagine how they could be mistaken for a marine mammal.   Though a case of mistaken identity is little consolation to a person who is bitten by a shark, it does dispel the man-hungry myth we have heard so often in popular culture.

Though sharks have traditionally been thought of as a threat to humans, the opposite is more likely to be true.  In one year it is estimated that 79 million sharks are killed by humans.  Of those 79 million, approximately 73 million are killed for use in shark fin soup.  The main conservation issue facing sharks today is the popularity of shark fin soup, particularly in Asia.  As a larger middle class emerges in China, more people are able to afford this delicacy that runs about one hundred dollars a bowl.  The fins are acquired by catching sharks, slicing off the fins and discarding them back into the water where many of them die slowly.

Fortunately, a public billboard and commercial campaign in China featuring basketball star Yao Ming has helped to raise awareness of the environmental impacts of shark fin soup.  Of those who saw the ads, the vast majority said they would stop eating the dish.  Other efforts to protect sharks include those of the Pew Charitable Trusts Environmental Initiatives which have worked with countries around the world to designate 926,645 square miles of ocean as shark sanctuaries which are off limits to shark fishing of any kind.

In China, where shark fin soup is most popular, the government, in June 2013, banned the soup from all official government functions, helping to bring the issue into the national spotlight.  Though the reliability of the statistic is questionable, the Chinese ministry of commerce reported a 70 percent drop in the consumption of shark fins in China in 2012-2013.  As of January 2014, the price of shark fins had fallen 20-30 percent in major Chinese fishing markets, including Hong Kong and Macau, as the demand for fins decreased. Who would have thought that so many people would care about protecting the most feared predators in the ocean?

How likely are you go be attacked by a shark?  Check out this page from the Shark Attack Files.

Saving the Scallop

Atlantic sea scallop (Placopecten magellanicus). (Photo courtesy of NOAA)

Atlantic sea scallop (Placopecten magellanicus). (Photo courtesy of NOAA)

By Christine Harris

It was once believed that the resources of our vast oceans were inexhaustible, yet after centuries of pressure from a fishing industry looking to satisfy increasing demand with the aid of increasingly more advanced fishing technologies, many fish stocks are now seriously depleted.  While so many fisheries are experiencing a downward trend, off the Eastern coast of the United States, from Maine to North Carolina, the Atlantic sea scallop (Placopecten magellanicus) has experienced a remarkable comeback thanks to the collaborative efforts of fishermen, scientists, fishery managers and environmental activists.

By the early 1990s the future of the Atlantic sea scallop fishery looked bleak. It had reached unsustainable levels as a result of years of heavy harvesting.  In fact, sea scallops were in such high demand that it was rumored that some restaurants would fry up circles of dogfish, a small shark, as a substitute because using the real thing was cost prohibitive.

For scallopers fishing off the coast of New England, George’s Bank, a large elevated area of the seafloor stretching from Cape Cod, Massachusetts to Cape Sable Island, Nova Scotia provides rich fishing grounds for Atlantic sea scallops and several other species.  Following the steep decline in sea scallop stocks, managers closed three large areas of George’s Bank in 1994 to any type of fishing gear that would target Atlantic sea scallops and groundfish such as cod and flounder.  Both sea scallop and groundfish fisheries rely heavily on a fishing technique called dredging.  Dredging involves using fishing gear to drag along the bottom of the ocean floor and collect a targeted bottom-dwelling species.  The issue with dredging is that it is difficult to target just one species living on the ocean floor and there is often a large bycatch, or catch of other, unintended species.  Thus fishermen seeking out scallops may end up catching a large number of groundfish, and fishermen seeking out groundfish may end up catching a large number of scallops.

Another rule implemented in 1994 was an increase in the size of the rings in the dredges used for scallop fishing from three inches to four inches in order to allow smaller scallops to escape.  Also at this time a “crop rotation” system was implemented for the Atlantic sea scallop fishery in which certain areas of the Mid and North Atlantic were temporarily closed to fishing to allow the scallops to grow and mature.  The combination of these regulations have allowed the Atlantic sea scallop population to grow ten-fold since 1993 and the fishery has been operating at a sustainable level since 2001.  These developments have helped to make the Atlantic sea scallop fishery the most valuable wild scallop fishery in the world.

The Atlantic sea scallop population has been surveyed annually from North Carolina to Massachusetts since 1979 by scientists working for NOAA’s Northeast Fisheries Science Center. These surveys involve dividing the survey area into zones of varying depth and habitat and towing a dredge to document the marine life and conditions in these zones.  Researchers then analyze their catch to determine the average density of animals.  In recent years a new undersea camera known as HabCam has been used to supplement dredging data.  HabCam was developed by scientists as Woods Hole Oceanographic Institute working with Cape Cod scallop fishermen and can supply information on scallop densities in a less labor-intensive way.

The Atlantic sea scallop fishery also participates in a research set-aside program.  These programs are unique to federal fisheries in the Northeast and involve fishermen setting aside an amount of their catch to be sold in order to fund research.  The research set-aside program for the Atlantic sea scallop fishery has funded industry-based surveys of access areas, research into bycatch reduction and bycatch avoidance, and research on loggerhead sea turtle populations.

Through detailed annual population surveys and the research set-aside program the future of the Atlantic sea scallop fishery looks promising.  Unfortunately much of the seafood we get at restaurants and markets is not part of a sustainable fishery.  To learn more about how to support sustainable fisheries visit seafoodwatch.org.

A Snowy Owl Winter

Snowy Owl (Bubo scandiacus).  Photo by Christine Harris

Snowy Owl (Bubo scandiacus). Photo by Christine Harris

By Christine Harris

Many birders dream of seeing the elusive snowy owl (Bubo scandiacus). So far the winter of 2013 has made that dream a reality for countless avian enthusiasts.  The snowy owl typically inhabits the Arctic and Northern Canada,  yet this winter there have been dozens of reports of sitings from across the contiguous United States, even as far south as Louisville, Kentucky.

According to Marshall Iliff, one of the project coordinators for the Cornell Lab of Ornithology’s Ebird website, when populations of rodents such as lemmings are high, snowy owls experience high breeding success. If those rodent populations crash thereafter, overcrowded owls surge southward in search of food, with younger birds typically moving farther. These snowy owl “incursions” or “invasions” generally occur at least once a decade.  This year’s invasion is taking place primarily in Eastern North America, suggesting that the Eastern Arctic was a productive breeding ground for the birds this past summer, and that they are spreading out to find food.

When seeking suitable habitat and feeding grounds away from their Arctic homeland, snowy owls look for places reminiscent of the tundra: large, open areas with few trees to block their view of rodents scampering on the ground.  Many owls choose open coastal beaches and dunes, while those searching for feeding grounds further inland often settle for airports.  Historically, owls that have chosen to spend time at airports have met with mixed fates.

Birds found at airports are often viewed as a threat to safe aviation.  Remember the flock of geese that led to the “miracle on the Hudson?” In 1960 a plane that departed from Logan Airport in Boston crashed shortly thereafter due to a flock of starlings that were sucked up by the planes engines, killing 62 people.  There is no doubt that the threat to aviation posed by birds at airports is real, and different airports employ different methods for deterring birds from spending time on their runways–including frightening or killing them.  Over the years many snowy owls have been shot at airports; in fact, the only snowy owl to ever disperse to Hawaii was shot at the Honolulu Airport in 2012.

This winter the practice of shooting snowy owls at airports was brought to the attention of the general public when three were shot at New York’s JFK Airport.  Boston’s Logan International Airport has snowy owls visit almost every winter and has had a catch and release program in place for decades.  As of December 11, Norman Smith, director of Mass Audubon’s Blue Hills Trailside Museum, has captured and released 21 snowy owls at Logan Airport and it’s still early in the season.  The most captured in one year to date is 43, but this year could prove to be a record breaker.  Since the beginning of the program over 500 snowy owls have been safely removed from the runways at Logan.

When news broke of the killings at JFK, many asked why New York City did not institute a snowy owl program similar to Boston’s.  Public outrage over the incident led to the New York Port Authority’s decision to work with the New York Department of Environmental Conservation on establishing a catch and release program for New York City airports.  Hopefully New York’s program will meet with the same level of success as that of Boston and future generations of airport-bound snowy owls will be given a second chance.

The Legend of the Woolly Bear

Woolly Bear Caterpillar (Pyrrharctia isabella). Photo by Bob Jenkins

Woolly Bear Caterpillar (Pyrrharctia isabella). Photo by Bob Jenkins

By Christine Harris

Chances are that while enjoying the outdoors on a cool fall day you’ve run across a woolly bear caterpillar.  Topping out at speeds of four feet per minute, these brown and black fuzzy critters are most active in the fall months throughout the contiguous United States as they seek out a cozy, subterranean space to spend the winter.  Woolly bears need to grow and molt six times before they can develop into Isabella tiger moths, which can take several years in colder climates with shorter growing seasons.  Fortunately woolly bears have a unique adaptation to allow them to survive cold winters.  With tissues that contain antifreeze-like compounds called cryoprotectants, woolly bears can survive freezing and thawing throughout the cold winter months.

If you know anything about woolly bears, you’ve likely heard that the width of the brown band on their bodies can serve as a predictor of the severity of the coming winter, with wider bands indicating milder winters.  This well-known piece of folklore was first popularized in 1948 by Dr. C. H. Curran, Curator of Insects at the American Museum of Natural History in New York City.  In that year, Curran and his wife visited Bear Mountain State Park, forty miles north of the city, where they collected a number of woolly bears and measured the length of their brown bands. He found that the brown bands were wide in comparison to the black bands and predicted that the coming winter would be mild.

Curran’s prediction was published in the New York Herald by a personal friend who wrote for the newspaper, and proved to be correct.  Over the next seven years, Curran and his wife traveled annually to Bear Mountain State Park to measure woolly bears.  Through their measurements over those years they found that the bands averaged more than a third of the length of the caterpillars bodies, and the corresponding winters proved to be mild.

 As any well-practiced field biologist knows, the small sample size and limited time period of Curran’s study could not serve as conclusive proof of the woolly bear/winter weather connection, and Curran was under no illusions that it did.  His visits to Bear Mountain with his wife were a much anticipated autumn escape and in later years when his friends joined them, they called themselves The Original Society of the Friends of the Woolly Bear, a group that enjoyed the foliage and caterpillars, but did not take themselves too seriously as scientific researchers.

Isabella Tiger Moth (Pyrrharctia isabella). Photo by Jurvetson (flickr)

Isabella Tiger Moth (Pyrrharctia isabella). Photo by Jurvetson (flickr)

Thirty years after Curran’s last survey, the nature center at Bear Mountain State Park resumed the sampling of woolly bears and continues to do so today.  Though it will take many years and many caterpillars to draw any kind of reasonable conclusions, the park continues the project to maintain an intriguing part of its history and may one day have enough data to determine whether or not a correlation between these caterpillars’ appearance and winter weather actually exists.

 According to Mike Peters, an entomologist at the University of Massachusetts, the brown band on a woolly bear may in fact correlate to the severity of the previous winter rather than the severity of the winter still to come.  There is evidence to suggest that the width of the brown band has to do with the age of the caterpillar.  The earlier in the spring the caterpillars emerge, the sooner they pupate into moths and the sooner the moths lay eggs which will become the next generation of woolly bears.  The earlier the eggs are laid in the spring, the earlier the woolly bears emerge and the more time they have to grow and develop wider bands before they head into hibernation in the fall.  Therefore, instead of predicting a mild winter ahead, a wide, brown band most likely means that the previous winter was mild.

Are they two inch insects, or nature’s oracles? Whether or not they have predictive powers, these ubiquitous, fuzzy little caterpillars, will likely continue to fascinate us for generations to come.

To Feed or Not to Feed the Birds

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By Christine Harris
There are few things I enjoy more than waking up early on a crisp fall morning, making a cup of coffee and peering out the window at the avian activity going on around my many bird feeders.  I have everything a bird could want.  Multiple bird baths, thistle seed, black oil sunflower seed, suet cakes, sugar water; a variable bird-smorgasbord.  My present day fondness for feeding birds was spurred by memories I hold dear of growing up with active bird feeders in my yard and using my dad’s field guides to identify our winged visitors.  Today bird feeders have become an important link to the outside world for many city-dwellers and have been touted as having therapeutic benefits for nursing home residents.  We consider our own enjoyment of the birds, but is this activity really helping them as much as we might believe it to be?  The issue of whether or not to feed wild birds has long been a topic of controversy in ornithological circles.
How could feeding birds be a bad thing, you might ask?  One major concern is that backyard bird feeders are responsible for spreading disease among the birds visiting them.  Whether or not feeders contribute to the spread of avian diseases is a difficult call to make given that most bird species that visit feeders are still associating with other birds in flocks when feeding elsewhere, meaning they may be just as likely to encounter a diseased bird when feeding in another environment.  If you ever do see a bird that appears sick or injured it is best to immediately take down your feeders and wash them thoroughly. According to the Cornell Lab of Ornithology, feeders should be washed with soapy water every two weeks and then soaked in a solution of one part bleach to nine parts water, regardless of whether or not you have seen sick birds in the area.  Hummingbird feeders should be cleaned every time you refill the nectar which should be done every three to five days.
The quality of the seed you are supplying is also important to consider when using outdoor feeders.   Many people hope to save money by buying less expensive bird seed mixes only to discover that birds will bypass their feeders or discard the “filler” in these seeds in favor of a few specific seed types.  Overall black oil sunflower seed is the best bet for attracting a variety species with the same seed type.  This seed is ideal because it is high in fat, relatively small, and has a thin shell that most birds can crack with relative ease.  Any seed that you use should be kept in a sealed container to prevent it from becoming moldy.
What species are coming to your feeders? I am fortunate that I have never seen a house sparrow in my yard, but for many backyard birders this invasive species, or the equally problematic and invasive European starling, will completely dominate their feeders.  Providing a reliable source of food for these species will bring them to your yard in droves and is likely to keep native birds away.  If you find that the majority of the birds visiting your feeders belong to these species it may be best to consider taking them down.
 A frequently voiced concern from backyard bird watchers is that the presence of feeders will prevent birds from leaving when it is time for them to migrate.  Perhaps the most commonly held belief is that hummingbird feeders should be brought in in early fall to prevent the hummingbirds from sticking around and freezing to death.  Though these concerns seem logical, birds evolved their migratory patterns long before humans were feeding them and their migratory instincts are strongly tied to photoperiod (day length). Having seed available to them will not prevent birds from following their instincts.
Though the concerns over the benefit of backyard bird feeders are real, I know that I will continue to enjoy having feeders in my yard for many years to come.  So long as feeders are well-maintained and high quality seed is supplied to native species, bird feeders will always be a good thing in my book.
Photo by Christine Harris