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In the last column, I discussed the positive benefits of bird feeders and noted that no evidence exists to show that birds become dependent on feeders. Growing and selling birdseed is big business with sales of seed and feeders exceeding two billion dollars per year. Over 50 million Americans are involved with some level of bird feeding and observation around their homes. Such broad interest has not always been so.
Anna Botsford Comstock, a professor at Cornell University, started the Nature Study program for children. Kids were encouraged to feed birds and make observations on them. The Nature Study program continued into the 20th century.
The venerable table feeder was in use by the end of the 19th century. Window feeding trays appeared in the early 1900's. Bird feeding was encouraged by the National Audubon Society's magazine, Bird Lore and by two books on attracting birds by Bradford Torrey and Njelte Blanchan. Suet was recommended as a most valuable food. We concur with this advice as fat is more calorie rich than carbohydrates or proteins. Birds store fat to fuel their migrations, their over night shivering and other activities.
We can start in 1854 with Henry David Thoreau. In his classic reflection Walden, he writes of tossing half a bushel of unripe corn just outside his cabin and watching the various animals that were attracted to the corn, including Blue Jays and Black capped Chickadees.
House Sparrows sometime dominated bird feeders. Many people found this introduced species undesirable. Clever inventors produced feeders that allowed agile chickadees to get to the food but not relatively clumsy House Sparrows.
Today, we'll look at the history of bird feeding in North America. This topic has long been a research interest of mine. This column benefits greatly from information in Feeding Wild Birds in America by Paul Baicich and others.
[Originally published on December 13, 2015]
We return to research done by Brittingham and Temple in Wisconsin. Having shown that bird feeding increases winter survival of Black capped Chickadees, these ornithologists set up an experiment to test for feeder dependence. In one area, chickadees had been given sunflower seeds continuously for several years. In the second area, no bird feeders were ever present.
Waldo Lee McAtee, a federal biologist, advocated using coconuts or tin cans with small holes as feeders. Such feeders minimize the loss of food. The holes could be made small to allow chickadees access but not larger birds that tended to outcompete chickadees at a feeding table.
If the population given sunflower seeds in previous years had a lower survivorship than the population with no bird feeders, one could claim that the birds in the first area had become dependent on the sunflower seeds. But there was no difference in survivorship for the two populations. The previously fed chickadees did as well in the following year feeding on natural food, as the unfed chickadees did that never experienced the bounty of bird feeders.
Margaret Brittingham and Stan Temple examined the impact of bird feeding on the winter survivorship of Black capped Chickadees in Wisconsin. They banded over 500 chickadees. Some populations were given access to unlimited sunflower seeds and some populations had to depend on natural food. Over the course of three winters, Brittingham and Temple found that winter survivorship of banded birds with access to supplemental food was 67% compared to 37% for birds without sunflower seed handouts. That's a pretty striking result.
Bird feeding is a two way street. We feed the birds to help them survive but also feed to lure the birds closer to us so that we may enjoy their beauty and behavior.
These results have been corroborated in similar studies done in Pennsylvania and Ontario.
We fast forward to 1898 when Florence Merriam Bailey began teaching bird classes to teachers in the District of Columbia. Bailey had recently graduated from Smith College and had been actively involved in battling the harvest of egrets. These birds were being slaughtered in large numbers because their breeding plumes had become fashionable in women's hats.
By 1910, more sophisticated bird feeders began to appear. Hans Berlepsch, a German, had begun to design bird feeders that minimized waste. His bird bell (a silo like contraption in which seeds fell onto a tray) was one of the most popular.
A number of readers have contacted me recently with a concern about bird feeding. Holiday travel means that our bird feeders may be depleted while we are away, depriving birds of our handouts. Readers are asking if we are doing harm to birds by providing and then removing food.
Commercial bird feeders became widely available in the 1920's and bird feeding continued to increase in popularity. To be sure, World War I and the Great Depression forced cutbacks in bird feeding but bird feeders were a common sight in 1940. We'll continue in the next column.
Tom Grubb and his students used this technique to examine the impact of bird feeding. They captured Downy Woodpeckers, White breasted Nuthatches, Carolina Chickadees and Tufted Titmice in the winter in Ohio. The researchers plucked one of the tail feathers of each bird. The birds quickly started replacing that missing feather.
This query requires us to answer two questions. First, do birds Buy Women Canada Goose Trillium Parka Pink Australia benefit from bird feeding? Second, do birds become dependent on bird feeders?
The answer to this first question is yes. One line of evidence comes from a technique called ptilochronology, a daunting word that refers to the rate of feather growth. Did you know that you can see daily growth bars on a feather? Each contour feather a bird produces has a record of how quickly it was formed.
At the same time, Elizabeth Davenport in Vermont fed the birds a diversity of seeds as well as cornbread. She kept careful records, documenting over 20 bird species at her feeders.
The researchers found that the greatest risk to the control (unfed) birds was in the coldest months with more than five days with subzero temperatures. Chickadees with supplemental food were also heavier than the control birds.
Similar studies have not been done for other North American species that frequent feeders but I expect that results would be similar. Depending on a single source of food is risky for any winter bird. Winter songbirds commonly range over areas of 10 to 25 acres. Much of this area is regularly patrolled and food is taken from a number of different parts of their winter area.
Half of the birds had access to bird feeders and the remainder were found in areas where only natural food was available. After a month or so, the birds were recaptured and their regrown tail feather was examined. The birds with access to supplemental food regrew their tail feathers at a faster rate; the daily growth bars were longer in these well fed birds. So, bird feeding increases the nutritional status of birds.
Bailey showed that nailing a few bones and suet to a tree attracted a diversity of birds. She recommended grains and table crumbs as well.
The first suet feeders appeared at about this time. Rather than simply tying or nailing suet to a tree, people began to make suet boxes from wood or metal. Some people mixed seeds in with the suet.
Birds therefore benefit from the food we provide for them. But is there a risk that birds become dependent on our handouts? The answer to that question is no to the best of our knowledge.
2016 January 04 Maine Birds