The following commentary was published by The Daily Progress, the daily
newspaper of Charlottesville, Virginia, on September 24, 2024.
 |
You can take a Carolina Chickadee out of the forest, but you can’t take the forest out of this bird. A flawed study unintentionally verified just that. |
ALL TEXT AND PHOTOS © Marlene A. Condon
A serious problem for the
environment nowadays is the scholar- and media-driven promotion of
peer-reviewed scientific studies that do not actually prove what they purport
to establish.
The result is an unknowing
public being led to follow the erroneous dictates of careless scientists,
creating, in the end, more difficulties for our ailing natural world.
A prime example is the
current widespread narrative that “nonnative plants reduce habitat quality for
insectivorous birds”. This quote from a now-famous chickadee study by Drs.
Desirée L. Narango, Douglas W. Tallamy, and Peter P. Marra overgeneralizes
their results that, in fact, only apply to the Carolina Chickadees they
observed and other similarly forest-dependent bird species. In other words, the
scientists have made a statement that is more universal in nature than is
justified by their available evidence.
https://www.pnas.org/content/115/45/11549
This indiscriminate
declaration has served as the keystone argument to
encourage land managers to prioritize growing native-plant
species on properties by first removing so-called invasive, non-native species.
Additionally, it has convinced other scientists, the media, government
officials, environmentalists, and even individuals to disseminate these ideas
far and wide.
However, this entire study is
based upon a flawed premise; its results are therefore not valid; and no
action should be taken based upon the scientists’ recommendations.
For scientific findings to be
considered sound, researchers must follow protocols (an official system of
rules) known as the Scientific Method.
First, they make an
observation: In this case, that some insectivorous-bird populations are
decreasing.
Next, they ask a question:
Could human-dominated landscapes containing an abundance of alien plants that
don’t support many leaf-feeding insects that birds eat be the cause of this
situation?
And third, the scientists
design a study that will enable them to collect data that they can then examine
to determine the answer to their question.
The flaw in the chickadee
study occurred before researchers left the building and got out into the
field. The senior scientists—one of whom was Smithsonian
ornithologist (bird authority) Peter Marra —inexplicably chose the
Carolina Chickadee, a forest bird, as the avian species they would
study in suburbia, which is typically more akin to field habitat.
If people (and their
associated developed areas) did not exist, a chickadee would be found only in
forest because it nests in natural tree cavities. And because it occupies that kind
of niche (the physical space that makes possible survival and reproduction of a
species), it has evolved to feed upon the insects closely associated with the large
native trees that comprise forest.
In other words, the life of a
chickadee is tied forever to large native trees, so any
area without an abundance of these specific plants—as is the case in
much of suburbia—would be regarded as inferior habitat.
By performing their study in sub-optimal
habitat, the three scientists reached a foregone conclusion: A chickadee’s
reproductive efforts will be sub-optimal (fewer healthy chicks) in yards devoid
of numerous large native trees.
A legitimately done study would
have looked at avian species living in suburbia without human-supplied assistance,
such as the feeders and nest boxes that encourage chickadees to try to
reproduce under less-than-desirable conditions. Native birds of field and edge
(where field meets forest) habitats, such as the cardinal, wren, catbird, dove,
jay, mockingbird, and many others, are common and could have been studied quite
easily.
The researchers could have
compared how well these species were able to reproduce in yards with a higher
percentage of nonnative plants versus yards with a lower percentage to see if
it truly made a difference. Of course, as any birdwatching person living in an
urban/suburban area realizes, the birds living and reproducing there do quite
well among the mix of native and nonnative plants.
Urban-/suburban-adapted birds
feed upon a host of insect species, unlike forest-dwelling birds, such as the
chickadee, many kinds of warblers, and other species that are more tied to
leaf-feeding caterpillars and sawfly larvae found in large trees.
It's unfortunate that so many
people have been so fooled by this study. Thanks to Drs. Narango, Tallamy, and
Marra, a great deal of perfectly functioning habitat has been, and will
continue to be, destroyed—often with the application of herbicides that
not only harm wildlife in the area, but can poison the ground and water.
It will take years for
viable habitat to replace it—precious time our wildlife can’t afford—and
there’s absolutely no guarantee, either, that it will consist of native plants.
NATURE ADVICE:
Just because a scientific study by people with “Ph.D.” after their names is peer-reviewed doesn’t mean it cuts the mustard. Always scrutinize what scientists say to be sure their arguments are logically sound.
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