In Defense of Nature

                             

Chickadee Chicanery

 

A Carolina Chickadee grasps a Tulip Poplar (Liriodendron tulipifera) seed it found in the author’s yard. Seeds are an essential component of this bird’s fall and winter diet.

ALL TEXT AND PHOTOS © Marlene A. Condon

 

Prefatory comments: You’ve probably heard of Doug Tallamy and his famous chickadee study that claims its “results demonstrate that nonnative plants reduce habitat quality for insectivorous birds”, and thus “private landowners should prioritize native plant species” on their properties.

 

These overgeneralized statements are: (1) fallacious, as they are based upon the mistaken belief that a Carolina Chickadee is urban-adapted, as if it can nest successfully in virtually any yard containing a bird house; (2) wrong, in that they are only applicable to the Carolina Chickadee and similarly forest-dependent species; and (3) misleading, as the authors left out the word “woody”, leading the reader to believe they include herbaceous plants, which they don’t.

 

Unfortunately, people have been so misled by this study that much perfectly functioning habitat has been destroyed, often with the assistance of herbicides that not only bring harm to wildlife in the area, but can also accumulate in the environment.

 

Something is amiss in the realm of ecological sciences when a paper is peer-reviewed and published despite being deeply flawed in its execution, and its results so overgeneralized as to deliver several faulty conclusions. Such is the case with “Nonnative plants reduce population growth of an insectivorous bird”, published in 2018 by Desiree Narango, Douglas Tallamy, and Peter Marra.

 

https://www.pnas.org/content/115/45/11549

 

The scientists state they performed this research to rectify that “no study has examined the impact of nonnative plants [in urban areas] on subsequent population responses of vertebrate consumers”. They chose as their study subject the Carolina Chickadee—a forest bird that too many people mistakenly believe to be generally “urban-adapted”. Surprisingly, this group included ornithologist Peter Marra, director of the Smithsonian Migratory Bird Center, whom one would expect to realize that the Carolina Chickadee can nest successfully in an urban area only if the area is well wooded.

 

Chickadees are as tied to large native trees (the definition of forest) as fish are to water because these trees provide both the natural cavities for nesting and the multitude of leaf-eating arthropods to feed a chickadee family. In other words, for a chickadee population to be sustained in urban areas, there must exist (1) natural forest nearby (parks/natural areas or unbuildable areas between homes where trees remain) or (2) virtual forest (from the perspective of a bird flying above the canopy) because a profusion of mature trees surrounds homes.

 

So yes, you may entice a chickadee into your yard with an artificial cavity (a bird house), but you better have nearby forest to fully support it. Narango, et al., overlooked this ecological niche of the Carolina Chickadee, which automatically would have told them this species couldn’t possibly do well in a novel environment of mostly nonnative woody plants (their image of most urban areas) that are “poor at supporting [caterpillar and caterpillar-like] insects that are critical food resources”—a fact they pointed out in the introduction to their paper.

 

Truth be told, calling a forest-dependent chickadee urban-adapted is comparable to, for example, doing the same for the Purple Coneflower (Echinacea purpurea) of prairies and meadows simply because it’s able to flower and make seeds in many yards. Both the chickadee and the coneflower will only thrive, however, if their ecological requirements are met—large native trees to sustain the bird and at least six to eight hours of sunlight a day for the plant. This information is well known, so performing a study to prove its easy-to-understand veracity is a waste of time, effort, and most importantly, grant money.

 

Therefore, these three scientists had no justifiable reason to expect a chickadee to successfully reproduce in “fields” (i.e., yards). To study the effects of nonnative woody plants upon birds in urban areas, which the investigators were purportedly trying to do, you must study legitimately urban-adapted native birds (i.e., those species that move in of their own accord to landscapes not intentionally created for them—for example, an Eastern Phoebe that chooses to nest on a gutter downspout). Thus, the Narango, et al., paper should have been rejected for publication first and foremost because the scientists studied a bird of the forest in an urban setting, which should have axiomatically told the reviewers (as well as the researchers) that their results would be erroneous—as they certainly are.

 

The authors write that “[their] study suggests that nonnative plants do not provide enough arthropod prey during reproduction to sustain bird populations”, but if this statement were accurate, there’d be no Brown Thrashers, Gray Catbirds, Northern Cardinals, or Northern Mockingbirds spending the breeding season in urban/suburban yards to reproduce. The fact is that genuinely urban-adapted birds do find enough insects to feed their nestlings, reproducing quite well in yards with many alien woody-plant species because other kinds of birds are not as dependent as chickadee chicks upon the caterpillars and sawfly larvae that only native trees can provide in abundance.

 

My own experience over the past 34 years (documented in writing and photos that provided the basis for my book) clearly demonstrates that a mix of native and nonnative plants of all kinds constitutes excellent habitat for a vast array of organisms, including the Carolina Chickadee because forest is nearby.

 

Garden/news writers and native-plant/conservation groups have glommed on to these study results, but these folks have been seriously deluded.

 

NATURE ADVICE:

Unless your yard has forest nearby, you probably shouldn’t try to coax chickadees into reproducing there by putting out a bird box—the only legitimate recommendation to be derived from the Narango, Tallamy, and Marra study, which (although they didn’t intend it) conclusively proves the Carolina Chickadee is, indeed, a forest-dependent species.