Seeking to solve mystery songbird illness

Certain natural chemical properties found in the tree of heaven could be toxic to animals such as songbirds if consumed.

The most likely suspect in the “case of the mysterious songbird illness” seems to be the one flying furthest under the radar.

Ninety-eight percent of all songbirds feed their babies bugs. In nearly all reports, fledgling or young songbirds appear to be the population most susceptible. Spotted lantern fly babies hatch in the spring and bugs are plentiful, especially in Pennsylvania.

The spotted lantern fly’s food of choice is the Ailanthus altissima, commonly known as tree of heaven. Both are invasive species, both are problematic in different ways. Efforts are underway and ongoing to rid the country of both in a rather aggressive manner.

It has been proposed that certain natural chemical properties found in the tree of heaven could be toxic to animals such as songbirds if consumed. After the spotted lantern fly feeds on the tree, it excretes a sugary mildew substance which is appealing to certain insects such as ants and wasps. It is no secret that songbirds eat the spotted lantern fly — even pictures posted through Penn State Extension demonstrate clear evidence of a songbird with a lantern fly in its beak. It’s been theorized that songbirds don’t feed directly from the sugary substance excreted by lantern fly because the substance (which turns to toxic mold fairly quickly) is quite bitter to the taste. But there problems with this theory.

One problem is that research suggests that some songbirds might have “lost their sense for sweetness” through the evolutionary process. Evolutionary biologist Maude Baldwin believes, “The only known exception are the hummingbirds, who repurposed their umami taste receptor to recognize carbohydrates.” If Baldwin’s theory is correct, then the hatching of stage 1 spotted lantern fly in early spring instantly becomes the most abundant food source for songbirds, particularly in Pennsylvania where the lantern fly has reached pandemic status, and especially for hungry fledglings.

On April 19, 2021, Penn State’s College of Agricultural Sciences published the brief article, “Researchers devise creative ways to defeat a destructive pest.” The following news was revealed in the article: “Suet containing ground-up spotted lantern fly adults that have fed on tree of heaven, which contains compounds that may create a bitter taste to birds, or grapevines, which are not bitter, will be placed side by side in feeders attached to trees. Video cameras will record birds that visit the feeders and the suet cake they prefer.

“The investigation also enlisted the help of bird watchers, who are positing reports, videos and photos of birds they see feeding on spotted lantern flies. One month into the project, (they) had already received more than 800 reports.”

Meanwhile in a quarantined laboratory, “Researchers will analyze the insects for chemical compounds present during each life stage while examining tree of heaven sap as the potential source of these chemicals.”

The spotted lantern fly is a great hitchhiker and the songbirds are disoriented. That’s how you discover an infestation of spotted lantern fly in Indiana on July 23, 2021.

It’s an explanation that makes sense, and maybe the only one.