Thursday, September 8, 2022

Red Orioles

Environmental & Science Education, STEM, Biodiversity. Biological Evolution, Wildlife, Nature

Ed Hessler
Two titles, one heading at the top of the first page of a regular column and especially the other heading at the top of the second page of the column about birds by Val Cunningham (StarTribune 8-27-2022),* made me think thought of Eric Carle's book for children, "The Artist Who Painted A Blue Horse." ** This link is to a video where Mrs. F. reads the book and turns the pages. It includes the original painting of a blue horse and a description of the painting by Expressionist Franz Marc.

A reader had sent Val Cunningham some photographs, taken this spring in Pennsylvania, of a red oriole. Cunningham notes that "orioles with unusually red plumage began to be reported in 1993 in Rhode Island and New York state". Humans are implicated (again!).

Cunningham explains "that the color change was likely due to a pigment in the berries of nonnative Asian bush honeysuckles" once promoted by nurseries in the name of habitat improvement have became successful spreaders. They are now described as an invasive species.

Cunningham notes other birds variously affected: "cedar waxwings, white-throated sparrows, yellow-breasted chats, various warblers and northern flickers."  Orioles are not affected physiologically. But the color could have a severe penalty if it becomes widespread through breeding behavior.

Females make their choices based on the "brightness" of the males. It indicates a physically fit, healthy male. A less fit bird could be hidden by the color. Of course it has a scientific term: erythrism.

One unanswered question is whether the color is temporary and lost "after spring time molt."  However, even then, the berries are abundant in the fall and perhaps this will perpetuate the cycle.
* Behind a  subscription paywall. I hope you have access to the full article which includes two males perched together. One in normal colored plumage; the other in red colored plumage.

**The first one read "Diet can produce off-color orioles" and the second one, "Orioles of a different color."

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