by Carl Strang
[Note: this post first appeared as a Nature Note in the Observe Your Preserve website]. Back on May 11 I watched a female Baltimore oriole as she attempted to collect some monofilament fishing line tangled in a shrub at the edge of May’s Lake in Mayslake Forest Preserve. After at least 5 minutes of effort she gave up and flew away. A couple weeks later, a member of a group I was guiding spotted an oriole flying to a nest in a large oak tree near that point on the lakeshore. Early last week I found that nest on the ground beneath the tree, apparently detached by one of our recent wind storms.
It soon became clear that the nest was composed largely of fishing line and other plastic fibers like those woven to form blue tarps. Perhaps inevitably, some of the line had a fish hook tied to the end.
This is a rare instance when leaving litter, in particular fishing line, had a harmless or perhaps helpful impact on the local wildlife. Most of the time such material is dangerous, posing an entanglement hazard that could result in death or serious injury to wild animals. That line is designed not to break easily. In time it may physically erode, but it will not decompose and it potentially puts wildlife at risk for years. The importance of picking up your litter cannot be overemphasized.
To this point the story was worth posting about, and I did so in the Nature Note at Observe Your Preserve last week. It turned out that there was an additional chapter to come, however. Later in the week, as I walked along the top of the savanna ridge not far from where I found that nest, I looked up and noticed that last year’s Baltimore oriole nest still is attached and largely intact.
It proves to have much fishing line and at least one strand of a similar blue plastic weave. A comparison to the photo I made last December confirms that it is the same nest, and that there has been very little change, except that the supporting twigs have grown.
This underlines the persistence of these plastic materials, and it raises other questions. Were the two nests woven by the same female, one with a preference for these synthetic fibers? The nests were, after all, built only a few trees apart from one another. Alternatively, would any oriole take advantage of the availability of such fibers?