Blog #359 Nesting in a Polluted World 2021

Stuffed toy being brought to Osprey nest, courtesy of njwildlife. 

Ospreys have a long history as a vital indicator species: the health of their populations is directly linked to their surrounding environment. When we poisoned the land with persistent pesticides, the ospreys told us. When we overfished menhaden, the primary prey of coastal ospreys, the ospreys told us. When we use and discard plastics carelessly, the ospreys tell us. 

Birds worldwide began incorporating anthropogenic materials (hereafter referred to as 'debris') into their nests when the first use of natural fibers such as wool, flax, and cotton appeared by humans millennia ago. Since the development of plastic fibers in the

1940s, they have been strewn across the landscape, making their way into bird nests around the globe. Is the sight of garbage in nests just an annoying sign of the times or is there a concern about the long-term consequences of these novel nesting materials on osprey behavior, natural history, and long-term health? 

Coot on top of nest made of garbage, courtesy of Pinterest. 

Birds worldwide have a long history of incorporating anthropogenic materials (hereafter debris) into their nests since the first use of natural fibers such as wool, flax, and cotton by humans millennia ago. Since its development in the 1940s, the ubiquitous use of plastic fibers by society has left synthetic debris strewn across the landscape, making its way into bird nests around the globe. Is the sight of garbage in nests just an annoying sign of the times or is there a concern about the long-term consequences of these novel nesting materials on bird behavior, their natural history, and their long-term health? 

First let’s look at how widespread plastics are in bird nests. Plastic debris in nest common to both marine and terrestrial birds species. A global study of nearly 10,800 nests representing 24 species found plastic debris in over 30% of them. The incorporation of such debris was strongly correlated with the increased human impact on the proximate environment. 

An Australian study examined 893 nests made by 224 species sourced by museums from 1832 to 2018. They found debris increased from approximately 4% of the nest materials in 1832 to 30% of the contents in 2018. This change was driven by the development of plastics in the 1940s, which led to a massive global increase in synthetic debris. A small study in Costa Rica found 53% of the nests examined contained debris, primarily wool, thread, string, and plastic filaments. 

Why do the birds incorporate plastic and such synthetic materials in their nest? That’s the ten thousand dollar question. It is notorious difficult to discern advantages and

Swan nests made of debris, courtesy of Pinterest. 

whether they are there by intent. That the process has persisted through generations, however, suggests that there are indeed advantages. The birds might enjoy decorations. Strongly woven fibers may offer structural support to the nest. Some may have thermal advantages by either providing shade, insulating the nest, and or serving as wind breaks. Soft materials like artificial Easter basket grass or shredded plastic bags are used to line the inner nests, possibly providing insulation or cushioning eggs. One red-tail hawk was seen covering its eggs with a piece of plastic sheeting, possibly to keep them warm. Finches show a preference for using food wrappers instead of readily available plant materials. Blue Grosbeak nests commonly contain shreds of old newspaper, plastic bags, string, paper, cardboard, and other items more unusual items such as sleeping bag insulation. Thornbird nests in South America are comprised of up to 90% plastic—mostly discarded plastic wrappers and packaging materials. 

Sparrow nest with cigarette butts, courtesy of Are.na. 

Perhaps the most interesting thesis is that some debris reduces harmful ectoparasite loads in the nests, a function normally achieved using select green plants. Some species such as house sparrows and house finches have learned to recognize used cigarettes (clean filters do not work), rip off the filter, and unweave the cotton fibers into the nest. The nicotine in these fibers repels mites while the fibers insulate the nest. However, there are many toxic substances in addition to nicotine in the fibers, such as

ethylphenol, heavy metals like titanium dioxide, propylene glycol, diverse insecticides, and even cyanide may exact a cost. The eggs, chicks, and adult females, who spend significant time at the nest, absorb the toxic substances through their skins upon contact with the nest materials. Test results indicate that chick erythrocytes show genotoxic damage proportional to the cigarette fibers lining their nests. It is also suspected that these volatiles are also contracted through inhalation. Genotoxic damage occurs when these agents break DNA chains during mitosis, a process that can lead to mutagenicity and eventually to carcinogenic processes. The long-term effects of cigarette butts chemistry on the life cycles of these and similar bird species remains unknown. 

The other silent killers in the nest are baling twine, monofilament fishing line, plastic string, mylar balloons, netting, sixpack rings, and plastic bags. These materials can strangle the young and the adults whose limbs become entangled. Plastic particles, 

Dead Osprey entangled in fishing line, courtesy of npr. 

looking like natural food bits, are also ingested causing starvation. This isn’t just a problem of Osprey nests, although they are perhaps the most prolific garbage scavengers. Birds and mammals of many persuasions get fatally tangled in hazardous plastic. The plastic use of American crows living in urban and agricultural areas of California’s Sacramento Valley was measured. Of the 106 crow’s nests studied, 85.2% contained debris with 11 of 195 nestlings (5.6%) fatally entangled in fishing line and other string-like materials their nests. 

Next time you pass a messy Osprey nest on the road with black plastic garbage bags billowing in the breeze, note that Ospreys are not the messy housekeepers, we are. They are responding to global pollution and mirroring the condition of the landscape.

The sight of a garbage-strewn Osprey nest should stir you to action! Cut your personal plastic consumption and work to get plastics out of our water, air, soil, food, and bodies. 

Eyes tothe sky! 

Candace 

Candace E. Cornell 

Friends of Salt Point 

Lansing, NY 

Friends of Salt Point Natural Area 

Cayuga Lake Osprey Network 

NY cec222@gmail.com