Osprey Entanglement (guest blog post)

Communication is an essential part of science. The Canadian Field-Naturalist wants to encourage science communication among Canada's early-career naturalists. Below is a story about a research article in issue 128(2), authored by Lauren Banks, a first year Environmental Science graduate student at Trent University. Lauren was not involved in this study.

Living in harmony

Good science is predicated on attention to detail, as one of the Myth Busters from the show of the same name said, “the only difference between science and screwing around is writing it down”. Great science, however, involves intricate planning based on clear objectives. The researchers and citizen scientists involved with this study skillfully combined both of these wisdoms to create a clear, unbiased evaluation of the effects of polypropylene baling twine and its use and implications for nest building by Osprey and their nestlings.

Figure 1- A pair of Osprey building a nest. Photo by Jerry Kirkhart, courtesy of Wikipedia.

Like many ecological questions, this study was inspired by observations about nature. In this case, researchers noticed discarded baling twine (used to wrap hay bales) en route to various Osprey nesting sites they were surveying. Osprey often incorporate people’s discarded items, such as string or baling twine, as nesting material. Though these items can provide more access to materials for nest construction, some of these materials may entangle nestlings. The researchers wanted to investigate to what extent Osprey used these items, and whether there was an increased risk of entanglement if baling twine was used to construct a nest.

The setup

The study area was in Yellowstone River floodplain, an area that encompasses a variety of anthropogenic land uses. During 2012 and 2013, both the researchers and citizen scientists monitored Osprey nests within the study area. Based on 71 nests, buffer zones around each nest were created to evaluate potential roadsides for baling twine collection. As a proxy for rural to urban land-use, the researchers used GIS to map road density, based on total length of roads, in each buffer zone.

Baling twine more abundant in rural areas

Of the 65 nests that were initially selected for baling twine assessment, 38 met the criteria for this study. Interestingly, all 65 Osprey nest sites were constructed on human-made structures, such as power poles, nest platforms, and bridges.

Surveys of the nests themselves revealed that there were almost twice as many nests constructed with twine in rural landscapes than in urban areas. However, Osprey used a similar amount of twine regardless of twine availability in areas surrounding their nest.  This can partially be attributed to Osprey behavior; Osprey use objects that are noticeable or unnatural to show other Osprey that the territory near the nest is taken by an Osprey of high social status and nest building prowess. Perhaps twine might not be the most desirable material to use for this display of dominance.

A new approach

Being one of very few studies to evaluate baling twine and impacts on nest building and nestlings, the researchers have delved into unchartered territory and are effectively creating a map for future assessment. In agricultural areas, hay pastures and feedlots can produce lots of baling twine, some 115m of twine per bail (Houston and Scott 2006). With sometimes haphazard disposal, it’s probable that baling twine can be transported from unsecured piles to roadsides and eventually to Osprey nests. Beyond simply finding twine in roadsides and nests, there are tangible impacts for nestlings. Twine is slow to degrade, so if a young nestling becomes tangled in baling twine, it’s unlikely the Osprey parent would be able to disentangle their young (without the help of humans). Use of baling twine has real consequences for Osprey, whether it is on a statistical or real-time level. In addition to developing a meticulous sampling protocol, the researchers also engaged with another crucial component, people.

A key aspect of this study was partnership with citizen scientists, which allowed for more extensive nest observation, and with the non-profit Yellowstone Valley Audubon Society, which aided in developing educational materials based on the results of this study. Cultivating solutions, such as short-term clean up efforts and educating farmers and ranchers about the issues associated with improperly disposing of baling twine. Long-term alternatives like netting or wraps, materials that Osprey don’t appear to use, can affect fundamental change and help protect species with which we share the planet.

Article Citation: Seacor, R., Ostovar, K., Restani, M. 2014. Distribution and abundance of baling twine in the landscape near Osprey (Pandion haliaetus) nests: Implications for nestling entanglement. Canadian Field-Naturalist 128: 173–178. http://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/1582

The corresponding author for the study, Dr. Marco Restani of St. Cloud State University, welcomes questions about the research.

Reference cited: Houston, C. S., and F. Scott. 2006. Entanglement threatens Ospreys at Saskatchewan nests. Journal of Raptor Research 40: 226–228.

Lauren Banks is an Environmental Science Master's student at Trent University in Peterborough. She studies freshwater plants, but curiosity has lead her to adventures with bees, martens, and farming.