Analyzing House Sparrow Eggs for Environmental Contaminants
If you’ve ever looked through our Sparrow Swap website, we mention that we hope for our House Sparrow eggs to be analyzed for contaminants as part of research to determine if House Sparrow eggs are useful indicators of human exposure to environmental contaminants. We are currently looking at heavy metals in the eggshells, but hope to also look at other persistent environmental contaminants in the egg contents
Before we decide on what contaminants to test the eggs for we have to consider the feasibility of testing eggs for contaminants, explore why we should be testing for certain contaminants, and understand what research has already been done. To do so we look at the work of other scientists studying contaminant in bird eggs including Dr. Seth Newsome at the University of Wyoming and Dr. Nellie Tsipoura at the New Jersey Meadowlands Commission.
Flame retardants and Peregrine Falcons
One contaminant of emerging concern among wildlife, including birds, are flame retardants. Flame retardants are primarily composed of polybrominated diphenyl ethers (PBDEs for short). These fire retardants are in many items that can be found in virtually every household. PBDEs are added to carpets, furniture, electronics, and even buildings and cars in order to reduce the flammability of these products. PBDEs have recently become a contaminant of interest due to its ubiquitous nature, but not much is known of the effects of PBDEs on organisms and the environment. In 2010, Newsome et al. published a study in Environmental Science & Technology that investigated the presence of flame retardants in peregrine falcon eggs. These researchers found that high levels of PBDEs were present in the eggs of peregrine falcons that were collected from California cities. They concluded that the PBDE concentrations in urban peregrine falcon eggs were significantly higher than the eggs from rural areas. As a result, this study was able to identify a connection between diets composed of food produced by humans and high PBDE concentrations. The Sparrow Swap Team is also planning to use the membrane of the eggshell to determine the diet of the female. This may tell us if House Sparrow diets are similar to humans which could mean that we may be exposed to similar contaminants found in the House Sparrow eggs.
This study is very reminiscent of a previous study that was popularized by Rachel Carson in her book Silent Spring. Alarming levels of dichlorodiphenyltrichloroethane (DDT) were found present in peregrine falcon eggs. Eventually, scientists were able to connect the widespread use of DDT to the large population declines in peregrine falcons, as well as other raptor populations. Eggshell thinning, which caused reproductive success to greatly decline, was occurring due to DDT accumulating in these organisms via dietary pathways. Eerily similar circumstances are occurring right now with peregrine falcons, along with other wildlife. We are also measuring eggshell thickness, particularly how thickness may be associated with heavy metal concentrations.
Heavy Metals and Canada Geese
Heavy metals, such as lead, mercury, cadmium, and more, are also of concern. We are testing the House Sparrow eggs that our Citizen Scientists have collected for lead, cadmium, arsenic, copper, and selenium. These contaminants are of concern due to their ability to accumulate in sediments and in organisms. These heavy metals are particularly known for their ability to bioaccumulate in organisms, which occurs when the intake rate of a substance is greater than the excretion rate by the organism. As a result, contaminant concentrations within an organism tend to be higher than the concentrations in the environment around it.
In a previous study conducted by Dr. Nellie Tsipoura at the NJ Meadowlands Commission, Canada Geese living within the New Jersey Meadowlands in 2010, known for its heavy pollution from effluent and runoff from nearby industries and traffic, were tested for Lead, Cadmium, Arsenic, Copper, and Selenium. In this study, researchers collected the eggs, along with feathers, muscle, and liver tissue of the Canada Geese. The eggs collected from the Meadowlands were found to have higher lead levels when compared to Canada geese eggs collected from other areas as well as eggs from other bird species living within the same habitat. These higher lead concentrations are concerning because it is possible that the concentrations will be passed on to predators after they consume the eggs. The researchers noted that this opens the possibility for many levels of the food chain to be contaminated, even humans. The presence of the contaminants represents a possible threat to humans, as well as other wildlife in the area that may be exposed to these heavy metals, either through direct exposure or through dietary pathways.
Our Next Steps
Similar to these studies, we are analyzing the House Sparrow eggs that we have received for environmental contaminants. We are taking the first steps to see if House Sparrow eggs can be used as an indicator for contamination in wildlife and potentially in humans.
Want to learn more, here are the original articles:
PBDE Study: https://pubs.acs.org/doi/10.1021/es100658e
Heavy Metal Study: https://www-sciencedirect-com.prox.lib.ncsu.edu/science/article/pii/S0013935111001423
This post was written by Skyler Price. To learn more about Skyler and the rest of the Sparrow Swap Team, check out our Team Page.