Making Use of the Most Common Bird With Citizen Science
Today’s citizen science blog post is brought you by Mariah Patton, Aubrey Wiggins, and Dr. Caren Cooper. Mariah is the project manager for Sparrow Swap, Aubrey is a dedicated Sparrow Swap volunteer and citizen scientist, and Dr. Caren Cooper heads the Sparrow Swap project. Thanks everyone!
There are certain species commonly associated with humans, including domesticated species like cats, dogs, and farm animals. One wild species that is found wherever people are found is Passer domesticus, the House Sparrow.
The House Sparrow is one of the most common birds in the world. In some portions of its native Old World range, its decline is of concern, but it is an abundant invasive pest in many areas of the world, including the United States. As we’ve learned with dandelions and kudzu, once an invasive species gets a foothold, it is virtually impossible to get rid of it.
However, it is possible to minimize damage it may cause. House Sparrows are NOT a threat to endangered species, NOT a threat to agriculture, NOT a general threat. But they DO pose harm to bluebirds by taking over their nesting sites and sometimes killing them. Of the thousands of bluebird enthusiasts across the US, many do battle with House Sparrows. To find the most effective strategies to minimize House Sparrow damage to bluebirds, Dr. Caren Cooper’s research team at the Museum’s Biodiversity Research Lab collaborates with bluebirders across the country in a citizen science project called Sparrow Swap.
Sparrow Swap volunteers, those who monitor nestboxes they’ve installed for cavity-dependent bluebirds, view the more generalist House Sparrow and their ability to outcompete for nesting space as problematic. Because House Sparrows are not protected in the US under the federal Migratory Bird Treaty Act, many bluebird nestbox monitors employ a range of actions to keep this sparrow’s population in check while reducing fierce nesting competition for the native, less abundant, and more favorable bluebird. These actions include using passive scare tactics such as a monofilament wire device commonly known as a “Sparrow Spooker,” to more aggressive tactics such as trapping and euthanization. So far, however, little research has been done to shed light on what works and what may have unintended consequences. Through long-term and large-scale data collection, the Sparrow Swap team hopes to get a clearer picture of these issues to share with their citizen scientists and nestbox monitoring communities across the United States.
Sparrow Swap citizen scientists are asked to manage a House Sparrow-dominated nestbox by either removing the eggs and nest from the box or swapping the eggs with hand-painted replicas sent from the Museum. Whichever of these commonly practiced management strategies they choose, it is important for Sparrow Swap citizen scientists to record observations for at least 3 visits and document any additional nesting attempts. This will allow us to determine which management strategy works best at deterring House Sparrows from using bluebird nestboxes.
Observations this year have led to interesting preliminary results! These data show that 49% (N=35) of removals (eggs and nest) resulted in a renesting attempt by the second visit seven days later. Furthermore, 60% of these removals also resulted in new eggs and/or chicks by the second visit. While about half of removals resulted in new nesting attempts, over three-quarters of nests (N=100) with egg replicas successfully tricked parents into investing wasted energy on replicas, and new eggs and/or chicks appeared only 13% of the time. While more data are needed to confidently tease apart outcomes of swapping eggs vs. removing eggs, these preliminary data suggest further trials are warranted to understand the effectiveness of swapping egg replicas.
In addition to assessing the effectiveness of management tactics, the Sparrow Swap team is investigating whether House Sparrow eggs are useful for monitoring and mapping environmental pollutants. They are also interested in whether there is any connection between possible pollutants and eggshell characteristics such as porosity, eggshell thickness, and color/pattern variation. The Sparrow Swap team has already curated over 479 eggs and stored contents for future lab analysis once more funding is secured. If pollutants are found in the eggs of this species, a species that is only found in association with people, House Sparrow eggs could act as a bioindicator of pollution exposure in other animals and humans.
So, why should bluebird enthusiasts toss out a perfectly good House Sparrow egg from a nestbox when it could be used for science? Not only do these unwanted House Sparrow eggs serve as potential bioindicators, but they will be donated as specimens to the Museum’s collections so they will be available for further research for years and years to come.