Eastern Rhode Island Conservation Committee
Town aims to fool water-fouling geese, one nest at a time
April 21, 2016 | CATHERINE HEWITT Sun Staff Writer
CHARLESTOWN — For the fifth year in a row, town officials and volunteers are working to control the resident Canada goose population by using a humane method known as egg addling or egg oiling.
Geese guano contains nitrogen and phosphorus that increase nitrate and bacteria levels in groundwater and ponds. A Canada goose defecates about 92 times per day, which adds up to 2 pounds of fecal waste.
The resident geese lay an average of six eggs per nest. They don’t migrate. They have a lifespan of up to 25 years and their population increases 10 to 17 percent per year, according to the Eastern Rhode Island Conservation District, a nonprofit, quasi-public organization that promotes the conservation of natural resources.
Since the nesting season began in late March, Town Council President Thomas Gentz, environmental scientist Matt Dowling, and groups of volunteers have been checking nests for eggs on the Ninigret, Quonochontaug and Green Hill ponds.
The addling or oiling process involves testing fertilized eggs for embryo development by placing them in a bucket of water, a step deemed humane by the Humane Society of the United States and People for the Ethical Treatment of Animals.
If the egg sinks, the embryo is not yet viable and is terminated by coating the shell with corn oil, which cuts off the flow of oxygen through the shell. If the egg floats, the embryo is further along in its development and the egg is not oiled.
All eggs are returned to the nest because it is important for the goose to believe they are still developing. If the eggs were removed, the goose would begin laying again.
On Wednesday, Gentz and Dowling checked for nests on Governor’s Island, Hell Island, and Tom Cod Island in Ninigret Pond and oiled 20 unviable eggs.
Dowling kept data on the location of the nests and the number of eggs oiled and unoiled. The eggs were marked with an “x” so that when the nests are checked in a few weeks it will be clear which eggs have been terminated.
Resident Canada geese are covered by the Migratory Bird Treaty Act of 1918. The town files every year for the necessary egg oiling permits from the U.S. Fish and Wildlife Service.
Between 2012 and 2015, the town terminated 526 geese eggs, thus preventing about 75,000 pounds of fecal matter, 222 pounds of nitrogen, and 555 pounds of phosphorus from entering the ponds.
Dowling extrapolated the amount of fecal matter 526 geese would have produced during their lifetimes.
“So far we’ve removed 1.5 million pounds: that’s assuming every goose egg we oiled would have lived 20 years,” he said.