The Dutch authorities insist it must be done, too. They pay Mr. Den Hertog to keep a ballooning geese population from devouring the grass of cow pastures and flying into planes taking off from Amsterdam’s Schiphol Airport, a major hub in Europe. He is the unpleasant answer to what has become a problem on a grand scale for the Netherlands.

Geese populations here have skyrocketed, buoyed by a 1999 ban on hunting them; farmers’ increasing use of nitrogen-rich fertilizer, which geese apparently love; and the expansion of protected nature areas. That combination, plus an abundance of rivers and canals, has made the country a “goose El Dorado,” said Julia Stahl, head of research at Sovon, a group that monitors wild bird populations in the Netherlands.

Birds that used to return to the Russian Arctic and elsewhere in the summer are increasingly staying put. Dr. Stahl estimates that the graylag goose, which seemed to be dying out in the Netherlands in the 1970s, now accounts for three-quarters of the goose population, which can reach 800,000 in the summer and double that in the winter.

As long as animal rights activists do not interrupt the gassings, Mr. Den Hertog said, passengers flying to and from Schiphol Airport do not need to worry whether their pilots have the same skills and sang-froid as Chesley B. Sullenberger III, the US Airways captain who managed to land in the Hudson River in 2009 after geese knocked out his plane’s engines.