|MadSci Network: Zoology|
With the help of an excellent reference librarian, I have found two original research publications that appear to address this question. They are: * Alderisio, K. A., and DeLuca, N. 1999. Seasonal enumeration of fecal coliform bacteria from the feces of ring-billed gulls (Larus delawarensis) and Canada geese (Branta canadensis). Appl. Environ. Microbiol. (65):5628-5630. * Bedard, J., and Gauthier, G. 1986. Assessment of faecal output in geese. J. Appl. Ecol. 23 (1):77-90. The 1986 report was about how often geese defecate and was done by observing greater snow geese in Canada (i.e., not Canada geese as such). While feeding, the geese averaged from 5.23 to 18.79 defecations per hour, depending on the feeding site and the year of observation. Unfortunately, the authors do not indicate how many hours per day the geese were likely to feed, nor whether they also defecated when not feeding. The 1999 report was about how much the average Canada goose fecal deposit weighed and the level of fecal coliform bacteria it contained. Average weights ranged from 5.85 to 9.98 grams, depending on the season. Fecal coliform bacteria contents (probably mostly Escherichia coli) averaged from 4,500 to 24,200,000 colony-forming units per gram of feces, depending on the season and year of observation. The bacterial levels were consistently lower than those for the seagulls that were observed in the same study, supposedly because the geese are largely vegetarian grazers. If we assume the a goose's daily fecal output is the equivalent of 6 hours of grazing, the 24-hour total might be as much as 126 to 451 defecations, with weights ranging from 5.85 to 9.98 grams. The smallest number times the smallest weight gives 737 grams (~1.6 pounds); the largest number times the largest weight gives 4501 grams (~9.9 pounds). Using a mid-range value for each (288 × 7.9) gives 2276 grams (~5.0 pounds). For a mid-range value of 300,000 colony-forming units per gram, this would be about 683 million colony-forming units per day, which may or may not be a leading source, depending on what else is going into the water. At least you can see that the estimate of 46 pounds of fecal output per day is about 10 times too high.
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