U.S. Department of Agriculture: Animal and Plant Health Inspection Service


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Date of this Version



Published in Biol Invasions.


Several authors have argued that three separate introductions of roughly 100 individuals were required initially to establish the House Sparrow (Passer domesticus) in the Brooklyn, New York area. We argue that these claims are in error and that the actual record suggests that it is likely the initial introduction of just 16 birds in 1851 was all that was required to establish the species in New York. We further suggest that a similar level of scrutiny of historical records will reveal more examples of misinterpretations and errors, casting doubt on the validity of studies that claim propagule pressure has played an important role in determining the fate of bird introductions.