Overview of seven studies with at least 5,000 birds collected over at least five sampling events.

1Unpublished data provided by Martin Gilbert 10 February 2013.
2Richness estimated based on data thru 2007, population prevalence based on data through 2009.
3Sampling method was not reported but based on historical sampling patterns suggest it was cloacal.
4Provided by Vincent Munster 21 December 2012. These data excluded Ottenby Mallard data reported under Sweden.
5Extended data provided by Meng-Chu Cheng 12 November 2012. Bird families based on published data from Cheng et al. 2010.
Positive samples used to calculate prevalence (positive/total) may not all have been fully subtyped.