Average numbers of wetland birds Time (years) Start-up Sample estimates, taken at approximately yearly intervals, of the average numbers of wetlands birds in the vicinity of the aquaculture facility before construction and after start- up of the facility (filled symbols) and an average of three comparable wetlands in the area but at some distance from it and not affected by the facility (open symbols). Time of start-up is indicated by the downward-pointing arrow. (Error bars are not shown for simplicity.)