Excretion of LPAIV H13N2 and H16N3 by black-headed gulls, shown per individual bird. Virus excretion was based on the AUC value for viral RNA (i.e., CT value determined by M-RT-PCR). Black indicates the first inoculation, gray indicates the second inoculation, and white indicates the third inoculation. x, the bird died and was excluded from the analysis; a, the second inoculation of groups 5 and 7 was unsuccessful.