The most infected species of H5N1 highly pathogenic avian influenza (HPAI) broke out in Qinghai Lake in 2005 was bar-headed goose ( Anser indicus
). To investigate the immune status to H5N1-AIV of bar-headed geese in Qinghai Lake National Nature Reserve, 68 ejected eggs and 125 in-nest eggs of the breeding colony were collected in spring 2008, and haemagglutination inhibition (HI) was applied to analyze their yolk MAb (IgY) to H5N1-AIV. The results revealed, three years after the outbreak of HPAI in 2005, 26.5% to 35.2% of breeding pairs of the bar-headed geese breeding on Bird Island in Qinghai Lake may have acquired anti-H5N1 AIV immunocompetence. In addition, we analyzed the relationship of MAb titers of the nest-eggs and the nest density, and found the significant correlation between them (r
=0.000). It is likely to be more adaptive that the MAb transmission pattern in the breeding colony with high breeding density.