When we think about the spread of Influenza A viruses in birds, we most often will point to migrating bird as the source of the disease. During their flight over long distances these birds excrete their poo which contains large amounts of viruses. This in turn can infect domestic poultry such as chicken.
There are however other species of birds that are susceptible to the various Influenza A Viruses. We have already mentioned sparrows and penguins, but now reports have been published of two outbreaks in Saudi Arabia of Influenza A Virus in ostriches.
Earlier outbreaks of Influenza A viruses in ostriches occured in South Africa. Tests revealed that the animals were infected with Influenza A(H5N2) Virus. The outbreak strains in 2011 had no genetic relationships to the previous 2004 and 2006 Influenza A(H5N2) outbreak viruses.
It occurs to me that possibly every mammalian or avian species is at risk of getting infected with the Influenza A viruses and can therefore act as a mixing vessel. New or even slightly changed viruses may unexpectedly appear from every part of the globe.
 Ismail et al: Characterization and phylogenetic analysis of a highly pathogenic avian influenza H5N1 virus isolated from diseased ostriches (Struthio camelus) in the Kingdom of Saudi Arabia in Avian Diseases - 2014
 Abolnik et al: Molecular analysis of the 2011 HPAI H5N2 outbreak in ostriches, South Africa in Avian Diseases - 2012