Mortalities in colonial seabirds associated with a highly pathogenic H5N1 avian influenza virus in Quebec

Last week mortalities of several northern gannets were reported in the Magdalen Islands, Quebec. Conservative estimates suggest that more than a hundred gannets died over just a few days. Unusual mortalities of common eiders and black-backed gulls were also documented this week in the St. Lawrence Estuary, Quebec.

This observation indicates that this virus, which was first observed in migratory birds, is now well established in the nesting sites of colonial seabirds. The high mortalities documented so far suggest that these species have a high susceptibility to this virus. Aggregation in bird colonies during the nesting season undoubtedly favours the transmission of the virus.

While the impact this emerging virus will have on northern gannet and common eider populations remains uncertain, this new cause of mortalities adds to the problems seen in recent years in several colonial bird populations. In fact, northern gannet populations present in Quebec have experienced a significant decrease in their productivity, likely due to changes in the distribution of Atlantic mackerel, likely associated with climate changes. Although populations of common eiders in Quebec seem stable or even increasing, decreases in abundance have been documented in several colonies in Maine and Nova Scotia, suggesting a potential decline of the species. Monitoring the mortalities associated with this virus in these populations of birds will allow us to better understand the potential effect of this virus on the dynamics of these populations.

Stephane Lair

CWHC-Quebec

Pictures : Nestling northern gannets