The class derives its name from large birds found in Canada and was designed by the RCN as a replacement for the remaining Second World War-era Fairmile motor launches used for coastal patrol.

[3] The Bird class were powered by diesel engines creating 1,200 brake horsepower (890 kW) connected to two shafts.

Blue Heron commissioned on 30 July 1956 at Orillia, Ontario and was allocated to the Royal Canadian Mounted Police Marine Division based at Halifax.

[3] In 1961, Cormorant, Mallard and Loon were assigned to Atlantic Command as harbour patrol craft.

[4] In April 1961, Mallard was deployed to rescue the crew of the fishing vessel Ocean Wave which had run aground off Nova Scotia.