There is a source which is important in the search for Irish birth places. This is the land grants for the Western Canadian Provinces. Canadians and Americans need to remember the border between the two countries is very long, and very open. Families went back and forth whenever land opened up in a border state or province. Often people stayed for generations. Others would move on.
The National Archives of Canada (NAC) has indexed to the Letters Patent issued by the Lands Patent Branch of the Department of the Interior: www.collectionscanada.gc.ca/databases/western-land-grants/index-e.html The database includes Alberta, Manitoba, Saskatchewan and the railway belt of British Columbia. This is just the index, which is very basic. The homestead applications themselves, which often provide birth place of the applicant, are held at the provincial archives. The homestead applications and index for Saskatchewan are on microfilm at the Family History Library (FHL). A microfiche index to the Manitoba grants, and the grants and index for British Columbia are also at the FHL.
The Alberta Genealogical Society: www.abgensoc.ca/patent/index.htm has an extended online database which includes references not found in the NAC database.
The provincial archives all have quality and helpful archives: Provincial Archives of Alberta: http://culture.alberta.ca/archives/ The Archives of Manitoba: www.gov.mb.ca/chc/archives/index.html and the Saskatchewan Archives: www.saskarchives.com/collections/land-records has an entire section and database dedicated to the topic of land. The British Columbia Archives has an online guide to its homestead records: www.bcarchives.bc.ca/BC_Research_Guide/BC_Pr_Emptn_Hmstd.aspx
This is an important topic as families moved from eastern Canada to western Canada, and north from the United States. Even if your family did not directly receive land in Western Canada, then by researching a cousin or sibling who did, may still prove where the entire family was from in Ireland.