Looking for information on James Spear, Skerry Parish

James Spear, my great grand-father, was born in Rathkenny Town Land, Skerry Parish, in 1836.  He was the son of John Spear, a tenant in Rathkenny, who is listed in the 1861 Griffith's Valuation.  In 1865, James Spear (re-spelled as Speers) emigrated to the US with his wife Elizabeth (McClure) Spear.  I am searching for information about the immigration of the Spear family from Scotland to Ireland.  Baptismal records show that James was baptized at the Presbyterian Church in Ballymena.

John Spear, James' father, was married to Isabella Strahan in Rathkenny.  John (b.? d 1887) was the son of Robert Spear and Sarah Henry, presumably of Rathkenny.  Robert was born in 1780 and died in 1862.  I have no record of where he was born.