As were the Ch. of England clergy as well. The use of "Father" by Anglicans was slow to develop and came about as a result of the Oxford/Tractarian movement of Pusey, Newman and others in the 19th century. It was controversial at the time, and still is not used in the low church wing of Anglicanism.

 As Bill T. pointed out, high church/Anglo-Catholic places call women clergy "Mother", which is used by you good RC to describe the head sister (religious order) as I understand it.