breeding pairs

Since Jan 8 the pair close to the house have been in attendance on an every other day basis , which by 28th became a daily event. Since 2 Feb they have been roosting close to the nest also, and Tuesday the 8th I observed the pair repairing and adding to the nest. On this basis I visited 2 other nests and found pairs either perched near to and flying close to their nests. This is some 2 weeks earlier than what I have observed in the past. The 3 pairs are old hands not first year pairs. Indication of an early breeding season or something else?