Do 2 swallows make a summer?

After an absence of about 2 years the swallows are back in the garage at work. They have been nesting above the big door for the last few years, and on a couple of occasions have even raised 2 broods during the summer. It's always lovely to see the little ones; once they have fledged they fly in and out of the door and it can be an anxious time when we count them back in and one is a little bit slow in returning! For the last 2 years however, we have had a big problem with pigeons roosting in the garage and the swallows, even though they came back after the winter, didn't nest. This year though there seems to be no sign of the pigeons, so welcome back little swallows! We are looking forward to seeing how many little ones are fledged this year.