After a cold or rainy spell if the sun comes out they will sing. Makes them happy, too.
It is part of their communication thing. They, the little warblers, haven't started migrating just yet. Won't be too long though. Every morning the Wrens in the back yard welcome us and ask for food by singing. When the sun came out a bit ago, the lesser goldfinches were singing their little hearts out. We are probably one of the few houses in this subdivision feeding and putting out water for them. Have to empty the water dishes every couple of hours as it freezes over. Everyone including the Cooper's Hawk has been in to eat - course he was looking for another bird - got a white-winged dove I think.
Lots of mating has started around here, but it is with the birds that mate early - hawks, owls, wood cocks. Liz had shots of Black Crowned Night Heron with a streamer on the back of his head - part of his nuptials prior to breeding. So some are prepping and getting ready, others haven't crossed the Gulf of Mexico yet...may 8-10 weeks out for them coming over.
That's my opinion and it is given free of charge and can be considered as worth nothing!!