Whether it is the Marsh Wren singing to attract a mate (or more - they are polygynous). It appears that their complex vocalizations are used to attract mates and establish territories.
The Red-winged Blackbirds and Song Sparrows gathering nesting material.
The Black-capped Chickadees sharing a meal
To the Tree Swallows mating on the top of the snag they've selected for this year's nest. I especially like how he's pulling on her head feathers.
To the Canada Geese who are faced with the challenges of raising their new-born chicks in a tough cruel world.