Bird Catcher
The bird catcher is the protagonist of the poem and is suffering from unrequited love. He is in love with the squire's daughter, but she is unaware of this. He then releases larks, a symbolism of daybreak, to symbolize his love for her. The fact that the larks remain "Singing about her head" indicates that he has hope that she will one day hear his message and return his love.
Squire's daughter
She is the love interest of the bird catcher, but unfortunately she does not return his love, assumedly due to the class difference between the two. She is either ignorant of his love as she simply rides past him, or she is truly unaware of his love for her.