Based on the lines of the poem provided, a possible central idea of the poem is that birds are more free and happy when they are near their homes, whereas humans may feel more free when they are far from home. This idea is suggested through the contrast between the experiences of humans and birds in the poem. Humans may enjoy being far from home and driving in open country, but the poem suggests that birds are happier and freer when they are near their homes and are able to hear only their own songs. This central idea could be explored further through the use of imagery, figurative language, and other literary techniques in the poem.