It is warmer there. Man made materials absorb more heat and radiate that heat back out more slowly. The warmth also helps plant growth so yes, the vegetation close to the road probably is yummier. Or at least stays greener longer into fall and probably turns green sooner in the spring too. In the fall grackles all move from the countryside to the city around here. They roost in trees or on power lines around parking lots which are warmer than fields. The birds like that warmth from the asphalt and car engines.