What are the themes of competitions that have corresponding host cities with more than 1000 residents?
SELECT T2.Theme FROM city AS T1 JOIN farm_competition AS T2 ON T1.City_ID  =  T2.Host_city_ID WHERE T1.Population  >  1000
themes of competitions = T2.Theme; competitions with host cities having more than 1000 residents = WHERE T1.Population > 1000;