The "true sparrows", the Old World sparrows in the family Passeridae, are small passerine birds. The differences between sparrow species can be subtle. In general, sparrows tend to be small plump brownish or greyish birds with short tails and stubby powerful beaks. They are primarily seed-eaters, though they also consume small insects. A few species scavenge for food around cities and, like gulls or pigeons, will happily eat virtually anything in small quantities.