It should be drawing their hearts and feelings to all that is lovely and good. This is where the wonderful literature comes in. It gives opportunity for language development and woos the heart. As for chronology, youngsters don't really think chronologically. This type of thinking is something they grow into.
Young folks are far more oriented to people than to eras.
That's why we read tons of biographies and historical fiction. We want them to explore their world deeply and intimately, building relationships along the way. By the time they reach 12or so, they're ready for a more abstract, chronological approach. Your children are sending strong signals when they remember what you did in the bird unit. As you noted, a lot of it had to do with the fact that it was hands-on and related to their world.