Donell asked what attracts Canada geese to a specific field or patch of lawn one day and not the next.

It's all based on habitat needs, said Rocky birds columnist Mary Taylor Young. Canada geese are grazers, so they pick the spot that appears to offer plenty of grass; they also like to be near water so they can leave dry land for protection from predators.

They pick a different spot the next day probably because they've grazed over the previous spot.

And they stay in a pack because they're social animals and there's safety in numbers, Young said.

Here's a new challenge:

Why are there almost no sidewalks in the Hilltop neighborhood and the streets north of the East Sixth Avenue Parkway? Congress Park was built earlier, and there are sidewalks on each street. - Jim

Know the answer? Post it on the Ask! blog, blogs.RockyMountainNews.com/denver/ask, or e-mail rudeenm@RockyMountainNews.com. While you're on the blog, check out the other questions on the Ask! home page, or post one of your own by clicking on the link to the right on the page.