In our human world, we've become stewards to many animal species.

Among the most beloved are the migratory bird species that travel great distances across the globe.

Where do birds come from and where do they go? That's kind of a fundamental question that has intrigued scientists and people probably from the beginning of time.

That's Judd Howell, Director of the US Geological Survey Patuxent Wildlife Research Center. Howell told Earth & Sky that bird tracking technology has come a long way. Once upon a time, satellite transmitters were so heavy, that only big animals like polar bears could be fitted with them. The bears could be tracked to within several kilometers. Now, birds the sizes of geese or ducks can carry the transmitters on their global treks, and they can be tracked to within a few meters.

Well, if we understand what their habitat needs are, I mean, a habitat is the place where an animal lives, and it gets its food there and its shelter there and it reproduces there. And if we can understand, you know, what those needs are and make sure that those needs are being met then you can be reasonably assured that you'll be able to keep that species going in the wild.

Practical applications for humanity include monitoring where wild and domestic birds meet. Howell said one such program in China relates to the spread of avian flu. Our thanks today to NOAA - the National Oceanic and At/mospheric Administration. We are Block and Byrd for Earth & Sky.