WORTH NOTING ON TV

* WEDNESDAY

The New Explorers With Bill Kurtis (PBS, 8-9 p.m.): Each year, bird-watchers spot fewer North American songbirds. This episode of the science-adventure series, entitled ''On a Wing and a Prayer,'' probes reasons behind the birds' decline in population. The crux of the problem appears to be forest fragmentation, for which the program explores several solutions.

Understanding: Television (The Learning Channel, 9-10 p.m.): Take a step back from usual TV-watching to learn how all those images pop up on your screen. This program traces the technological history of television, using the Daytona 500 as an example of how broadcasting works. There's also a look ahead to the digital revolution and 500-channel universe.

* THURSDAY

Fat Man in France: a Journey With Tom Vernon (PBS, 8-8:30 p.m.): This weekly, six-part series follows the stout traveler as he bicycles through the French countryside. In this first episode, Vernon visits Brittany, where Celtic traditions persevere in quaint towns.

Following this program is The 3,000 Mile Garden (PBS, 8:30-9 p.m.), another weekly, six-part series. This one shares correspondence on gardening between Leslie Land, an American food writer and editor, and Roger Phillips, a British horticulturist and writer. The first episode shows Phillips utilizing hot mulch to cook a New Year's ham, and Leslie remembering summer with garden potatoes and canned tomatoes.

Mickey's Christmas Carol (CBS, 9-10 p.m.): Mickey Mouse, Scrooge McDuck, Donald Duck, and Goofy star in Disney's animated version of Charles Dickens's yuletide story. The hour broadcast also includes two other Disney holiday cartoons: ''Pluto's Christmas Tree'' (1952) and ''Donald's Snow Fight'' (1942).

Please check local listings for these programs.