McDonald's (NYSE: MCD) is on watch Wednesday following news that it might be losing ground in one of its key operating segments: breakfast.

According to the NY Post, Yum! Brands' (NYSE: YUM) Taco Bell is making headway in the early-hours edibles market. The report cites weekly traffic analysis from Foursquare.

Data shows that Taco Bell generated 20 to 25 percent more traffic to its chains after adding all-day breakfast to its menu, versus just a 9 percent increase at McDonald's.

One Foursquare analyst commented, If McDonald’s bump acts similarly to Taco Bell’s, where the 25 percent became 7 percent as the novelty wore off, McDonald’s will likely fade to between 1 percent to 2 percent within a couple of months.

Shares of McDonald's are flat Wednesday after closing down about 0.6 percent yesterday.