What is a common characteristic of wines that undergo secondary fermentation in the bottle?

Wines that undergo secondary fermentation in the bottle typically exhibit bubbles, which is a defining characteristic of sparkling wines. This process, often employed in the production of traditional sparkling wines like Champagne, involves adding a mixture of sugar and yeast to the base wine before sealing the bottle. The yeast consumes the sugar and produces carbon dioxide as a byproduct, which cannot escape because the bottle is sealed. As a result, the gas dissolves into the wine, creating the effervescence associated with sparkling wines. The presence of bubbles is a clear indicator that secondary fermentation has taken place, distinguishing these wines from still wines, which do not have carbonation and come from a different vinification process.