They will bay when they detect an interesting scent but they may also become problem barkers due to boredom or separation anxiety. (thesprucepets.com)
Females, however, may become problem barkers in order to protect their den. (sheppardsoftware.com)
One of my dogs (who used to be a serious problem barker) used to love this game and would sit for hours looking out of the front window, silently observing passersby, just daring them, or maybe willing them, to step on our property. (dogstardaily.com)