For many species of birds, migration is often a journey fraught with danger. For example, the average songbird may weigh just half an ounce, but this tiny creature travels thousands of miles along routes that are filled with wind turbines, communication towers, buildings, and other potential collision hazards.

The context clues that help identify the meaning of "fraught" include the phrases "a journey fraught with danger" and the description of the numerous hazards that migratory songbirds face, such as wind turbines, communication towers, and buildings. These clues suggest that "fraught" implies being filled or accompanied by something negative, in this case, danger.

The phrase "a journey fraught with danger" indicates that the journey is filled with risks. The mention of hazards like wind turbines and buildings supports that idea of danger.