LitCharts assigns a color and icon to each theme in The 5th Wave, which you can use to track the themes throughout the work.
Trust and Belief
Survival and Perseverance
Warfare and Dehumanization
Family
Summary
Analysis
Still traveling around noon in the present, Cassie sees a shadow and thinks it’s a drone, but it’s just a bird. She hates that the 3rd Wave has made her suspect even birds now.
This is another passage that captures Cassie’s distrust, showing how she has become paranoid not just about other humans but about nature itself, all as part of the aliens’ plan.