Often, the migration route of a long-distance migrator bird doesn't follow a straight line between breeding and wintering grounds. Rather, it could follow an hooked or arched line, with detours around geographical barriers. For most land-birds, such barriers could consist in seas, <answer>large water bodies or high mountain ranges</answer>, because of the lack of stopover or feeding sites, or the lack of thermal columns for broad-winged birds.
What geographical barriers to land birds try to avoid?
large water bodies or high mountain ranges