Why Do Birds Migrate Like This?

Each autumn, billions of birds migrate from higher latitudes to the tropics. Instead of flying straight, they often take zigzag routes to utilize wind patterns, which helps them travel faster. Birds prefer land routes to avoid water, with small birds avoiding open seas and larger birds using thermals for lift. These migration patterns bring birds together at key hotspots along their routes.

What are thermals and how do they assist larger birds during migration?

What happens at key straits and land bridges during bird migrations?