Food availability: Redwings are primarily insectivorous, and their diet consists mainly of insects, berries, and fruits. During the breeding season in the northern parts of their range, there is an abundance of insects and fruits, which provide them with ample food resources. However, as winter approaches, food becomes scarce in these regions due to the colder temperatures and reduced insect activity. Therefore, redwings migrate south to warmer areas where food is more abundant, such as the Mediterranean region, North Africa, and the Middle East.
Harsh winter conditions: Redwings are not well-adapted to extreme cold temperatures and snowy conditions. They are small birds with a high surface area-to-volume ratio, which makes them more susceptible to heat loss. Additionally, the snow cover in their breeding grounds during winter can make it challenging for them to access food resources. By migrating south, they can avoid these harsh conditions and find more suitable habitats for survival.