Migratory Birds in the Northern Hemisphere Most Likely Head to Tropical

Multiple Choice

Migratory birds in the Northern Hemisphere most likely head to tropical overwintering grounds because ____.

A) they are looking for appropriate sites for egg-laying
B) of seasonal changes in the abundance of predators
C) they are looking for appropriate breeding sites
D) of seasonal changes in food supplies
E) they are ectotherms and cannot withstand cold temperatures