When we get ready for a trip, we pack a suitcase. When birds prepare for their migration trip, they pack on the fat! Birds migrate to find the most abundant food sources. As the length of daylight changes, the birds prepare with a few physical adaptations. Their hormone levels change now that their breeding season is over, and their sexual organs shrink. This change allows for them to pack on extra fat to provide extra energy for their journey. For example, the Ruby-throated Hummingbird nearly doubles its body fat just a week or two before they leave.
Birds also often replace some of their feathers. Old, ragged feathers may hinder them in flight, so they grow new feathers in a process called molting. Birds also make some dietary changes. As the availability of insects decreases toward the end of the season, some birds, like the Gray Catbird, add berries to their diet to help add to their fat reserves. We can help them on their journey by keeping our feeders full and adding native plants to our gardens.
By Guest Contributor MELISSA BLOCK