Cold

Aldo comes inside when the outdoor temperatures dip below 10°F, so he has been in the office a lot recently. When people ask why, they often nod and answer their own question: "oh, because he's so small!" But size can't be the only way to explain this bird's winter hardiness. 

Both my daughter and my cat delighted in watching chickadees at our bird feeder last weekend. Weighing in at just a half-ounce, chickadees are 1/7th the size of Aldo the American Kestrel. Yet they survived even through our recent -30°F nights. 

My whole family was enthralled with watching the bird feeder at breakfast!

Chickadees have fascinating strategies to cope with Wisconsin's winters. They ensure a food supply by hiding seeds in the fall, and enlarging the memory portion of their brain (hippocampus) by 30% to remember where those seed caches are located.

Small owls, about the same size as kestrels, also overwinter here. They can locate prey under a blanket of snow with their amazing hearing and can feed themselves even in the depths of a Wisconsin winter.

Kestrels like Aldo don't have those unique adaptations. Kestrels eat small birds, rodents, and insects fresh, so chickadee-like food caches are not an option. And without an owl's ears, they would have a hard time finding animals to eat under the snow. Access to food, rather than size, explains their migratory nature. 

Even though Aldo has a consistent supply of food at the Museum, his species just isn't built to weather those extra-frigid temperatures. So he comes inside in our best effort to keep him happy and healthy.

Read more about how birds survive the winter with this fascinating article:

How Do Birds Survive the Winter? Story by Bernd Heinrich