Golden-crowned Kinglets are tiny birds, not much bigger than Ruby-throated Hummingbirds, that can withstand extreme cold.
Most Golden-crowned Kinglets, breed across Canada. Then they migrate to spend winter across much of the US, including the upper mid-West. Also, there are populations that are year-round residents in higher elevations of the Appalachian Mountains & mountainous West. This means they are never quite out of range for seasonal cold weather.
They have many cold snap adaptations, including maintaining a high body temperature of 111 degrees. This requires a lot of fuel. This would seem problematic since insects are 90% of their diet, even in winter.
How they cope during the winter shortage of insects puzzled scientists for years.
Until it was discovered in the mid-1990s that they were experts at finding & eating overwintering Geometrid moth caterpillars – inchworms. Specifically the one-spotted subspecies that is abundant across North America because they have multiple species of host trees.
The trick is finding them. In the winter when trees’ growing season ends and their leaves have dropped, these inchworms attach to a branch or ‘leaf litter’ and transform into pupae that look just like a twig. Except to Golden-crowned Kinglets who gobble them up by the gram.
Want to help these little frenetic paced birds out? Leave the leaves. #leavetheleaves
