Everyone knows that caterpillars become butterflies. And birds eat caterpillars and butterflies. After all, they ARE insects!
The host plant is commonly called Butterfly Weed; technically any species of Aesclepias is an ideal host, which includes Milkweed. Consider putting some in your yard to attract Monarchs.
Maybe some folks don't know that climate change is real, but birds certainly do. Now its impact on birds has been proven. A 40-year study by the Audubon Society pinpoints the effects of climate change on various birds. In just 40 years, the centerpoint of the Purple Finches' range has moved 433 miles to the north. Boreal Chickadee, 279 miles north. Downy Woodpecker, 29 miles north. What's more, Audubon's findings are that it takes about 35 years for a bird species to adjust to a new locale.
In a way these birds are fortunate. They happen to have suitable habitat and food sources to the north, so they can move. Birds that don't (Meadowlarks for example) face starvation and extinction.