Monarch butterflies threatened.

From ABC News:

When the sun comes out in the mountains of central Mexico, hundreds of millions of tiny, orange monarch butterflies fill the skies.

[...] It's not just the sheer number of butterflies that is astonishing, it is the density of them in the landscape. It is as if the trees are covered in a bark of butterflies. Butterflies fall from the trees, landing on our arms and feet.

Unfortunately, some of the residents of the region have not returned the welcome. Though monarchs fill the skies, they are facing a dire threat, because the forests where these wonders of nature make their winter home is disappearing, the trees being chopped down by illegal logging operations.