- [Narrator] In the heart of this grove,
half a billion monarch
butterflies lie sleeping.
They have traveled from as far as Canada
to escape the cold northern winter.
How they return to this
exact spot is a mystery.
Like the butterflies,
hummingbirds feed on nectar,
so our spy isn't seen as a threat.
While resting, they cluster together
to conserve precious warmth.
But as the winter ends, the
sun warms their fragile wings.
Once they reach a critical 50
degrees, they start to fly.
As the day warms, the
forest comes to life.
(sparkling orchestral music)
Spy humming bird won't harm
these delicate butterflies.
Its moving parts are
shielded to keep them safe.
Butterflies can even
safely land on its wings.
It begins to capture
something quite extraordinary.
What starts as a trickle
soon becomes a stream.
Then grows into a cascade.
A spectacle that has rarely been filmed.
And our spy is harmlessly
in the very heart of it.
(bright orchestral music)
Beauty also lies in the detail.
(delicate orchestral music)
