Peppered moths show NS ... whether you like the example
or not ... it shows it ... by observation.
The galapagos finches show the results of NS, and studies
have been reported on this site (so I cannot claim them
to be accurate) that say if you remove the finch population
to another location the 'specialised' beak trends tend to fade
out of the population. It's an observation.
Darwin saw that different creatures, in different parts of
the world shared strikingly similar features if they shared
similar habitats.
He inferred that something about the habitat must pressurise the
creatures into developing these features. This inference
is supported by observation.
Like it or not NS is an observation of nature.