The least sandpiper is named as such because as I've said it's the smallest shorebird in the world, with its scientific name "minutilla" directly translating to "very small" in Latin; essentially, it's the "least" or smallest among the sandpipers.
The bird was picked up pretty distant in the thick vegetation before all the birds were spooked and took to the wing where it was picked up feeding opposite the Quantock Hides, just behind the main scape.