Amazing footage shows two birds building a nest from scratch in just 15 days.

Marta, 34, who wishes to keep her surname private, first spotted two western house martins setting up shop on the wall outside her office window on May 14.

Marta documented the building process as the birds used dirt and their own saliva to construct the home.

The birds will continue to live in the nest, as long as it goes undisturbed, until the season is over in autumn.