This video is about a house martin nest on a balcony of an apartment building in Poland.
Translated from BirdLife in the Netherlands today:
Between the 1960s and 1980s, the house martin populations in our country decreased by about 70%. From 1990 on there was a slight increase. Despite this attention to their protection needs: for alleged nuisance their nests are too often removed or they are prevented from nesting in many ways. To help house martins with additional nesting opportunities therefore in the Netherlands since 2008 139 house martin ‘dovecotes’ have been made available.
Each year, these cotes are monitored. In 2015 house martins nested in 21 cotes. Thus, the occupation increases slowly, from 2.7% in 2010, 4.5% in 2011, 8.5% in 2012, 9.8% in 2013 and 12.3% in 2014 to 15.1% in 2015. Because once occupied cotes usually during following years remain inhabited and every year a few cotes will get new inhabitants it is expected that the occupancy will continue to increase in coming years.