I am not sure when we start the countdown, aka Hatch Watch, for the eggs. Most of my reference books are for North American birds. If we use May 8 as day 1, then we can start watching for chicks 24 days later, according to the information you have posted.
Video: Rooftop Oystercatcher Incubates her EggsKjellaug and her mate Kjell are back at their rooftop nest in Bergen, Norway. When Kjellaug returns to the nest, she gives the cam a few good pecks before settling down on her eggs.
Recorded at 7:37 PM local time
Norwegian name: Tjeld
Haematopus ostralegus
From the website:
The Eurasian Oystercatchers usually breed on the ground in open areas. The concept of roof-breeding is known from different sites. Aberdeen in Scotland is known for its population of roof-breeding Oystercatchers, counting about 230 pairs in 2004. In other countries the phenomenon is more uncommon, but is recorded (at least) in the Netherlands, Belgium, Finland, Latvia, Germany and Norway.
"The Oystercatcher is one out of very few shorebirds that actually feed their young. This is also a condition for successful breeding on roofs up to 30 meters above the ground. In Bergen the adults feed in the parks near the building where they breed, and bring the food for their young. It seems that they mainly deliver Earth-worms Lumbricidae sp. to the chicks. The chicks stay on the roof until they are more or less able to fly.
Oystercatchers have been breeding on roofs in Bergen city, western Norway the last five years (since 2000). In this period at least three different roofs have had breeding birds."
http://tjeld.uib.no/