Cat watching nest - how to avoid disaster

A lovely blackbird couple are on their third nest location in our garden already this year. Unfortunately their previous nest was discovered and attacked by a neighbour’s cat and a nestling fledged early as a result and died a couple day’s later. 

Fortunately their current nest location is better protected from cats as it’s just below the roof of our tall pergola. However, when the time comes for the nestlings to fledge (they’re currently about 1wk old), I’m very worried the cats who have already found their new location will immediately go for the fledglings on the ground. Especially as baby blackbirds cannot fly straight away. 

is there anything I can do to stop this from happening? It’s so hard to watch the babies perish on the ground and not be able to do anything about it Pensive I would greatly appreciate any and all advice. I work from home so can be quite vigilant.