The only other brassicas I grow are Spinach, Chard and all kinds of kale.
Also uncovered.
Nothing seems to ever attack them, including Slugs/Snails. The empty traps fairly close by show that and never nibbled.
But have in the past grown many other forms of brassica, like cabbage and cauliflower and never had a problem with birds and always grown uncovered.
One of my neighbours grows loads of brassicas (many types of cabbages all the year round and all kinds of cauliflower) and gives me loads as swaps for other crops I grow and share like Turnips rhubarb, cucumber, gherkins and tomatoes.
He does not net them, but does attract the birds as I mentioned above.
My Dad about eight miles inland from me has grown cabbages like Greyhound uncovered and never heard him moan about the birds. He is a big bird feeder and lives in a town suburb area with loads of well established trees and grassed/fielded areas all around his property.
Although we are in a busy coastal town, we ahve plenty of green areas and lots of trees thanks to those Victorian builders. We in our properties have a large fielded area that we all own/share behind our properties that has loads of grassland and very large established trees that is full of all kinds of birds and many nesting. Plenty of other wildlife too frequent and burrow there, like foxes and badgers, plus toads and frogs.
We do live very close to many beach areas within a short walk and of course Portsmouth Harbour is not far away, a short ferry trip over the harbour water.
There are plenty of Crows, Seagulls, Egrets, Swallows, Scoter and other Mediterranean gulls, that do fly up from the coast and often sit on our roofs or high on trees. Never seen any of them every frequent our local trees or gardens.
We also have a large coastal reserve that has many birds and occasionally get some quite exotic ones including more common visits from herons and geese but only ever appearing on our rooftops or high trees.
So quite a mixed wildlife.
Plus, another thought Myself and moat of my immediate neighbours do all own cats and some own Dogs and Cats, so another great deterrent for keeping them off the ground I'd assume.