How do I prevent a magpie from attacking blackbird chicks?

You shouldn’t have taken that young bird that I see in your photo. What you saw was nature. Raptors/Birds of Prey for example take other birds and other wildlife every day. Unless any bird is injured that bird should have been left alone. Sorry about sounding hard. But what you did was wrong!

 community.rspb.org.uk/.../nesting-birds-and-the-law

This was the law about nesting birds and the law in 2010. Nearly all nesting birds are protecting in law. There are occasions when nesting birds including schedule 1 nesting birds can be disturbed under safety and health when for example trees might be in danger such as falling on to someone home or possibly falling on to a railway line as well on to a road!

THOMO said:

Sorry about sounding hard. But what you did was wrong!

A bit harsh Ian on a well meaning poster asking for advise especially given that they had already placed the birds back in the nest!

I’ve noticed a large number of posts in recent weeks  about this same subject, And it had to be said. All wildlife is in danger of attack from other wildlife every day of the year.

You may be misunderstood I love birds and I did not disturb any nest, in fact I returned both displaced birds to the nest. I read the article and found these points:

"Under the Wildlife & Countryside Act 1981, it is considered breaking the law if a person…

• Intentionally kills, injures or takes wild birds
• Intentionally takes, damages or destroy a wild bird’s nest while it’s being used or built
• Intentionally takes or destroys a wild bird’s egg
• Possesses, controls or transports live or dead wild birds, or parts of them, or their eggs
• Sells wild birds or puts them on display for sale
• Uses prohibited methods to kill or take wild birds
• Intentionally or recklessly disturbs any wild bird listed on Schedule 1 while it is nest building, or at a nest containing eggs or young, or disturbs the dependent young of such a bird"

I certainly did none of these. So I did not break any of these rules. Further down I found this piece on nestlings:

"Nestlings

Nestlings are easily identified by their lack of feathers or a fluffy down. Sometimes nestlings fall out by accident and in these instances it’s okay to gently pick them up and put them back but only if they appear strong and healthy. In some cases, a parent will reject a less healthy chick in order to focus its attention on the ones with a higher chance of survival.

If the nestling isn't in good shape, take it to your nearest vet or RSPCA centre."

As I mentioned in my post the birds seemed healthy and strong albeit justifiably scared. Therefore, I correctly returned them to their nest.

Also I should note from this excel sheet from www.nature.scot blackbirds are schedule 3

I accept that,  and you will know very well that we always have questions from new posters who don't know about birds lives especially at this time of year ... there is a nicer gentler way of informing them!

Personally, I think a better way to put it is that intervening in cases like this means more young bird deaths. What the magpie doesn't get this time, it will have to find from elsewhere. What the magpie didn't get has also very little chance of surviving now.

I agree with all that you wrote. However, I also agree with what I wrote, which you didn't comment on. Although Thomo clearly got it wrong re law, and has done so before in various posts, re intervention, taking prey off of natural predators (as opposed to pets) is not best practice.

Yeah I agree with your comment. It was just at the time I didn't know what the best practise was and wasn't really the time to google it, all I saw was some baby birds getting attacked and the first instinct is to protect them. Honestly even knowing the best practise as we are all bird lovers I don't know if anyone could stand by without wanting to do something.