Put up a bird feeder and plant a hedge or let ivy scramble up a fence.
Hi, the draw to my garden is a stone trough full of water, even a shallow bowl would add a new dimension.
If you have any shrubs or hedging near the trees, place the feeders close to those as birds will be more likely to use them if they can quickly flit into a bush etc to hide when a predator is around (cats, sparrowhawks etc.) Hawthorn is perfect.
PS, it may take a few weeks for birds to discover the feeders so be patient.
In fact, if you can make it cat-proof that's even better.
All the above OP, Laurel, pyracantha even conifer trees we have Goldcrests in. Our problem is that the windows all round the house get banged into, larger birds survive but the smaller ones end up having to get buried the window cleaner said he is amazed at the bird dust marks on most of the window. We have put plants and structures to mask the reflection, helped but not a lot.
Birds love dried mealworms - although they can be a bit expensive to buy. Here, they seem to smell them quite a distance away. They are mad about them, irresistible. I have them in a wire peanut feeder and it has attracted a mix of small birds I never used to see in this small town garden. A shallow dish with water is also a draw.
Also keep the feeders about head height, it gives the birds warning if the cats make a leap from under the bushes. I was like firecracker until i moved the feeders higher, my neighbours cat just wanted to catch them