I'm very happy to hear they like treesMake sure the nectar is close to the feed you're having a problem with and also pebbles and things in the syrup so they have something to land on without drowning.
I've put things close to the hive and even planted beds of flowering plants next to the hives for them and they get ignored. When the foragers come out of the hive, they make a 'bee line' for distant lands.
On the topic of bees feeding on trees. The famous and very tasty Tupelo honey comes from very large trees.

When I fed the birds this morning the bees were not out, maybe to cold and windy? I am going to try to plant some flowering shrubs soon. I hope...
Thank you for all your help Hagar3