Bird feeders and cabbage whites

When Chris Packham came on our wildlife day he put 3 bird feeders up into an Oak tree on the site.
It has taken 2 weeks for the birds to get used to these feeder but now they have found them they are emptying them out in a couple of days. The most important thing is to keep them filled up as now they have found them we want to keep them interested in the site as they can be great predators and with the amount of cabbage white butterflies about we will need their help and assistance in controlling the caterpillars that are about to invade us.