Nevermind, I found the answer myself. I suppose by this we are both right.
"Some people believe that the oil of the preen gland has little to do with 'waterproofing' feathers, the main function of the oil being to keep the feathers supple. Freethy, in his excellent book 'How Birds Work', explains that preen gland oil is not the only defence against water-logging; constant attention to zipping the barbicelli of the feathers together is also important. However, one only has to look at ducklings to see that preen gland oil does have some function in repelling water. Ducklings reared under a mother duck have a certain extent of natural water-proofing from contact with her feathers. The contact maintains a good down structure as well as spreading preen-gland oil on ducklings when they are only a few days old. Ducklings reared without a mother are not nearly so waterproof. The debate about wet feather is not a new one. At some point, a review of earlier literature on the subject will be published by the CDA. "
"Some people believe that the oil of the preen gland has little to do with 'waterproofing' feathers, the main function of the oil being to keep the feathers supple. Freethy, in his excellent book 'How Birds Work', explains that preen gland oil is not the only defence against water-logging; constant attention to zipping the barbicelli of the feathers together is also important. However, one only has to look at ducklings to see that preen gland oil does have some function in repelling water. Ducklings reared under a mother duck have a certain extent of natural water-proofing from contact with her feathers. The contact maintains a good down structure as well as spreading preen-gland oil on ducklings when they are only a few days old. Ducklings reared without a mother are not nearly so waterproof. The debate about wet feather is not a new one. At some point, a review of earlier literature on the subject will be published by the CDA. "
