You can see where birds have pecked irregular shaped holes into the latex chinking looking for insects and even where they chewed into the backer rod.
Birds can hear the insects moving within the log work and they are trying to reach them. The insects have either found within the logs soft, moist wood to nest in and hatch their young or are feeding on the wood itself.
The insect infestation of the logs needs to be treated first. Look for other small holes (accompanied by fine sawdust) in the log work. Using a syringe, inject the holes with an approved insecticide. Plug the holes with caulking or a mixture of wood glue and sawdust. For more information on the prevention and treatment of insects see Chapter 4: Insects starting on page 30.
Once the insect problem has been dealt with, fill holes with similar caulk or chinking to seal them from future infestation and moisture infiltration.
Unlike mortar chinking, synthetic caulk and chinking will adhere perfectly to old caulk or chinking as long as the surface is dry and free of dust and debris. Apply a small amount of new chinking over the holes and spread out with a foam brush to form a seamless patch.
Monitor the chinking and logs over the next few months to see if any more holes materialize. If so, repeat the treatment until they stop appearing. Typically, once the insect problem has been effectively dealt with, the birds should leave the chinking alone.
Reprinted from the Log Home Maintenance Guide.