This is our second Pine Siskin with a deformed bill. The first, seen at Davis Mountains State Park, was clearly an injury. Its upper mandible was missing.
This one, from our trip to South Llano River State Park today, is of a less obvious cause. It appears to be a growth defect with both mandibles growing too long and curved downward. When we first saw it in full profile, we had the strange sensation of being in Hawaii seeing a honey creeper. Either the lower mandible has continued to grow even longer (that is not a tongue) or the corresponding extension of the upper mandible has broken off. The bird was feeding at the thistle seed feeder but I was not able to establish whether it was able to pull seeds through the mesh or just feed in the tray.