I have three 60 year old black walnut trees. If you peel back the husks when they are at that stage where they are really black and gooey and stain everything that comes in contact with them,you will find that they are filled with dozens of insect larva that resemble maggots. Once my girls discovered that, they picked the husks off like crazy. Their beaks and faces were stained for weeks. I was most worried that the high levels of tanic acid would give the eggs and off color and/or a bad taste, but neither concerns seemed to be warranted.
Although my girls really seemed to enjoy picking the little buggies out of the husks, I never saw them pick at any of the cracked open pieces that the squirrels dropped. Like the previous poster, I finally decided that the biggest threat was getting killed by falling walnuts. So when they were falling the hardest, I confined the girls to their covered run most of the time.
