Do you know the approximate length? Since you've seen large roundworms, they can grow up to almost 5 inches. There are two reasons why large roundworms are excreted (other roundworms as well.)
They are either dead or dying and are excreted in feces. OR, the bird is overloaded with worms and they have nowhere else to go but out the rear end and are excreted in feces. They will die because they cant survive outside the host.
Here's a pic of a cecal worm by comparison, hopefully it'll help you identify what type of roundworm was excreted in your birds. In any case, the Safeguard will take care of both types and other unseen types of worms as well, just do the 5 day dosing.
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