Strengthening the nest or still building? I think he is just adding because she is already spending a lot of time in the nest. He brought this length of polypropelene line and went to work. I have seen several nests utilizing this human trash. I saw a fledgling Great Kiskadee on Kennedy Loop today and another nest with a female inside. I saw a GK chase a Yellow-headed Caracara that obviously got too close, and as soon as he was finished a Tropical Mockingbird took over.