1)
What is the comparison to a bird?
1.
Ibn Ezra: All my crying is because I am seized like a bird.
2.
Palgei Mayim: A bird is trapped via wheat kernels (the trapper puts them out so it will come to eat them). So Egypt trapped me via the wheat that they sold there; we broken in an evil trap there.
2)
Why does it say "Chinam"?
1.
Ibn Ezra, Ri Kara: They are my enemies for no reason. I did not sin against them!
2.
Palgei Mayim: Yakov and his sons did not descend to Egypt due to sin 1 .
1
Against people. It was due to Avraham saying "ba'Mah Eda" (Bereishis 15:8). (PF)