# I will spread my net over them
This is a way to catch birds. Yahweh continues to compare the people of Israel to doves. When they go to Egypt or Assyria for help, Yahweh will punish them.
# I will bring them down like the birds of the sky
"I will hunt them like birds" or "I will catch them like a hunter catches birds"
# in their flocking together
"when they gather together"