What is "Ke'as"?
Rashi: It is a species of bird 1 . Radak - it is Kik mentioned in the Mishnah (one may not light Ner Shabbos with Kik oil - Shabbos 2:1).
What is the comparison to "Ke'as"?
Rashi: So we wander from our place to go to Galus.
Radak #1: It is a wilderness bird with a lamenting voice. My voice was like its.
Radak #2: In Galus, I consider myself as if I speak with the birds that dwell in the Midbar, where people do not dwell.
Malbim: A Ke'as lives in the Midbar. It eats fish. Each day it must go far to the rivers to trap fish 1 . So I dwell in Midbaros, separated from people, and I need to go covertly to settled places to seek my income.
Chulin 63a says that Shalach takes fish from the sea. That is a different species, mentioned in the previous verse. (PF)
What is "Kos Charavos"?
Rashi: Kos is a species of bird, like "v'Es ha'Kos v'Es ha'Shalach v'Es ha'Yanshuf" (Vayikra 11:17). Charavos are Midbaros.
Radak, Malbim: It is a bird that dwells in Charavos (ruins).
What is the comparison to "Kos Charavos"?
Radak: It has a lamenting voice.
Malbim: After the yoke of Galus lightened a little, and I was allowed to dwell in a settled place, they did not let me dwell in the city. I was like Kos Charavos, which dwells in ruins in front of the cities, separated from the city.
