What is "Kesus Agur"?
Rashi #1: Like Kesus (a kind of bird) and a crane 1 . Radak - the prefix Vov is omitted, like "Shemesh Yare'ach" (Chabakuk 3:11), "Reuven Shimon" (Shemos 1:2 and similar verses.
Rashi #2: Like a bird, that they grab it by its neck, and it chirps. Targum Yonasan (k'Sus d'Achid u'Menatzef) is like this. Radak - Menatzef is like Chazal said Sus she'Tzanaf (Bava Kama 18b), just the letters are reversed, like Kesev and Keves. Chizkiyah said, amidst my illness I will chirp like a bird, like a Choleh groans.
Radak: Sus is like "v'Sor v'Sis v'Agur" (Yirmeyah 8:7); there it is written 2 with a Yud. There, Targum Yonason is Korchiya. We find that Reish Lakish screamed like a Kruchiya (Kidushin 44a); Rashi there explained that it is a crane. The Targum of Agur is Senunisa, i.e. Senunis that Chazal mentioned. Rav Hai Gaon said that this is Arunda.
Malbim: These are migrating birds - "v'Sor v'Sis v'Agur Shamru Es Bo'anah" (Yirmeyah 8:7; they guard the times of their coming). They go at the beginning of winter, when they see wings of death spread over all the living, so they go to warm lands, so I go to my place.
In our texts, it is written with a Vov but pronounced with a Yud. (PF)
Why did he say "Dalu Einai la'Marom"?
Radak: Amidst the severity of my illness, I lifted my eyes to Kel, who is above, and asked Him to take me from my illness. Radak - here Dalu is lifting, like "Aromimcha Hashem Ki Dilisani" (Tehilim 30:2) and similar verses. Lifting eyes is to Hashem - "Elecha Nasasi Es Einai ha'Yoshvi ba'Shamayim" (Tehilim 123:1). Even though Hashem does not have a place, His great honor is in Shamayim.
Malbim: My eyes lifted to Shamayim, to my place above. My soul lifted its eyes when it saw people around me dying naturally and returning to the soul's place in Shamayim, like these birds migrate to the place of Tzaltzel of their wings.
Why did he say "Ehgeh ka'Yonah"?
Malbim: (On the one hand, I viewed myself like a migrating bird, ready to return to my place. On the other hand,) I am like a dove, which guards its nest and never leaves it. My soul saw that death comes to steal its nest. It cried like a dove
What is the meaning of "Ashkah Li"?
Rashi: This is like Ashkah Osi 1 [mi'Yado]. Hashem took me from the angel of death and was a guarantor for me.
Radak: Perhaps this is a command, even though the Ayin is not Chatuf 2 , rather, it is Ma'arich (pronounced normally, and not hastily). Also "Shamrah Nafshi" (Tehilim 86:2, is Ma'arich, even though it is a command). Ashkah refers to adding, like Chazal said (Bava Metzi'a 52a) Ashik l'Gavech v'Shavi l'Chorseich (overpay (if needed), for [clothing to cover] your body, but pay the proper value (but not more, for food) for your stomach. I told Hashem to add to my days, and give relief and serenity.
Malbim: [My soul cried, for] they want to steal my nest (uproot me from life).
Rashi: Also "Refa Na Lah" (Bamidbar 12:13) is like Refa Osah.
I.e. there is not Chataf Patach under it, and then it is pronounced hastily, like is normal when it is a command, e.g. "Aseh Lecha Tevas" (Bereishis 6:14). (PF)
What is the meaning of "Arveni"?
Rashi: He was a guarantor for me 1 . This is like "Arov Avdecha l'Tov" (Tehilim 119:122).
Radak: This is like "Arov Avdecha l'Tov" (Tehilim 119:122) - [give] relief and serenity.
Malbim: From those who want to steal my nest, and save me from death!
