Isaiah 31

Like birds
כְּצִפֳּרִ֣ים (kə·ṣip·po·rîm)
Preposition-k | Noun - common plural
Strong's 6833: A little bird

hovering overhead,
עָפ֔וֹת (‘ā·p̄ō·wṯ)
Verb - Qal - Participle - feminine plural
Strong's 5774: To fly, to faint

so
כֵּ֗ן (kên)
Adverb
Strong's 3651: So -- thus

the LORD
יְהוָ֥ה (Yah·weh)
Noun - proper - masculine singular
Strong's 3068: LORD -- the proper name of the God of Israel

of Hosts
צְבָא֖וֹת (ṣə·ḇā·’ō·wṯ)
Noun - common plural
Strong's 6635: A mass of persons, reg, organized for, war, a campaign

will protect
יָגֵ֛ן (yā·ḡên)
Verb - Qal - Imperfect - third person masculine singular
Strong's 1598: To cover, surround, defend

Jerusalem.
יְרֽוּשָׁלִָ֑ם (yə·rū·šā·lim)
Noun - proper - feminine singular
Strong's 3389: Jerusalem -- probably 'foundation of peace', capital city of all Israel

He will shield it
גָּנ֥וֹן (gā·nō·wn)
Verb - Qal - Infinitive absolute
Strong's 1598: To cover, surround, defend

and deliver it;
וְהִצִּ֖יל (wə·hiṣ·ṣîl)
Conjunctive waw | Verb - Hifil - Conjunctive perfect - third person masculine singular
Strong's 5337: To strip, plunder, deliver oneself, be delivered, snatch away, deliver

He will pass over it
פָּסֹ֥חַ (pā·sō·aḥ)
Verb - Qal - Infinitive absolute
Strong's 6452: To hop, skip over, to hesitate, to limp, to dance

and preserve it.”
וְהִמְלִֽיט׃ (wə·him·lîṭ)
Conjunctive waw | Verb - Hifil - Conjunctive perfect - third person masculine singular
Strong's 4422: To be smooth, to escape, to release, rescue, to bring forth young, emit sparks

KJV As birds flying, so will the LORD of hosts defend Jerusalem; defending also he will deliver it; and passing over he will preserve it.

NIV Like birds hovering overhead, the LORD Almighty will shield Jerusalem; he will shield it and deliver it, he will ‘pass over’ it and will rescue it.”

BSB Like birds hovering overhead, so the LORD of Hosts will protect Jerusalem. He will shield it and deliver it; He will pass over it and preserve it.”

NASB Like flying birds so the LORD of armies will protect Jerusalem. He will protect and save it; He will pass over and rescue it.

BST As birds flying, so shall the Lord of hosts defend; he shall defend Jerusalem, and he shall rescue, and save and deliver.

Like birds hovering overhead, so the LORD of Hosts will protect Jerusalem: The word "hover" is the same word used to describe the motion of the Spirit "hovering over the water in creation" (Genesis 1:2), perhaps here is the turning point for the recreation motif. 
When a bird hovers, it produces wind and moves the dust around, perhaps what divides the waters from the waters and makes that holiest place when dry land appears. Also, this may be a reference that the horses of Egypt are flesh, not "wind." 

Birds hovering also represent protection, as they hover over their nest or their prey. The same Hebrew word for "hovering" (uwph) is used in Isaiah 6:2 to describe the seraphs; they were "hovering" rather than flying. Wings represent power (D&C 77:4).

The king of Assyria bragged that "the nations" who didn't receive protection Isaiah 13-23 (covering), were like an abandoned nest where he was able to reach and take the eggs, and there was no wing to wave (Isaiah 10:14). The difference is that in that nest, they were "eggs" and here we are going to see those eggs hatched. 

To the Israelites, the eagle's wings represented divine intervention, represent covering, and wind to scare the enemy and carrying them up or ascenion. When they were delivered from the Egyptians, the Lord described the process as being carried on an eagle's wings: 

You yourselves have seen what I did to Egypt, and how I carried you on eagles’ wings and brought you to myself. (Exodus 19:4 NIV)

The same is also portrayed in the song of Moses in Deut 32:11, where there is a process of ascension:
1. Stirr up her nest
2. Hover over the young
3. Spread the wings
4. Take them and carry them. 

We see how this applied to the end-time church of God in Revelation:

The woman was given the two wings of a great eagle, so that she might fly to the place prepared for her in the wilderness, where she would be taken care of for a time, times and half a time, out of the serpent’s reach. (Rev 12:14).

He will shield it and deliver it Shield it and deliver it comes together. The Hebrew word used for the shield is גָּנַן (ganan), which also translates as "defend." It also translates as "to cover" or "to surround," which are synonyms for "to atone." The same word is used in Isaiah 37 by the Lord saying he will defend the city of Jerusalem for the sake of his servant David:

"I will defend this city and save it, for my sake and for the sake of David my servant!" (Isaiah 37:35).

The star of David, is also called the "shield of David," perhaps a connection, as Jehovah defends or shields the city for the sake of David or Davidic covenant, thus the shield of David.

 The other reference to the same word, "ganan" also appears in parallel with deliverance in Isaiah 38:

And I will deliver you and this city from the hand of the king of Assyria. I will defend this city. (Isaiah 38:6). 

He will pass over and preserve it: The Holy Days are a shadow of things to come (Colossians 2:16). Here we have the end-time Passover, where the Lord will pass over his people and destroy their enemies, the End-time Assyrians. It will be again an end-time configuration of the feast the Lord gives to the children of Israel. This is why Jeremiah says:

Therefore, behold, the days come, saith the Lord, that it shall no more be said, The Lord liveth, that brought up the children of Israel out of the land of Egypt;

But, The Lord liveth, that brought up the children of Israel from the land of the north, and from all the lands whither he had driven them: and I will bring them again into their land that I gave unto their fathers. (Jeremiah 16:14-15). 

The word pass over is pā·sō·aḥ, and only appears a few times in the Bible, most of them in Exodus 12 (12:13,23,27). The "preserve" also translates as "rescue." It is by passing over Jerusalem and destroying the Assyrian army that the Lord will preserve Israel.  

Hovering
2 Above it stood the seraphims: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly. (Isaiah 6:2). 

Nest, Wings
As one reaches into a nest, so my hand reached for the wealth of the nations; as people gather abandoned eggs, so I gathered all the countries; not one flapped a wing, or opened its mouth to chirp. (Isaiah 10:14)

Hover & Eagle's wings
Now the earth was formless and void, and darkness was over the surface of the deep. And the Spirit of God was hovering over the surface of the waters. (Genesis 1:2).

Ye have seen what I did unto the Egyptians, and how I bare you on eagles' wings, and brought you unto myself. (Exodus 19:4 KJV).

As an eagle stirs up its nest, Hovers over its young, Spreading out its wings, taking them up, Carrying them on its wings, (Deuteronomy 32:11 KJV).

And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent. (Rev 12:14 KJV)

Deliver it
And the LORD shall help them, and deliver them: he shall deliver them from the wicked, and save them, because they trust in him.(Ps 37:40)

Passover פָּסַח (pacach)
And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and the plague shall not be upon you to destroy you, when I smite the land of Egypt. (Exodus 12:13)

For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you. (Exodus 12:23)

That ye shall say, It is the sacrifice of the LORD'S passover, who passed over the houses of the children of Israel in Egypt, when he smote the Egyptians, and delivered our houses. And the people bowed the head and worshipped. (Exodus 12:27). 

And I, the Lord, give unto them a promise, that the destroying angel shall pass by them, as the children of Israel, and not slay them. Amen. (D&C 89:21)

The Lord’s scourge shall pass over by night and by day, and the report thereof shall vex all people; yea, it shall not be stayed until the Lord come;For the indignation of the Lord is kindled against their abominations and all their wicked works.Nevertheless, Zion shall escape if she observe to do all things whatsoever I have commanded her. (D&C 97:23-25)

(31:5) Jehovah “guards” or defends his elect against Assyria’s assault in a new Passover. The words “by protecting it he will deliver it, by passing over it, preserve it” create word links to other instances of Jehovah’s delivering his people: “I will protect this city and save it, for my own sake and for the sake of my servant David” (Isaiah 37:35); “I will deliver you and this city out of the hand of the king of Assyria; I will protect this city” (Isaiah 38:6); “Those whose minds are steadfast, [O Jehovah,] you preserve in perfect peace, for in you they are secure” (Isaiah 26:3; cf. 1:8; 41:11-12; 51:22-23; 54:15-17). (Avraham Gilead)

passing over (פָּסוֹחַ) passing over. Alternatively, it may be interpreted as an expression of sparing. (Rashi)

The closing line of v.5 recalls for us the exodus allusion in v.3, also perhaps the awesome vision in 4:5. The God of the exodus will protect his people in Jerusalem as he protected them in the wilderness by the pillar of cloud and fire (4:5) and in Egypt itself at the Passover. The single quotation marks in the NIV around “pass over” suggest this allusion, and this term is usually applied to the Passover (Ex 12:13, 23, 27; Nu 9:4; Jos 5:11; 2Ch 30:18). Facing Sennacherib and his great hosts, the people of Jerusalem are as safe as were their forebears in Egypt on Passover night, for the God who is planning a great slaughter of her enemies will once again protect her. (Grogan, Rev. Geoffrey W.. Isaiah. The Expositor's Bible Commentary) (p. 413). Zondervan Academic. Kindle Edition).