Revelation 19:17

And I saw an angel standing in the sun; and he cried with a loud voice, saying to all the fowls that fly in the midst of heaven, Come and gather yourselves together unto the supper of the great God;

The heaven where the fowls fly is the atmosphere around the earth, and this use is distinct from Paradise, from the region of the sun, moon and stars, and from the church of God on earth.
The angel standing in the sun is Jesus Christ in heaven, reflecting no shadows, clothed in the attributes of Deity, shrouded in the glories of Deity, in the likeness of the infinite God.
The verse depicts the angel announcing the supper of the great God and summoning with a loud voice all the birds flying overhead to gather and eat the flesh and bodies of the wicked defeated in the final battle and conflict.
The scene belongs to the battle of Armageddon, in which Christ as King of kings leads the armies of heaven against the beast, the kings of the earth and their forces, the beast and false prophet are cast into the lake of fire, and the remaining enemies are slain.
The taking of the beast and the false prophet and casting them into the lake of fire leads into the binding of the dragon in the bottomless pit for a thousand years, the resurrection and final destruction of the wicked, and the final triumph and reign of Christ on earth.

The supper marks the end of Satan's rebellion, when the wicked are consumed at Christ's coming and God's judgment falls on those who opposed Him.
The summons means God will avenge His children on those who bore false witness against them, bruised them with fetters, burned them at the stake, caused them pain in the spirit of Satan, and compelled them to transgress the law God commanded all to obey.
As they caused suffering they will suffer, and they will perish under the judgment executed at Christ's coming.
The chapter's events will soon be fulfilled and form part of the last-day events shown as a living reality, describing the closing scenes of this earth's history now being lived, so the call to the birds is a prophetic scene of the coming end-time judgment.

The verse belongs to the truths of Revelation 18 and 19 about God's judgments that all must read and understand.
Those truths are testing truths for this time and the last call of mercy to be given more fully to the world, connected with the coming judgments on the wicked and the urgent warning that must be given before they fall.
God shows mercy by long forbearance, holding back His judgments while waiting for this message of warning to be sounded to all, because many have not yet heard it.
The nineteenth chapter holds messages that every minister as a watchman on the walls of Zion must discern and give with a certain trumpet sound, since failure brings eternal loss and leaves many souls quieted to sleep.

Christ is to be lifted up before men as the sinner's only hope of salvation, with the righteousness of Christ connected with the law constantly kept before the sinner, made the groundwork of every discourse, meditated upon, hung in memory, and uttered by the lips.
When He is kept before the people creature merit sinks into insignificance, and the more the eye looks upon Him and His life, lessons and perfection of character are studied, the more sinful and abhorrent sin appears.
By beholding, a person admires Him, becomes more attracted and charmed and more desirous to be like Jesus, until assimilated to His image with the mind of Christ, walking with God like Enoch with the mind full of thoughts of Jesus as the best friend.