31 He told them another parable: “The kingdom of heaven is like a mustard seed, which a man (God) took and planted in his field. 32 Though it is the smallest of all seeds, yet when it grows, it is the largest of garden plants and becomes a tree, so that the birds come and perch in its branches.” Mt 13:31,32; Mk 4:30,31,32 (shade)
God the Father is the owner of the vineyard and Jesus is the seed Gal 3:16 who was planted in His field. This is referring to Jesus’ death which produced many believers Jn 12:24.
A seed produces a tree; Jesus produced the Kingdom of Heaven.
The birds would be those far off (have to fly to the tree), Gentiles who come to the Kingdom for shade/comfort=eternal life (the Jews are those who were near) Eph 2:11,12,13,17.