Leviticus 1:14

And if his oblation before the Lord be of birds he shall bring his oblation from the turtle doves or the young Of pigeons; but of the turtle doves he shall bring the largest, and of the pigeons the young ones.

turtledoves fully grown, not young ones.

young of pigeons Scripture does not simply say “pigeons”, to exclude the fully-grown.

OF TURTLEDOVES OR OF YOUNG PIGEONS. Scripture chose these two species [of birds] because they are accessible and can be more easily caught than other [birds], just as our Rabbis have mentioned with reference to any of the sheep, and any of the goats, that [Scripture chose these species so that] a person should be able to bring an offering from those animals that feed at his crib, and should not have to take his weapons, quiver and bow, to go out on the hunt to bring it., Verse 3. He chose grown-up turtledoves 3:2). because they abstain [from pairing with strangers] and attach themselves only to their mates, and once they lose their companions they never associate with others. So Israel cleave to the Eternal their G-d, and never attach themselves to another deity, Pigeons, on the other hand, are very jealous and as a result of their jealousy they part [from their previous mates] and take on other mates. Therefore He chose them [as offerings] only when they are young, before their mating begins, for as long as the pigeon is young it is attached with greater love to the nest where it is reared than are all other fowls. Our Rabbis have mentioned that if a person touches the nest of all other fowls to take therefrom the young ones or the eggs, they leave it and never nest therein again, but the pigeon never abandons it under any condition. And so is [the people of] Israel. They will never exchange their Creator and His Torah, but “either Jews or nailed to the stake.” He did not choose cocks [as offerings although they are readily accessible] because of their inclination to lewdness.
Now the Rabbi [Moshe ben Maimon] wrote in the Moreh Nebuchim that the reason for choosing grown-up turtledoves and young pigeons as offerings is that these are the best of their species, since old pigeons are less tasty. But this is not true, for young pigeons are almost inedible as a result of their excessive moistness. If, however, we are to take into consideration their natural tendencies as far as eating them is concerned, it is possible that they were chosen for their special qualities; for turtledoves have a propensity to sharpening of the mind, and young pigeons have a propensity to benefit greatly those who are not fully-matured physically, such as youths in the intermediate stage between boyhood and maturity, and the like.