So these are actually useful. If you use it to attack dodos, lystros, fish and other small creatures it kills them and they glow. When they glow and you harvest them you get prime meat from land animals and prime fish from fish.
When set to "Hunt & Retrieve" it will bring you dodos or fish and the dodos will give raw prime or a few of it. And fish will give raw prime fish meat. You'll know cause the corpse will glow yellow as the icthyornis is bringing it to you!