mrski
My Pet Shop, has large bins with different seed mixes. There are several mixes for finches, several for canaries, budgies, and on to larger birds.
I will pick the simplest mixes for my birds, because I don't like all the little coloured bits and what nots that are added to a lot of the fancier mixes. No one eats them, and it's just a waste.
I also buy bags of wild finch seeds, plain canary seed, red millet, oats and groats, and white millet.
To all this, I add some wheat, and Polish canola, and mix it all together for all of my birds.
All of my birds (from the tiniest Waxbills, up to Canaries and Budgies) do very well on this mixture, and the left overs are tossed outside for my herd of Sparrows.
In Spring, Summer, and Fall, I collect different wild seed heads and these are added to their diet as well.
I don't buy pellets (don't believe in them).
I feed a large variety of greens and some fruit. Hard boiled eggs, mixed with crushed freeze dried mealworms and spray millet crumbles.
To the species that enjoy live foods (a catagory into which your Cordons would fall), I offer small mealworms and flightless fruit flies, which they enjoy tremendously.
I would recommend offering some live foods, and some insect pate mixtures to your wild caught birds, along with seeds and a variety of veggies.
I think the more variety the better, offered in small amounts.
Good luck