You can go to your local bait & tackle shop and get some worms ... put them in a blender ... with just a little water ... just enough to liquefy them ... then feed the chicks with an eyedropper ...
As often as it squawks for food when you approach. Don't forget the water. Hold a water-filled eye-dopper against the side of the beak so's it gets a taste. If it wants water, it'll try and get more. If it doesn't, it'll turn its head away. Sorry, if you know about this. Good Luck! PS Raw beef mince is OK too.