Opalines are the newest mutation of peachface lovebird, first appearing in 1997.  The easiest areas to examine to know if the babies are opaline are the rump & head areas.  The earliest you would be able to tell would be 10-14 days.  It is easier said than done, but be patient.  At around 10 days the Opaline babies will start getting an unusual down.  The down on opaline babies is very thick which will generally set them apart from other normal chicks.  The green series opalines will get a very yellow down.  The blue series are a little more difficult to tell, but again, will have the thicker down.  As the feathers of an opaline start to emerge if you have an opaline you will see that the rump color is abnormal & closely matches the body color rather than the typical turquoise rump (for non-dark/violet factored birds).  The rear of the head is another indiction.  On a green series bird the red face color will extend further back on to the "neck" area of the bird.  In the blue series bird this area would be white rather than red.

Kera Groves