Bill Color in 1st Cycle Ring-billeds

Although bill coloration in 1st cycle Ring-billeds is generally described as being pink with a black tip, this pink soon becomes a shorbert orange and a yellowish-green in SY birds. The effect is quite noticable in their first spring:

1st Cycle Ring-billeds all photographed on 21 April 2014. Hammond, Indiana.

Bird #1 is what HY birds typically look like, and bird #4 looks more like a second cycle's bill.

It makes perfect sense that bill color would begin transitioning to a yellow at this time of the year, when hormonal levels peak.