Silkie the "SHH" gene, called the ZPA Regulatory Sequence (ZRS). This causes ectopic "SHH" expression in the anterior of the developing limb bud, leading to increased tissue growth and digits. While the feet of the Silkie display polydactyly, the wings have the standard tridactyly (three digit) arrangement. The Japanese Silkie initially develops additional digits in the wing as an embryo, but these are lost prior to hatching. The genetic cause behind Silkie polydactyly differs from those that cause polydactyly in the Dorking chicken breed, which is due to ectopic "FGF4" expression in the AER, with ectopic "SHH" a secondary effect. The
Bird tracks in the field using a handheld palm pilot and GPS system that streamlines the collection process. This free program is called CyberTracker. In order to make sure that data is reliable, a tracker evaluation system has been put in place through the CyberTracker organization. Bird tracks Bird tracking provides a way to assess the habitat range and behavior of birds without ever seeing the bird. Bird tracking falls under the category of tracking and is related to animal tracking. A guide to bird tracking has been published. Bird tracking is a tool used by naturalists to assess what birds are