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 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 present in an ecosystem even if the bird is rarely seen. In the Pacific Northwest of the United States, a program called NatureMapping collects data by educating the public and having them pool their data in a citizen science application. Data can be collected