Jess (falconry) the bird, but the width is proportional to leg-length. Traditional jesses are made from a single length of leather, and slits are placed strategically along the jess to allow it to be looped through itself and around the ankle of the bird so that it fits comfortably but securely about and just above what would be the bird's ankle. With Aylmeri jesses, as created by Major Guy Aylmeri, the end of the jess is instead looped through itself repeatedly to form a "button", or knob at one end. The thin, pliable end of the jess is then threaded through an
The Macmillan Field Guides to Bird Identification geographical area of coverage are included; instead only groups of species which the authors regarded as difficult to identify are covered. Each such group is given a chapter, where identification is covered discurively rather than in the abbreviated form more usually used in a field guide. The publication of the first volume (covering Britain and Ireland) was the first time that this approach had been used in a European guide The first volume is widely credited as having a major influence on improving the identification skills of birders in Britain during the 1990s. The Macmillan Field Guides to Bird Identification