Jizz or giss is the overall impression or appearance of a bird garnered from such features as shape, posture, flying style or other habitual movements, size and colouration combined with voice, habitat and location. The concept was popularised in birdwatching, but is so useful that it has since been adopted increasingly widely by field biologists in referring to the impression of the general characteristics of other animals.[1][2][3] It similarly appears in such fields of observational biology as microscopy.[4] Ecologists and botanists may speak of "habitat jizz" or the jizz of a plant.[5]
Sean Dooley described jizz as "the indefinable quality of a particular species, the 'vibe' it gives off" and notes that although it is "dismissed by many as some kind of birding alchemy, there is some physical basis to the idea of jizz."[6]
Experienced birders can often make reliable identifications in the field at a glance by using jizz. Often jizz is useful for identifying to the family or genus level, rather than the species level, as in: "It definitely had the jizz of a thrush, but I couldn't see what kind."