E Glossary of bird terms

eggs of: ostrich, emu, kiwi , chicken



ear-coverts
small covert feathers located behind bird s eye, in 1 4 rows, cover ear opening (the ear of bird has no external features) , may aid in acuity of bird hearing.
egg



also defined herewith: eggshell, yolk, albumen; chalaza. organic vessel containing zygote, in birds develop until hatching. eggs oval in shape, , have base white colour predominant calcium carbonate makeup of outer shell, called eggshell, though passerine birds may have eggs of other colours, such through deposition of biliverdin , zinc chelate, give green or blue ground colour, , protoporphyrin produces reds , browns. viable bird egg (as opposed non-viable egg: see addled eggs) consists of number of structures. eggshell 95–97% calcium carbonate crystals, @ least in chickens, stabilized protein matrix, without crystalline structure brittle keep form; organic matrix thought have role in deposition of calcium during mineralization process. structure , composition of avian eggshell serves protect egg against damage , microbial contamination, prevention of desiccation, regulation of gas , water exchange growing embryo, , provides calcium embryogenesis. inside eggshell 2 shell membranes (inner , outer), , @ center yolk—a spherical structure, shade of yellow, fertilized gamete attaches , embryonic bird uses sustenance grows. yolk suspended in albumen (also called egg white or glair / glaire) 1 or 2 spiral bands of tissue called chalazae. albumen protects yolk , provides additional nutrition embryo s growth, though made of approximately 90% water in birds. prior fertilization, yolk single cell ovum or egg cell; 1 of few single cells can seen naked eye.
egg incubation



also, brooding. general care of unhatched eggs parent birds (more females birds of both sexes), temperature regulation through sitting on them, crouching or squatting on them, covering them wings, providing shade, wetting eggs , related behaviours. target temperature of species 37 °c (99 °f) 38 °c (100 °f). in monogamous species incubation duties shared, whereas in polygamous species 1 parent wholly responsible incubation. warmth parents passes eggs through brood patches—areas of bare skin on abdomen or breast of incubating birds. incubation can energetically demanding process; adult albatrosses, instance, lose as 83 grams (2.9 oz) of body weight per day of incubation.


a senegal parrot chick @ 2 weeks after hatching. egg tooth near tip of beak on upper mandible.



egg tooth



a small, sharp, calcified projection on beak full-term chicks of bird species have, use chip way out of egg. commonly known egg tooth, white spike near tip of upper mandible, though species have 1 near tip of lower mandible instead, , few species have 1 on each mandible. despite name, projection not actual tooth (as similarly-named projections of reptiles are); instead, part of integumentary system, claws , scales. hatching chick first uses egg tooth break membrane around air chamber @ wide end of egg. pecks @ eggshell while turning within egg, (over period of hours or days) creating series of small circular fractures in shell. once has breached egg s surface, chick continues chip @ until has made large hole. weakened egg shatters under pressure of bird s movements. egg tooth critical successful escape egg chicks of species perish unhatched if fail develop one.
emargination



a pronounced narrowing @ variable distance along feather edges @ outermost primaries of large soaring birds, particularly raptors. whether these narrowings called notches or emarginations depends on degree of slope. emargination gradual change, , can found on either side of feather. notch abrupt change, , found on wider trailing edge of remige. presence of notches , emarginations creates gaps @ wingtip; air forced through these gaps, increasing generation of lift.
eye-ring



also defined herewith: orbital ring. visible ring of feathers around bird s eye; eye-ring paler surrounding feathers. contrast, orbital ring bare skin ringing eye. in species, such little ringed plover, orbital ring may quite conspicuous.
eyestripe
also eye line / eyeline. visible stripe on feathers of bird s head, darker surrounding feathers, running through eye region. compare supercilium.