| Aberrant Abnormal or unusual | Crown Upper part of head |
| Accidental Vagrant | Crown-stripe Distinct line from forehead along centre of crown |
| Adult Mature, Capable of breeding | Cryptic Hidden - having protective colouring and/ or behaviour |
| Aerial Making use of the open sky | Culmen Ridge on upper mandible of bill |
| Allopatric Relating to two or more related species whose range do not overlap | Cursorial Ground running |
| Altitudinal migrant Moving between high mountains and lower foothills | Deciduous Trees that shed their leaves annually |
| Altricial Blind and helpless when hatched | Decurved Curving downwards |
| Apical Outer extremities, particularly of the tail | Diagnostic Sufficient to identify a species or subspecies |
| Aquatic Living on or in water | Dimorphic Having two forms of plumage |
| Arboreal Living in trees | Distal Terminal or the outer end |
| Ashy Greyish Colour | Diurnal Active during daytime |
| Axillaries Underwing feathers at the base of the wings, forming ‘armpits’ | Down Small soft feathers close to body of chicks |
| Back Loosely applied to the mantle scapulars and rump | Drake Male duck |
| Banyan Type of fig tree | Drumming Rhythmic territorial hammering on trees by woodpeckers |
| Barring ‘Sideway’ lines such as on tail or breast | Duars Forested areas south of eastern Himalayas |
| Basal Innermost extremities, particularly of the tail or bill | Ear-coverts Feathers covering the ear opening. Often distinctly coloured |
| Bheel Shallow lake or wetland | Ear tufts Feathers protruding near ears |
| Biosphere The part of earth that is inhabited by life | Echolocate Navigate by sound |
| Biotope Area of uniform environment, flora and fauna | Eclipse Plumage New dull plumage after breeding season, especially in ducks |
| Bristles Sensory feathers near beak | Endemic Indigenous and confined to a place |
| Brood Young hatched from a single clutch | Endangered Species facing high risk of extinction |
| Brood Parasitism Depositing of eggs by one species in the nest of an another | Eurasian Of both Europe and Asia |
| Buff Yellowish white with a hint of pale brown | Evergreen Forests that always have leaves |
| Bund Man-made mud embankment | Eye-ring Contrasting ring around the eye |
| Canopy Leafy foliage of treetops | Eye-stripe Stripe through eye |
| Cap Upper part of head | Extinct No longer in existence |
| Carpal Bend of a closed wing, sometimes called shoulder | Extirpated Locally extinct |
| Casque Growth above bill of hornbills | Extralimital Not existing in the region |
| Cere Patch of bare skin on upper base of bill of raptors | Facial Disc Heart shaped arrangement of feathers as in some owls and harriers |
| Cheek Term loosely applied to sides of head, below the eye or on ear coverts | Fallow Cultivated land after cultivation and before ploughing |
| Chevrons V-shaped contrasting marks on wings or bands across breast | Family Specified group of genera |
| Cinnamon Light yellowish-brown colour | Forage Search for food |
| Clutch Complete set of eggs laid by a single female | Ferruginous Rusty-brown colour |
| Collar Distinctive band of colour that encircles or partly encircles the neck | Feral Escaped, and living and breeding in the wild |
| Colonial Roosting or nesting in groups | Filoplume Hair-like feathers like in breeding egrets |
| Confiding Not shy | Flank Side of body |
| Commensal Living together with man for mutual benefit | Fledged Having just acquired feathers and ready to leave nest |
| Coverts Small feathers on wings and base of tail | Fledglings Young birds which have just acquired feathers |
| Covey Small group of partridges and allied species | Flight feathers Primary and secondary wing feathers |
| Crepuscular Active at dusk (twilight) and dawn | Flushed When disturbed into flight at close quarters |
| Crest Extended feathers on head | Foreneck The lower throat |
| Crop Pouch-like enlargement of gullet in some birds where food is partially digested | Form Sub-species |
| Frons Forehead |
