river martin river form distinctive subfamily swallow martin bird family species african river martin found white eyed river martin known site thailand medium sized largely black light flight feed insects caught air appear terrestrial frequently walking white eyed african species nest holes sandy ridges rivers breeding locations habits asian bird unknown african river martin discovered 19th century thought roller later authors placed family study anatomy revealed species closest possessed number distinctive features robust legs feet stout bill indicated placed separate subfamily river martin species usually considered belong single genus having number structural similarities proposed white eyed river martin placed separate genus african river martin restricted distribution appears locally numerous true status fully investigated white eyed river martin discovered recently known specimens evidence modern seen species wild breeding grounds unknown extinct possible sighting reported taxonomy specimen african river martin formally described german zoologist initially identified member swallow martin family placed later authors separate family following study anatomy species determined closely related sufficiently different placed separate subfamily genus comes ancient greek prefix pseudo false swallow reflecting true years african river martin sole member genus subfamily discovery white eyed river martin thai authorities follow placing species separate genus significant differences african species remains member subfamily genetic studies confirmed river form distinct clade typical subfamily river ways intermediate typical stout bills large feet relatively strong legs unusual aerial large vocal organ different structure extent differences wide geographical separation suggest populations group species diverged main swallow lineage early evolutionary history primitive like early nest adopted nest holes mud nests description species medium sized mainly black unlikely confused respective ranges adults species large blue heads green body plumage brown wings sexes similar plumage white eyed elongated outer tail feathers whitish white eye eye ring yellow bill african red eye ring bill lacks contrasting patch tail juveniles species similar adults brown heads young white lack long tail adults african river martin cheer cheer cheer flying flocks vocal migration giving harsh like calls appears courtship song calls described white eyed river martin distribution habitat members subfamily geographically separate ranges african river martin breeds rivers migratory coastal savannah southern recently discovered nest beach ridges grassland coastal areas white eyed river martin known site lake thailand seen months november february migratory breeding grounds habitat unknown river valleys south western china possibilities doubts cast actually migratory african species breeding habitat consists forested rivers islands sandy shores breeding nesting grounds white eyed river martin unknown breeding habitat resembles relative likely forested valleys large rivers provide islands nesting woodland birds catch insect prey african river martin uses coastal savannah winter habitat based known site non breeding habitat white eyed assumed vicinity open fresh water feeding reed beds night time behaviour breeding behaviour known african river martin nests large colonies birds december april river levels low pair long tunnel exposed pocket end tunnel twigs leaves serve nest white eggs laid chasing flight displays walk ground displays ground function uncertain rarely breeding season assumed breeding habits white eyed species resemble african species distinctive differences foot toe morphology suggest use nesting african river martin feeds flocks river forest far water eats insects mainly taking winged ants flight strong fast interspersed birds regularly perch wires roofs white eyed river martin feeds insects including beetles caught wing given size unusual mouth structure larger insects species described graceful flight like african relative appears reluctant use behaviour unusual toe shape fact mud found toes specimens suggests species relatively terrestrial winter barn suggested given unusually large eyes species nocturnal factor highly cryptic partly explain distinctive species remained long fact specimens supposedly collected night reed beds possible birds actually caught feeding dawn dusk capable nocturnal behaviour depending season local circumstances status white eyed river martin seen thailand definitely unconfirmed sightings thailand classified critically endangered iucn designation means species numbers decreased decrease generations species extinct iucn extensive targeted surveys conducted despite legal protection appendix convention international trade endangered species wild fauna flora cites agreement captured locals sale food release devout following discovery reported caught sold director unable alive captivity small population non viable factor reduces chances discovering white eyed martin drastic decline numbers known site hundreds thousands reported maximum counts winter certain represents real decline shift site response persecution potential causes species decline include disturbance sand bars construction dams flood area upstream alter downstream increasing conversion habitat agriculture preferring plantations despite searching white eyed river martin found nearby large swallow declared non hunting area effort protect species surveys find martin unsuccessful past surveys include survey northern thailand survey rivers northern possible sighting reported total population size african river martin unknown late 1980s appeared common local large numbers seen migration particularly poorly known unclear relationship birds breeding breeding coastal areas flock birds seen mixed flock bee estimated birds lack detailed information species classed iucn 1950s species caught eaten large quantities local population practice increasing breeding colonies river liable flooding thousands birds breeding east recently
River martin