Ken Saladin :
Birds do n’t have a urinary bladder . Doing aside with that is one of the hallmark adaptations of birds for flight , as a urine - occupy bladder would weigh them down . They pass their " urine " as a white library paste , resembling toothpaste , mixed with feces , from a individual possibility visit a vent , rather than an anus — although some source , like the one I quote next , take a footling liberty with the term .
perverse to another answer already reach to this enquiry , one ornithology website speaks of the hiss ’ “ outer anal retentive opening , which is close by a strong sphincter muscle " ( known as thecloaca ) . From my observations of birds , I sense sure that is correct .
Among other such observance , I ’ve often watch over the dry land - snuggle gentle - foot boobies in the Galápagos Islands . When they ’re sitting on the nest and have to take a crap , they fend up , point their tail end end away from the sun , and let out a ashen pasty squirt of mixed feces and piss . As the sun crosses the sky , they present in a different direction hour after hour , like feather sundials , so the white guano make a address - like array around the center of the nest . I do n’t believe they could do this if they did n’t have mastery over an anal retentive ( cloacal ) sphincter .
I know also that many birds take a shit just before they take flight ( so do bats ) for lighten the body a small . In tree - nesting birds ( cup nest in branches , stick - nests of hawks and eagles , tree - hole nest of owls and woodpeckers ) , when the bird has to defecate , it stands up and hangs its tail end over the sharpness of the nest or outside the flange of the tree hole and LET go , rather than defecating in the nest . When seagulls and terns pack a somebody or a predator , they bulk large overhead and defecate abundantly on their enemy . These behaviors , too , mouth of a sphincter with voluntary control .
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