aggressive Australian birds chroicocephalus novaehollandiae common gray and white grey and white gulls Larus novaehollandiae Noisy prolific resting river river's edge riverside sand scavengers screeching seagulls sepia silver gull standing wading waiting watching cascading chroicocephalus-novaehollandiae city colors colours cool cooling edge edges edging flow flowing fountain gray-and-white grey-and-white Larus-novaehollandiae levels light multi-level reflecting ripples rippling seabirds silver-gull splashing water waterbirds breeze feathered feathers huddled path pavement paving river's-edge ruffled ruffling wind anas-superciliosa aquatic-birds bank black-eye-stripe brown-duck color colour differences diversity ducks fauna fowl grass grassy grey-duck harmonious harmony lake lakeside non-threatening not-threatened Pacific-black-duck quiet relaxed relaxing shadows slope sunlight sunshine together waterfowl widespread wild-ducks wild-life