At least 12,000 pelicans were in their final breeding stages in the Gayini wetlands after setting up inland six months ago.

Another large colony in the Lachlan Valley had also been observed.

Michele Groat from the Commonwealth Environmental Water Office said the full dams, lakes and rivers favoured the large birds.

"Pelicans like to breed in large colonies and nest on ground surrounded by water to protect their chicks from predators," Ms Groat said.

"Environmental water holders, scientists, water managers and the Nari Nari Tribal Council worked together to keep water levels stable at the breeding sites to protect the birds as much as possible.

"If water-levels got too high many chicks would have drowned and if water levels got too low the nests would have been exposed to predators like pigs and foxes."

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Ms Groat said it was important nests were located near a ready supply of food given it usually took four months for chicks to become totally independent.

She also said pelicans were big eaters and that adults could consume nearly two kilos of fish, tadpoles, crustaceans, turtles and even other birds per day.

"An additional benefit of having two large pelican breeding events in the area was that they are very effective at reducing local carp numbers," Ms Groat added.

NSW Department of Planning and Environment scientists applied leg bands to around 300 juvenile birds from both the Murrumbidgee and Lachlan colonies.

Scientists were confident the bands would provide more information on their movements and survival needs.

Despite the successful breeding season, Ms Groat said there was still lots to learn about the large bird, like how tens of thousands were able to navigate to the same breeding area when conditions were right.

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