The survival and reproductive success of shorebirds is negatively affected by factors such as habitat loss and degradation, predation, and human disturbance. Disturbance from humans and avian predators can also affect the distribution and behaviour of non-breeding birds. However, the influence of these factors can be site- and species-specific. Therefore, the objective of this thesis was to determine the key factors that were affecting the nest success, distributions, and behaviour of birds at the Ashley-Rakahuri Saltwater Creek River Estuary, New Zealand. Firstly, I monitored the nests of seven shorebird species at the Ashley Estuary from 2022-2024. Nest success varied between species and years, but black-backed gulls (Larus dominicanus) had the highest nest success, while black-fronted terns (Chlidonis albostriatus) were the least successful. Predation and flooding were the two main causes of nest failure. I also evaluated the effect of habitat variables on banded dotterel (Charadrius bicinctus) and black-backed gull nest success. Black-backed gull nest outcomes were not affected by the measured habitat features, but earlier nests may have been more successful. Banded dotterel nests were more successful in the 2022/23 breeding season, mainly due to increased cat (Felis catus) predation in 2023/24. Successful banded dotterel nests were also closer to water on average than unsuccessful nests. Next, I used scan sampling to study the distribution and behaviour of estuarine birds in response to disturbance by humans and by a native avian predator, the Australasian harrier (Circus approximans). In response to human disturbance, pooled birds [all species except passerines and kingfishers (Todiramphus sanctus)] and waterfowl decreased in the disturbed area but began to return within 10 minutes after disturbance. Shorebirds were always more common in the undisturbed area, irrespective of the stage of human disturbance. Following harrier disturbance, pooled birds and waterfowl were less abundant in the western area of the estuary, while shorebird numbers increased overall regardless of the area, likely due to increased flocking behaviour. In addition to their distributions, bird behaviours may also have been affected by human disturbance. For example, the proportion of birds that were sleeping and preening in sectors bordering the disturbed area decreased during disturbance. Finally, I measured the FIDs and landing distances of estuarine birds in response to approaches by a single pedestrian. There were interspecific differences in FIDs, landing distances, and the method of fleeing used. Both FIDs and landing distances were highest for bar-tailed godwits (Limosa lapponica) and lowest for wrybills (Anarhynchus frontalis). Birds with longer FIDs generally also had longer landing distances, and FIDs and landing distances were typically longer in individuals that fled by flying, rather than walking. Based on the FIDs I measured, banded dotterels would require 66 m setback distances to minimise the effects of pedestrian disturbance, while pied stilts (Himantopus leucocephalus) would require 97 m setback distances. The results of this thesis add to existing knowledge around shorebird nest success and the effects of disturbance on New Zealand estuarine birds. My findings may be useful when developing future management outcomes for birds at the Ashley Estuary and similar sites throughout New Zealand, helping to protect our threatened shorebird species.