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Abstract: Tara iti (New Zealand fairy tern, Sternula nereis davisae) are one of Aotearoa New Zealand’s most endangered birds, with decades of conservation effort focused on population monitoring, predator control, and habitat protection. This study examined fish species available to and consumed by tara iti through seine-net surveys (2021–2024) at Waipū and Mangawhai estuaries, supported by direct feeding observations and photography of feeding events. Forty-three fish species were identified across the two sites. While fish community composition differed significantly between estuaries, most variation occurred within sites. Waipū supported a greater diversity of small-bodied indicator species and juveniles of diadromous or estuarine-dependent taxa, whereas Mangawhai was dominated by juvenile flounder and gurnard. All indicator species represent suitable prey for tara iti and their chicks, highlighting the role of estuaries during the breeding season. However, sampling effort remains biased toward east coast estuaries and summer months, underscoring the need for broader temporal and spatial surveys.