Flock size and structure influence reproductive success in four species of flamingo in 540 captive populations worldwide.

As global wildlife populations continue to decline, the health and sustainability of ex situ populations in zoos and aquariums have become increasingly important. However, the majority of managed ex situ populations are not meeting sustainability criteria and are not viable in the long term. Historically, ex situ flamingo (Phoenicopteriformes) populations have shown low rates of reproductive success and improvements are needed for long-term viability. Both flock size and environmental suitability have previously been shown to be important determinants of ex situ flamingo reproductive success in a limited number of sites in some species. Here we combined current and historic globally shared zoological records for four of the six extant species of flamingo (Phoeniconaias minor, Phoenicopterus chilensis, Phoenicopterus roseus, and Phoenicopterus ruber) to analyze how flock size, structure, and climatic variables have influenced reproductive success in ex situ flamingo populations at 540 zoological institutions from 1990 to 2019. Flock size had a strong nonlinear relationship with reproductive success for all species, with flock sizes of 41-100 birds necessary to achieve ca. 50% probability of reproduction. Additionally, an even sex ratio and the introduction of new individuals to a flock both increased ex situ reproductive success in some cases, while climatic variables played a limited role. We demonstrate the conservation management potential from globally shared zoological data and provide species-specific management recommendations to increase the reproductive success of global ex situ flamingo populations: minimum flock sizes should be increased, and we encourage greater collaboration between individual institutions and regional associations in exchanging birds between flocks.