Endangered prey and their at-risk predators
Gull-billed Terns, a Species of Special Concern, are efficient predators and can include endangered California Least Terns in their diet. (Photo: M. Sadowski; courtesy of Naval Base Coronado).
In nature, species can co-exist with their natural predators, as long as population sizes are in balance. However, when species are listed as endangered, threatened, or of conservation concern, the loss of even a few individuals can be a cause for concern.
Gull-billed Terns are much larger than endangered California Least Terns, and their diet includes invertebrates and prey from the sea surface and on land. Unfortunately, Gull-billed Terns also prey on California Least Tern chicks and adults, and they can devastate nesting colonies. However, Gull-billed Terns are also in peril and are listed as a Species of Conservation Concern by the USFWS. Re-establishing balance for successful management of such species is challenging and requires an ecosystem approach that will include research and monitoring of prey and predators.
GPS tags can also be used on the larger Gull-billed Terns to understand their foraging and wintering habitat. Future studies can provide insight on where our conservation efforts are most needed and what actions are effective, such as re-location of particular individuals, habitat restoration, or even habitat engineering to re-establish a natural balance that includes predators and their prey in sustainable numbers.
Both California Least Tern and Gull-Billed Tern populations are affected by widespread habitat loss, disturbance at their nesting beaches, predators that are not native to the area or that are at higher densities than would be found under natural conditions, and other factors, such as poor foraging conditions, pollution, and climate change.
The following video shows how efficiently Gull-billed Terns can hunt their prey, a California Least Tern chick in this case, despite the presence of its parent. (Video posted by anonymous contributor on YouTube; video shared with permission from Naval Base Coronado).
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