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Mariana Crow Rear and Release

Two Mariana crows on a branch

  • Scientific Name:  Corvus kubaryi
    Chamorro Name: Åga
    Common Name: Mariana Crow

    Åga in the News

    In the far western corner of the Pacific Ocean, the limestone forests on the islands of Guam and Rota are home to a species of crow found nowhere else on earth. But over the last 60 years, the Mariana crow - called the Åga in the native Chamorro language - has disappeared from the island of Guam, and is rapidly declining on Rota.

    Today, there are only about 175 Åga left in the world. But researchers and scientists from the University of Washington, San Diego Zoo Global, the U. S. Fish and Wildlife Service, and the Commonwealth of Northern Mariana Islands Department of Lands and Natural Resources are working to ensure that the birds have a future.

    The Åga was driven to extinction on Guam by the brown tree snake (Boiga irregularis) - an invasive predator that hitched a ride on military vessels. The brown tree snake has decimated most of the endemic bird population on Guam since it arrived there in the 1950′s. So far the brown tree snake has been kept out of neighboring Rota and the reasons for the birds’ decline there are less clear.

    Habitat and Range

    The Åga is a small corvid with a glossy green-black head and blue-black body.  Åga can only be found of the island of  Rota, a 33-square-mile island located about 3,700 miles west of Hawaii. There, the birds live in a variety of habitats across the island, but they only nest in the native limestone forests.

    Diet and Life Cycle

    The Åga is an opportunistic omnivore - meaning it will eat just about anything it can get its beak on. This includes lizards, grasshoppers, crickets, praying mantis, earwigs, and hermit crabs. The birds also forage on foliage, fruits, seeds, and buds.

    Åga lay 1 - 4 eggs at a time and both parents help to hatch and raise the chicks, even caring for the juvenile birds for up to a year after they fledged. Åga are slow to mature and  an take up to three years before they begin to breed successfully.

    Threats to the Species

    Over the past three generations (about 22 years), the population of Åga has fallen by over 80% and the species is projected to go extinct in less than 75 years. Predation by feral cats, nest disturbance by humans, nest loss from typhoons, habitat degradation, inbreeding and disease are all considered threats to the birds.  

    Reason for Hope

    Thanks to funding from the U.S. Fish and Wildlife Service through the CNMI Department of Lands and Natural Resources the University of Washington has been studying the Åga since 2005. Their work on nest monitoring, banding and re-sighting birds, pair surveys, disease investigation, and community outreach has been vital to our understanding of the Åga and provided the information needed to move forward in conservation efforts.

    In 2016, researchers began collecting eggs from wild Åga nests to be reared in captivity at a facility run by the San Diego Zoo Global. The birds are raised past the critical period of highest mortality, and then released.  This has the potential to greatly increase reproductive output because the wild Åga pairs will have the opportunity to lay another set of eggs.  So, in effect, they will have two broods in one year!  

     

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