Mariana Crow -- Sasha Shebalin

Campbell-Smith, Jenifer. “Mariana Crow.” The Corvid Blog, http://coyot.es/thecorvidblog/.

Mariana Crow (Corvus kubaryi)

About the species

The Mariana Crow or better known locally by indigenous people as Aga is a bird species in the same family as ravens, magpies, and jays. This species looks similar to the common crow we know in California. It is has a black body with a green tint. They are shy animals which were at one point respected as a positive symbol and were said to have the ability to converse with their owner; however in more recent times they’re seen as a bad omen.

This species is an omnivore and an opportunistic feeder. It enjoys eating insects, lizards, bird eggs, hermit crabs, fruits, and seeds. This helped keep those populations in check, but now we are losing a piece of the food web.

Where is it found? How many are left?

Aga are an endemic species to the islands of Guam and Rota. Although they have been noted to use a variety of forested habitats like strand, ravine, agricultural or secondary forests they prefer limestone forests. Their nests have only been recorded in native tree species.

In 1976, Aga were considered to be a common, widely distributed bird on Rota island. In 1981 it was reported there were only 350 birds, then fewer than 40 in 1995, and 7 in 1999 (iucnredlist.org). The last known native Aga was believed to have disappeared around 2002.

USFWS. “Critical Habitat, Mariana Crow.” http://www.botany.hawaii.edu/basch/uhnpscesu/htms/parkrota/fig9.htm.

Endangerment Rating

According to the U.S. Fish and Wildlife service’s recovery plan for the Aga the species was listed on September 28, 1990. The listing of endangerment they’ve assigned to the Mariana crow is 5C. This is on a scale where 1C is the highest and 18 is the lowest. The “C” notes its potential conflict with human activities.  

Center for Biological Diversity. “Mariana Crow.” Endangered Bird Trends, http://www.esasuccess.org/2016/far_pacific.shtml/.

Threats to Survival

There are a lot of factors affecting the Mariana crows success. As mentioned before the Aga only nests in native tree species and so habitat loss is affecting their ability to repopulate. Native trees are also where they forage for food and so the Aga are being affected by nutritional deficiencies as well. Human persecution and contaminants are also playing a role. Introduction of diseases and species such as cats, rats, black drongos, monitor lizards, and brown treesnakes have caused Mariana Crow populations to dwindle.

Rodgers, Halder. “Brown Treesnake.” Brown Treesnake, http://www.macroevolution.net/brown-tree-snake.html.

Recovery Plan

The recovery plan for the Aga has identified key steps that need to be taken in order to ensure conservation and recovery for the species. First, scientists must identify recovery zones. These zones are chosen according to the amount of current Aga habitats in the area. Areas with larger established crow populations mean the easier it will be to help them recover. This requires research into the population status and limiting factors. Meaning that they will need a data center, as well as surveying and monitoring equipment. Their second focus is on the brown treesnake. This species preys on the crows in their nesting habitats and has been stated to be the root cause of their decline. This means that research and reduction actions have to be taken on this species as well. Their starting point is to search ports, cargo areas, and other potential breeding grounds.

Weiser, Emily. “Adult Mariana Crow.” Without intervention, Mariana Crow to Become Extinct in 75 Years, https://www.washington.edu/news/2010/12/20/without-intervention-mariana-crow-to-become-extinct-in-75-years-2/l.

How to Help

Although I was unable to find an organization dedicated to the protection of Mariana Crows specifically, you can make donations to organizations that support the protection of bird species and the eradication of invasive species. Some recommendations are Pacific Islands Fish and Wildlife Service and Institute for Wildlife Studies. You can also educate others to raise awareness by posting to social media. Lastly, make sure to check all items you are bringing into other territories to prevent the spread of disease or invasive species.

National Research Council. “Preservation of the Mariana Crow.” 
https://www.nap.edu/catalog/5372/the-scientific-bases-for-preservation-of-the-mariana-crow.

Check Out These Sites for More Information

Recovery Plan: https://ecos.fws.gov/docs/recovery_plan/060111.pdf

US Fish +Wildlife Service: https://www.fws.gov/pacificislands/fauna/marianacrow.html

Red List of Threatened Species: http://www.iucnredlist.org/details/22705959/0

Citations

United States, Congress, Aguon, Celestino, et al. “Draft revised recovery plan for the Aga or Mariana crow (Corvus kubaryi).” Draft revised recovery plan for the Aga or Mariana crow (Corvus kubaryi), U.S. Fish and Wildlife Service, 2005, pp. 1–147.

Birdlife International. “Corvus kubaryi .” Corvus kubaryi (Guam Crow, Mariana Crow), International Union for Conservation of Nature and Natural Resources, 2016, www.iucnredlist.org/details/22705959/0.

US Fish & Wildlife Service. “Endangered Species in the Pacific Islands.” Pacific Islands Fish And Wildlife Services, US Fish and Wildlife Service, 20 Sept. 2012.