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Why is the CA Least Tern Endangered

        The number ONE threat to CA Least Tern is Sand Dredging. Sand Dredging is removing silt and other materials from the bottom of the ocean and from the shore of the ocean to use in development (What is Sand Dredging? 2017). In the U.S. sand mines cause erosion, water, and air pollution, and habitat loss (Bieser, 2015). In San Francisco an average of 3-6 million cubic yards of sediments are dredged per year (San Francisco Bay Long Term Management Strategy for Dredging, 2017). There are also many regulations on sand dredging but bribes are given to create wider and deeper mines illegally (Bieser, 2015).

         The California Coastal Commission has concluded that the CEMEX Lapis Plant dredges an estimate of 200,000 to 300,000 cubic yards of sand a year (Rogers, 2017). Sand dredging is an incredibly big industry; each CEMEX bag sells for $4.70 and is used for many things including filling golf courses (Rogers, 2017). The State Lands Commission, which is an agency that regulates offshore oil drilling in state waters, contacted CEMEX demanding that the company either start paying for the damage it’s created or shut down (Rogers, 2017). The company refused and ever since has been contributing to the amount of erosion and destruction on the nearby beaches (Rogers, 2017). CEMEX has six major mining plants along the coast of Monterey Bay; they used a technique called “drag lining” which includes scrapping and dragging sand from the shores with large metal spoons and is incredibly disruptive. In an attempt to be more environmentally friendly; the company switched to a technique where they pump sand from the lagoon (otherwise known as a wetland) which is primal CA Least Tern habitat (Rogers, 2017).

       The construction of the Pacific Coast Highway brought most of the threats to the CA Least Tern population and the California coast (California Least Tern). Many of the threats fall under HIPPCO which stands for; habitat destruction, invasive species, population growth (humans), climate change, and over-consumption.

Other socio-economic threats to the California Least Tern include:

  • Poaching for feathers (California Least Tern)

  • Beach development like beach houses and restaurants (California Least Tern, 2006)

  • Tourist activities cause humans to step on nests or water sports that disturb the CA least tern prey (California Least Tern, 2006)

  • Pollution including noise pollution from construction sites, pollution of materials, and pollution of the air (California Least Tern, 2006)

  • Destruction of wetlands for:

    • Commercial development, for example beach houses, restaurants, and parks (European Environment Agency, 2010)

    • Tourist activities, for example bird watching, photography, swimming, fishing, and enjoying the landscape (Chandrasekhar, 2013)

    • Agriculture uses such as fertile soil, food, clean water, and cycling of nutrients are gathered through wetlands (Department of the Environment, 2016)

    • Dams to harvest water

SAND DREDGING IS THE NUMBER ONE THREAT

Are Your Life Choices Contributing to the Death of California Least Tern?

Wetlands are the California Least Tern main source of food, the bird preys on small fish. Their habitat ranges from the Pacific Coast of California to Baja California (California Least Tern, 2016). With the destruction of wetlands increasing, the CA Least Tern population will have trouble finding prey. Extinction rates will increase (Ecosystem accounting and the cost of biodiversity losses, 2010). And another major important socioeconomic threat is Climate change (Threats to Wetlands, 2017). Climate change effects seabirds in many ways, from increase in population size putting a strain on the need for more and more resources; this means more sand dredging and more destruction of habitat (Safina, 2014). Climate change also affects the temperature and levels of salinity in the ocean; climate change is also putting more carbon dioxide in the ocean turning the waters more acidic. This is dangerous to the birds because some of their pray will not be able to survive in waters that are incredibly acidic, including some species like planktonic animals, corals, and shellfish (Safina, 2014). Colder seas are more productive because the cold winds in the ocean mix up the nutrients at the upper levels where plankton grows; and cool water holds more oxygen. Many seabirds take a while to adapt to the new ocean changes and a species like the CA Least Tern may not have the time to adapt in order to survive (Safina, 2014).

Overall, human activity in the bird's lovely ecosystem is the main cause for the decrease in the California Least Tern's population. The disturbance that people are causing in beaches, and taking away their food resources is a big issue for the bird. Some of the threats were controlled but not removed, so the tern is not totally able to reproduce more and recover, due to all the disturbance that is happening in their habitat, which should be a peaceful and quiet place. 

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Unfortunately, there is more... 

Image Courtesy of Pearson Scott Foresman

Wetland Destruction

Contaminants and Loss of Prey Species

       Contaminants, such as mercury and lead that are disposed on water, usually by industries, can directly kill this defenseless birds. These chemicals also kill their prey items, decreasing their amount of the so needed food.

       California Least Terns feed on fish and are at risk of accumulating contaminants found in San Francisco Bay. These contaminants, in great enough concentrations, can affect survival and breeding success (California Least Tern, 2011). Having clean air and water would be a lot healthier for the tern, because it eats mostly anchovy, smelt, silver sides, shiner surf-perch and small crustaceans (Baird, 2010). These organisms accumulate contaminants, so, if the bird’s food source feeds on polluted organisms, that would be transferred to its body, which causes a lot of damage, like limit the ability of the eggs to breathe, and could also cause death in chicks and adults by hypothermia (California least tern (5-year review, 2006)!

       Materials that are in the water, like plastic wrappers, plastic bags, and straws can also kill other animals by intoxication or choking. Plastics have lots of toxins that harm the health of marine animals, such as heavy metals, pesticides, and more. Other than death, these chemicals can cause psychological problems and stress (Lee, K., 2010).

       Loss of common prey species, like the tern already experienced when the region-wide anchovy crash happened in 2009, can cause fewer feedings to chicks (there are usually 2 to 3 per nest) (California Least Tern, 2017) , nutritional deficiencies, and higher rates of baby birds death (California Least Tern, 2011). The anchovy crash was probably caused by a combination of climate change and overfishing (one more time, caused by humans). In just three years, the population of these tiny ocean fish experienced a 99% decline - from more than 1 million tons down to 15,000 tons - (Lehman, 2017)!

Land Management and Beach Recreation 

       For this precious bird to survive, density dependence is something that is really important! Density dependence is a process by which things like survival, and fecundity of the population’s growth rate are dependent on the density of the population itself  (Lewison, 2014). This process is often affected by land management and other human activities (Hamer & Benton, 2015). Things like that leave the little birds exposed to many dangers! Some of them are temperature stress, predation from gulls and crows and even abandonment, if the disturbance is so severe or so long that parent birds become too stressed out to return to the site. (Maholley, 2017).

       Beach-nesting birds are easily flushed off their nests and separated from their young chicks by severe human disturbance on its habitat. Humans affect beaches due to a large number of tourists, increasing water and air pollution. Because of that, the bird’s nesting site is being separated from the ocean, where its food is located, and can also bury it, suffocating the poor and innocents baby birds (5-year review, 2006).

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Other environmental threats to the California Least Tern include:

  • ​​Low flying aircraft - flush adult terns from their nests, leaving young and eggs vulnerable to predators and unfavorable weather conditions (California Least Tern, 2011).

  • Off-leash dogs - can chase the birds, causing stress and a waste of their precious energy; chasing can also kill adults and chicks (Pocket guide to beach birds of California, 2009).

  • Encroaching vegetation - reduces the nesting area available to the birds (California Least Tern, 2011). The California least tern needs bare ground for nesting and roosting. Encroachment of  mostly non native vegetation, such as the ice plant which was introduced on our environment by the military long ago (CDFW, 2016), can make the nesting site useless (5-year review, 2006).

  • Avian predators - Falcons, hawks, owls, crows, and ravens are avian predators that prey upon adult and young Tern, taking away its chance to reproduce. In addition, human activities, such as altering native habitat, result in higher than normal predator populations (California Least Tern, 2011).

Courtesy of Starkov
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