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State of the Birds Report

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Islands

Rising sea levels and temperatures threaten birds.

 


Akekee_EricVanderWerf_smallbanner.jpg  

 

                  Noteworthy

93% of Hawaiian birds and 62% of all U.S. Pacific island birds exhibit medium or high vulnerability; 49% of Caribbean  birds also show medium or high vulnerability to climate change.

Characteristics of islands such as small size, frequency of natural disasters, and high degrees of bird endemism contribute to island birds’ high exposure to impacts of climate change.

Increases in temperature and rising sea levels are expected to reduce natural habitats on islands where bird species have restricted ranges and a limited ability to respond to change.

Lower rainfall in the Caribbean will cause changes in the distribution of habitat types, reduction in the amount of moist forests, and disruptions in food supplies.
 

Image: 'Akeke'e by Eric VanderWerf   

Observations and Predictions

Increases in temperature and rising sea levels are expected to reduce the extent of natural habitats on islands where many bird species have restricted ranges and a limited ability to respond to change. Species that depend on mountain forests, coastal wetlands, and low-lying islands are expected to be most severely affected by this direct habitat loss.

Over the last century, average annual temperatures in the Caribbean have increased by more than 1°F and during this century they are expected to rise by an additional 4°F. In the U.S. Pacific islands, temperatures have risen by 0.5°F during the past century and are expected to rise by an additional 4°F by 2090. The Caribbean has been drying in recent decades and this trend is expected to continue with a reduction in summer rainfall.

Tropical cyclones are expected to increase in intensity. Sea-level rise is expected to reduce the area of low-lying islands and eliminate or degrade inshore habitats, including mangroves and other coastal wetlands. In addition, sea-level rise will cause saltwater intrusion into freshwater underlying islands, causing salinization of soil and freshwater wetlands, especially on low-lying islands.

Bird Species Vulnerability

For this report, island birds refers to upland (for example, forest or scrub) and wetland birds occurring in Hawai’i or on U.S. associated islands in the Pacific and Caribbean. (See Oceans for a discussion of island-nesting seabirds).

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Laysan Duck by Roy Lowe

Hawaiian birds are severely threatened by climate change. Among the 42 native and endemic species of the Hawaiian Islands, only one is not considered of conservation concern. Multiple attributes contribute to their vulnerability to climate change. Attributes that are most important include single island endemism, reduced dispersal ability, and exposure to climate change of the habitats on which these birds depend, particularly high-elevation mountain forests.

 

HawaiianPie_p12.jpg 93% of Hawaiian birds exhibit medium or high vulnerability to climate change.
PacificIslandsPie_p12.jpg 62% of all U.S. Pacific island birds show medium or high vulnerability.
CaribbeanPie_p12.jpg 49% of U.S. Caribbean island birds assessed have medium or high vulnerability to climate change.


Potential Impacts

In Hawai’i , species restricted largely to high elevation forest, such as Puaiohi and 'Akiapōlā`au, will be highly susceptible to increases in temperature. Elsewhere, mountain species such as Elfinwoods Warbler on Puerto Rico and the Rota Bridled White-eye in the Northern Mariana Islands will face similar threats. Sea-level rise will also reduce habitat for species such as Laysan Duck and Laysan Finch in Hawai’i and Greater Flamingo in the Caribbean, and may threaten coastal forests important to the Micronesian Megapode in Northern Mariana Islands.

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Hanawi Natural Area Reserve in
Maui by George Wallace

There is a strong relationship between precipitation and insect abundance. With climate change, rainfall is expected to decline in the Greater Antilles, potentially leading to a persistent pattern of low insect abundance and a reduction in bird breeding success, which could result in significant long-term population declines, especially among insectivorous species of concern such as Puerto Rican Vireo. In addition, reduced rainfall may reduce the survivorship of overwintering Nearctic-Neotropical migrants.

Cyclones disrupt the food supplies of some bird species, especially those that depend on fruit and nectar, causing post-storm population decreases among species with limited ability to disperse long distances in search of food. The intensification of subtropical and tropical cyclones expected with rising temperatures and shifting ocean currents will exacerbate the impacts of invasive plants by causing large-scale habitat disturbance, creating opportunities for invasive species to rapidly expand their ranges.

On the main Hawaiian Islands, avian malaria and pox spread by introduced mosquitoes pose a significant threat to native Hawaiian birds, which have little or no natural resistance to these diseases. At temperatures below 55°F, which occur
today, typically around 5,000 feet above sea level and higher, the malaria parasite will not completely develop in birds. An increase in temperature of slightly less than 4°F, which is predicted by some models, would raise the 55°F threshold by nearly 1,000 feet, greatly reducing the areas in which there is a low risk of disease transmission. For example, the Hanawi Natural Area Reserve on Maui could lose 57% of its remaining low-risk area, increasing the risk of malaria to endangered Maui Parrotbill and Ākohekohe.

All forested areas on Kaua’i and O’ahu are warm enough for some level of malaria transmission. However, warming on Kaua’i would result in an 85% decrease in the area where transmission is currently highly seasonal and limited, contributing to further declines among imperiled species such as ‘Akeke‘e and ‘Akikiki.

 

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`Akiapōlā`au by Jack Jeffrey
Key Steps
 

On all U.S. islands, immediate protection and restoration of natural systems is critical to counteract the negative effects of climate change. Protected areas need to be large and numerous to ensure that each important habitat type is protected across islands. Protection and restoration of high elevation habitats is essential. 

Programs to control invasive plants and animals must be supported and implemented. In Hawai’i, until more sophisticated methods are developed to directly control mosquitoes and the diseases they transmit, fencing and removal of ungulates are the most effective means of maintaining habitat quality and reducing the amount of mosquito breeding habitat. 

It is important to focus species recovery efforts now on the species most in danger of becoming extinct. Translocations to create new species populations in multiple locations will be an important strategy. In some cases, it will be necessary to establish captive populations of species that might become extinct. 

Conservation in Action
 

In Hawai’i, watershed partnerships have been effective at pooling resources to undertake more restoration efforts. Strides have also been made in protecting and restoring remaining natural forest. Partnerships including the Hawai’i Department of Lands and Natural Resources, U.S. Fish and Wildlife Service, National Park Service, conservation organizations, and native Hawaiians are working to fence key areas and remove nonnative species. Additionally, predator removal has successfully provided safe places for birds to nest. 

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Akohekohe by Jack Jeffrey

 

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