Birds native to forests on the island of Kauai in Hawaii are disappearing. Researchers predict a surge of extinctions over the next few decades. Climate change and invasive species are thought to be the driving forces behind the rapidly declining bird populations. The findings are in a paper that was just published in the journal Science Advances.
Researchers analyzed data and population trends of forest birds on the island of Kauai over a 25-year period. They also collected data on the prevalence of introduced diseases, such as avian malaria (Plasmodium relictum). In addition, the research team recorded the presence of mosquitoes, non-native birds, and invasive plant species.
The team found that Kauai’s native forest birds are experiencing rapid population declines. For example, Hawaiian honeycreeper populations are dropping and two species are already endangered. An increase in the prevalence and spread of disease was a major driver of these population crashes. Avian malaria, an introduced disease caused by a protist, is devastating to many of Hawaii’s birds. The disease is carried by mosquitoes, which have become much more common in the warming climate.
Invasive species contributed to the decline in forest bird populations. The spread of invasive weeds has resulted in less useable habitat for Hawaiian birds. Non-native birds also pose a problem; they are becoming more common and are capable of outcompeting native species. While the researchers did find evidence of harm caused by invasive species, climate change and disease were still the most important factors at play.
Kauai’s forest birds are struggling to adapt to climate change and disease. Most of the native species are susceptible to avian malaria, a disease that is spreading rapidly due to global warming. Warmer temperatures favor the protist as well as the disease’s vector, mosquitoes. While invasive plant and bird species are also a problem for native birds, the authors recommend that conservation efforts focus on eradicating disease. Reducing mosquito populations could help save Kauai’s forest birds. The research team warns that as climate change continues, other island bird populations will be at risk. Island birds are especially vulnerable to climate change because they are effectively trapped, unable to search for more suitable habitats.
Eben H. Paxton et al. Collapsing avian community on a Hawaiian island. Science Advances (2016).