News & Features

10 Year Study Finds Sharp Decline in Black Terns – Possible Tie to Water Management in the Klamath Basin

Black Tern at Lower Klamath National Wildlife Refuge (c) Jim Livaudais 2017

Long-term monitoring efforts show that Black Tern declines in the Klamath Basin are higher than declines previously documented for continental and regional populations. The Klamath Basin is a region extending north and south along the Oregon and California border on the east-slope of the Cascade Range. The region is made up of a mixture of National Wildlife Refuge wetlands and agricultural land and is well known as a birding hotspot. Results from a study conducted by Klamath Bird Observatory from 2001 to 2010 show a steep decline in numbers of Black Terns in the wetlands and open waters of Agency Lake and Upper Klamath Lake, both located in the northern extent of the Klamath Basin.

Klamath Bird Observatory Science Director and the study’s lead author Jaime Stephens points out, “Black Tern populations in North America experienced steep declines prior to 1980, likely a result of dramatic wetland habitat loss. The current population is estimated to be about one-third of its historical size — reversing declines has become a conservation priority. Our findings suggest an alarming decline of 8% loss annually at Agency and Upper Klamath Lakes.”

According to a Black Tern conservation plan created in 2006, the desired population objective within the Great Basin — which includes the Klamath Basin — is 10,000 individuals. The current estimate of Black Terns for this area is already some 20% below the objective, making these local declines a red flag. The aforementioned 2006 Intermountain West Waterbird Conservation Plan was created by researchers and managers from multiple organizations and agencies to identify and fill knowledge gaps and aid in all-bird conservation efforts. Conservation plans are developed, in part, by looking at historical and current population numbers to create reasonable objectives for maintaining populations, with a goal to prevent costly special-protection actions such as threatened or endangered species listing.

Terns are migratory waterbirds related to gulls. Many tern species travel to inland waterbodies to nest and return to coastal areas for most of the year. The Black Tern is one of the smallest terns in the world, with a graceful, floating flying appearance. It is a long-distance migrant, nesting in wetlands across the northern United States and southern Canada and wintering along South America’s northern coasts. Long-term Black Tern population declines have been attributed to degradation and loss of wetland habitat across North America. Now, research is needed on habitat suitability (e.g., water levels and their effects on habitat availability, water quality) and population dynamics to determine how the species’ needs can be met in remaining wetlands.

Klamath Basin National Wildlife Refuge Complex manager Greg Austin said, “We find these results reflective of the declines observed in wetland habitat throughout the Klamath Basin. Historically, the refuges provided the necessary habitats to support Black Tern populations, however with the loss of wetland habitat throughout the Klamath Basin, Black Tern populations have declined. The Klamath Basin is an over-allocated system; drought and increased demands on water resources have put the Klamath Basin out of balance; there is not enough water to completely satisfy every need every year. A balanced approach for water allocation in the Basin is needed for effective management by all stakeholders.”

KBO’s Stephens explained the importance of this study’s results, “It is not well understood how water levels in the Klamath Basin relate to how much Black Tern breeding season habitat is available and how good that habitat is for raising young. Given the challenges that Black Terns face from a combination of water allocation, drought, and climate change impacts, an improved understanding local habitat needs is pressing.”

She added, “The best next step to addressing local Black Tern population loss is to determine the cause of the decline we found.”

The results of the 2001-2010 Klamath Basin Black Tern study were published in the Winter 2015 issue of the Northwestern Naturalist journal. To read or download the publication, click here.

What can birders do?

You can help in the efforts to better understand Black Tern populations throughout the Northwest by birding your local wetlands and submitting eBird checklists. Additional information can be extremely helpful to know if the birds are not just moving through an area, but if they are staying and breeding in the area. While you are out birding if you observe terns (or any other species) using an active nest, gathering nesting material, carrying food, or other breeding behavior remember to add these behaviors to your checklists.

This original article can be found on the Klamath Call Note blog.