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A Talk on the Wild Side.

Vermont: Climate Change Poses Challenges for the Bicknell’s Thrush

Bicknell's thrush perched in an evergreen

Bicknell’s thrush nest in mountain-top evergreen forests in Vermont, areas that are shrinking due to global warming. Photo: © T.B. Ryder

Watch a video of a Bicknell’s thrush feeding her young.

Bicknell’s thrush has one of the most restricted breeding ranges of any North American bird, nesting primarily in stunted spruce-fir forests found at or near the highest elevations of mountains in Vermont and other New England states. These mountain tops are like a chain of islands separated by a sea of habitat that is unsuitable for this species.

As the climate warms and precipitation patterns change, deciduous trees – those that shed their leaves in the fall – are likely to become more prevalent in higher elevations, shrinking the size of the mountain-top evergreen conifer forests that are home to the Bicknell's thrush.

This is just one of many challenges that climate change poses for the rare bird.

Another potential threat is a mismatch between the arrival time in spring of Bicknell’s thrush and other birds, which is regulated by day length, and the abundance of insect prey, linked to temperature. If the peak food supply for birds comes earlier due to warmer spring temperatures, late arriving birds may lay fewer eggs and produce offspring that have less chance of reaching adulthood.

The red squirrel, which also lives in the mountain-top forests, also presents a danger. The squirrels feed mainly on spruce and fir cones, but will also raid the nests of Bicknell’s thrush to feed on eggs and young birds.

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Wyoming: ‘Perfect Storm’ Fuels Mountain Pine Beetle Epidemic

An extreme closeup of a mountain pine beetle
Triggered by a “perfect storm” of extended droughts, warm winters, and old, dense forests, mountain pine beetle populations have exploded across a landscape of lodgepole pine trees throughout Colorado and southeastern Wyoming. Photo: USDA Forest Service. Download.

Lodgepole pine forests in parts of Wyoming and other areas of the Intermountain West are being infested by the native mountain pine beetle – a voracious bug smaller than your little fingernail that is thriving in a warming climate.

Triggered by a “perfect storm” of extended droughts, warm winters, and old, dense forests, mountain pine beetle populations have exploded across a landscape of lodgepole pine trees throughout Colorado and southeastern Wyoming.

The mountain pine beetle is a true predator on many western pine trees because to successfully reproduce, the beetles must kill host trees. They typically kill trees already weakened by disease or old age, but even a healthy tree’s defensive mechanisms can be exhausted when beetle numbers are at epidemic levels. The beetle attacks pines in late summer, dispersing a chemical signal that attracts other beetles to mass-attack the tree. When the beetles bore through the bark of the tree, they introduce blue-stain fungus, which can work quickly to kill the tree. Trees stressed by drought and old-age are unable to produce sufficient defenses to fend off beetle attacks. The beetles form tunnels and lay eggs underneath the bark, which hatch into larvae. The larvae spend the winter underneath the bark and emerge as adults in the summer, beginning the cycle again.

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Arizona: As Vegetation Moves to Higher Elevations, What Happens to the Pollinators?

Bee on a yellow flower
Bee on flower. Credit: USFWS.

Bees do it.  Flies do it.  Pollinate, that is. 

But what happens when the piñon and Ponderosa pines and aspens of northern Arizona -- vegetation pollinators call home -- move up the mountain as precipitation patterns change due to climate change? 

Some pollinators rely on specific plants.  But can they use a broader spectrum of plants?  Can they live at higher elevations to get to the plants they need? And what if they can’t?

The U.S. Fish and Wildlife Service’s Arizona Ecological Services Field Office is addressing those research questions as it works at five sites with the Merriam-Powell Center for Environmental Research Center at Northern Arizona University to compile the first-ever baseline about the diversity and behavior of pollinating insects at varied elevations in northern Arizona. 

Pine trees and mountains

Changes in the precipitation patterns in northern Arizona are affecting Ponderosa pine in the highest elevations of the San Francisco Peaks. Photo by Ron Hemberger/USFWS

Pollinators are critical to maintaining diverse, healthy ecosystems. The Service is entrusted to protect at-risk pollinators, such as hummingbirds and pollinators on national wildlife refuges – and threatened or endangered species that rely on animal pollination.  More than 75 percent of flowering plants, which provide fruits, seeds nuts, and nectar for wildlife, depend on pollinators.  Recent studies indicate some pollinators are already being impacted by climate change.

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