In recent years, Colorado’s lodgepole and mixed-pine forests have been hit by a massive infestation of mountain pine beetles, transforming nearly two million acres from a sea of green into a sea of rust. The tiny mountain pine beetle is a Colorado native that can attack all pines, but it favors the old, dense forests that dominate our state’s landscape. While both beetle infestations and change are natural to forests, it’s sometimes difficult to see an upside. Surprisingly, there is one.
Many species of wildlife depend upon insects and disease organisms to create habitat or provide food. The winners per se in the current mountain pine beetle epidemic are species as varied as black bears and chickadees, woodpeckers and white-crowned sparrows, mice and mountain bluebirds, nuthatches and elk, green-tailed towhee and the brilliantly colored western tanager.
For insect-eating birds, which include all the birds just mentioned, the bark beetle infestation is a gold rush. More beetles mean more food, better breeding success, and improved winter survival. Hairy woodpeckers are one of the first birds to take advantage of the food bonanza. More than 75 percent of their diet is made up of insects, particularly bark beetle larvae. Of course, the woodpeckers need a place to stay while feasting on the beetle cornucopia. They are primary cavity-nesters, which means they are capable of excavating their own nests in dying snags (standing, dead trees) or nearby aspen. Other less capable birds can then come in (secondary cavity nesters). These secondary nesting birds comprise up to one-third of the breeding birds found in some forests. Nuthatches, chickadees, and even squirrels will use holes excavated by large woodpeckers.
Beetle infestations benefit more than birds. When beetles kill 50 to 75 percent of the trees, the canopy is opened up, allowing sunlight to reach the ground. At the same time, nutrients that were locked up in the living trees are now available to grow grass and shrubs. Deer, elk, bear, and other species gain high quality forage. Ground-nesting birds, such as juncos and white-crowned sparrows, benefit from the increased ground cover. Snowshoe hares, voles, and deer mice benefit both from the denser ground cover both for increased forage and hiding cover. As populations in these small mammals increase, this in turn benefits their predators—bobcat, lynx, and marten.
Colorado’s forests are in transition. Not all species will benefit from large areas of beetle-killed trees. The species that don't benefit now will once again flourish, hopefully, as the epidemic subsides and a new generation of pines takes its place. Meanwhile, those that love mountain birds can take advantage of the influx of cavity-nesters and insect-eaters by spending time birding where bird diversity is the greatest—at the edges of beetle infestations.