The highlight of this year’s annual meeting was a talk by Dr. Robert Askins, the Katherine Blunt Professor of Biology at Connecticut College, who is an expert in forests around the globe. He gave a broad-brush description of the status of northeastern forests through the lens of forest bird species and their habitat needs.
A forest is not just a forest, Dr. Atkins told the group, but a dynamic changing ecosystem that evolves through several stages through a process called succession. Most forest bird species are adapted to living and breeding in one of these stages. Early successional habitats of grasses, herbaceous plants and shrubs, such as GOSA is restoring on Candlewood Ridge, are among the rarer habitats in our area. Historically, they were created by beavers, blow-downs and fire, but human development and forest fragmentation have reduced their roles in forest succession.
Many of our songbirds, including a number of warblers, depend on this early successional habitat with its rich supply of seeds and berries. Birds of our shrubby forest areas such as the brown thrasher, yellow-breasted chat and blue-winged warbler are in steep decline. Power line corridors, which contain early successional forest in a permanent state, can be especially important because native plants are well established there, often outcompeting invasives.
While Connecticut is pretty much devoid of old growth forest (250+ years), it still contains considerable areas of mature and young forests, which are essential habitats for most of our forest birds. Rose-breasted grosbeaks, redstarts and other warblers breed in our young forests, while scarlet tanagers, ovenbirds and wood thrushes hang out in more mature forests.
Threats to our forests, and therefore our forest birds, are considerable. Dr. Askins presented slides showing the steady forest fragmentation in Connecticut since the 1980s. Many birds of the mature forest require large tracts of unbroken forest to breed successfully and avoid the parasitism of cowbirds. Perhaps the biggest threat, however, are the alien invasive species from other continents such as the hemlock woolly adelgid, an insect which is decimating hemlocks in the Northeast and elsewhere. We know all too well the loss of our chestnut trees, once the anchor species of the northeastern forest, to chestnut blight, and the loss of our majestic elms to Dutch elm disease. Fast approaching is the emerald ash borer, which some scientists fear will wipe out virtually all ash trees, and the Asian longhorn beetle, which seems to have a gourmand appetite for many tree species. Hope lies in finding natural predators for these invaders, predators that are specific to an individual species. A promising predator for the hemlock woolly adelgid is a lady beetle from Japan, which experimental tests have shown feeds solely on these insects and will not survive without an adelgid diet.
Another major threat to the forest is the burgeoning deer population. Research has shown that the forest has a threshold of 22 deer per square mile. More than that and tree seedlings become browsed out of the forest, slowing or even stopping forest regeneration.
Dr. Askins remains optimistic, however, that our northeastern forest birds are resilient and will be able to adjust to changes in their ecosystem. Species will shift their ranges, he concluded, as they have during numerous periods of major climate change in the past, though perhaps now with a little help from us. Deciduous forests are resilient, but other habitats, such as tidal marshes and alpine meadows, are threatened by climate change.