Loss of natural habitat, caused by everything from invasive species to climate change, is causing an alarming loss of bird population in Cabin John and throughout North America, Clive Harris told the 45 or so attendees of the March 30 CJCA meeting.
Clive, an avid birder and past president of the Montgomery Bird Club, focused his talk on birds that breed in Cabin John. Using photographs and snippets of taped bird calls, Clive introduced the audience to dozens of bird species, while noting that when out birding about 80 percent of the birds are heard and only about 20 percent are seen.
Roughly half of the 110 to 120 breeding bird species in Montgomery County are migratory, wintering as far south as the Andes Mountains in South America and returning here year after year to breed. This means they are also vulnerable to habitat issues where they winter.
Clive cited a recent study by the journal Science that found North America has lost more than a quarter of its bird population, some three billion birds, since 1970!
In Cabin John, more homes and lawns, too many deer, and the growth of invasive plants are impacting the local bird habitat. Clive explained that all birds feed their young insects and non-native vegetation does not support as many insects as native plants. In the case of Chickadees, if more than 30 percent of the vegetation is invasive, the species cannot maintain its population.
The Wood Thrush, a migratory bird that winters in Central America and crosses the Gulf of Mexico in a single night’s flight as it comes north in the spring, is in jeopardy because of habitat loss in its wintering grounds and here where it breeds. Clive explained that the large deer population feeds on the underbrush where they build their nests, not only decreasing their food supply but making them vulnerable to predators.
But not all bird populations are declining. Pesticide bans in the 1970s have led to increases in Raptor populations. Clive said there appear to be a growing number of Bald Eagles, who partner for life, nesting high in the trees along the Potomac River north of Cabin John.
A pair of Peregrine Falcons have been present on the American Legion Bridge for more than 15 years, Clive noted, apparently the first breeding pair in the county since the 1940s. You can follow a track down by the south side of the bridge, all the way to the river to view them. A nesting box was placed on the bridge and is used by the falcons during the breeding season.
Clive ended his talk with a list of things we can do to protect birds:
Protect birds from window collisions
Over one billion birds die each year due to striking window glass, with roughly half being collisions with windows in homes and other low-rise structures. In addition to screens, decals, and other alterations to the windows, one easy way to reduce threats is to place bird feeders well away from your windows.
Keep your cat inside, or outside in an enclosed location
Free-ranging cats kill more birds than any other direct threat – some 2.4 billion birds a year in the United States alone, according to the American Bird Conservancy.
Improve your backyard habitat
Gardens full of exotic and non-native plants do not support the native bird population. The reason is simple – native plants support native insects and with a few exceptions, all birds, even seedeaters, feed insects to their chicks.
Native plants also provide the seeds, berries, and nectar to which our birds are adapted. (In fact, berries of some widely planted exotics such as Nandina, are toxic to birds.) Trees and shrubs also provide shelter and nesting sites for birds.
Reduce pesticide use
Some pesticides pose an immediate threat to birds, while others impact insects upon which birds depend. Neonicotinoids like imidacloprid are widely-used, systemic pesticides which are transferred to all parts of the treated plant, including seeds, leaves, nectar, and pollen.
Wholesale spraying for mosquitoes is also a threat to birds. Despite what their websites promise, the sprays used by “mosquito control” companies promoting “pest-free” yards contain synthetic pyrethroids, which kill all insects that land on the treated leaves. We all are aware of the ongoing decline of insects – “the insect apocalypse” in the words of some scientists – and much of this is due to overuse of pesticides. No insects = no birds.
Provide food, water, and nesting sites
Most of us feed birds, and those with sufficient space may also provide water and nest-boxes. In addition to placing bird feeders away from windows, they should be sited near vegetation to provide cover.
Feeders also should also be cleaned regularly to avoid avian diseases passing bird to bird. Sterilize hummingbird feeders regularly, and in hot weather, change the nectar frequently.
Birdbaths or fountains need their water changed frequently – daily in hot weather – to avoid mosquitoes and to prevent the spread of bacterial disease.
Nest-boxes must be carefully sited to avoid predators and other hazards. Since box designs, which target individual species, vary so much, seek out advice from such websites as NestWatch from The Cornell Laboratory of Ornithology.
By Susan Shipp