Forest Journal: Aviary reminders of summer's swiftness
DAVE ANDERSON |
July 04. 2014 11:50PM
Carefully woven, a local tapestry of territories lies tattered and torn.
Bereft of song; obsolete and forlorn.
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BUZZKILL alert: Early-morning news from the forest reveals the earliest autumn preparations are now underway in avian fashion and music. Spring celebrities including electric orange orioles, stunning scarlet tanagers and neon-blue buntings all soon will fly low under the radar as breeding season ends.
Bright colors of spring are slipping out of fashion. The colors fade, having served their intended purposes.
Male birds' conspicuous plumage is designed to attract potential mates, warn-off rivals and divert attention of nest predators from furtive females wearing neutral hues - gray, white, yellow and olive green. Concealment plumage works better for females brooding vulnerable chicks in hidden nests. The bright colors are passé, an avian fashion faux pas.
With mating, nest-building, eggs and nestling stages now over, fledglings are afield. I've recently seen families - bluebirds, robins, blue jays, sparrows - leaving nests behind. Fledglings beg parents for food and fly unsteadily while testing their wings and learning to forage for insects, berries and seeds.
As July day-length ebbs, bird reproductive hormones plummet, triggering physical changes. Bright plumage feathers molt to be replaced with drab traveling attire. Birds' reproductive organs shrink to save weight and body space. Breeding season baggage only hinders flight. Carry-on luggage gets smaller as families disperse to feed and grow.
The forest is already much quieter during the dawn birdsong chorus. The males' obsession with ceaseless singing to maintain and defend territories from rivals is no longer important. The energy expended singing, flashing bright colors, impressing ladies and chasing off rivals during May and June is now conserved - hence the tattered and torn, bereft and forlorn state of that tapestry of territories.
The morning chorus still rings out at dawn with notes of vireos and winter wrens, supported by an orchestra of ovenbird warblers. But the swelling symphony has quieted to a soft reprise, well-past its late May crescendo. One lone, speckled-breast wood thrush repeats its haunting spring flute-song - "Eee-o-lait!" - in dim pre-dawn woods. The notes rouse me from sleep and foretell that autumn is creeping - even before pumpkin vines have begun to set flower.
Adult birds are now free of territorial imperatives and parental responsibilities. Empty-nest syndrome arrives with the increased safety of not being seen. Avian summer vacation is time to molt, rest and feed heavily to prepare for autumn migration after the rigors of breeding and raising chicks.
'... and the living is easy'
Summer fare features abundant insect proteins and a surge of sugary plant-carbohydrates derived from fruits and seeds. Summer fruits provide high sugar-content carbohydrates - quick-energy calories. Late summer fruits provide slower-burning lipids -fats that fuel long-distance migration. Adults and fledglings alike reap quick bursts of energy from the progression of sun-ripened berries: strawberries, raspberries, red and black elderberries, blueberries.
By summer's end, birds eat waxier fruits of wetland shrubs and vines, including sumac and poison ivy. Insects and weed seeds add protein essential to fuel the growth of fledglings. Development of sleek new feathers, hollow bones and strong breast muscles will enable their departing flights in fall.
Migratory birds must mature quickly and prepare to leave. They build muscle and ample fat reserves to travel hundreds of miles. The feat is all the more amazing for fledglings just weeks out of their egg shells come Labor Day.
How do fledglings navigate to distant, tropical locales they've never seen while unaccompanied or provided with parental guidance? Where does an innate mental map of the Earth's vast oceans and continental geographies reside in tiny bird brains hatched only in the past few weeks?
"Forest Journal" is published every other week in the New Hampshire Sunday News. Naturalist Dave Anderson is Director of Education and Volunteers for the Society for the Protection of New Hampshire Forests. Email him at firstname.lastname@example.org or through the Forest Society website, www.forestsociety.org.