Ripples 10-01-15

We are now in the midst of one of the most important times of year for birds.  It seems as though the warm September with south winds held back migration, and now that winds have turned birds are moving in full force.  The past week has been very interesting along the Lakeshore.
Fall migration begins in July, believe it or not, and is well under way by August.  There are huge flights of songbirds during nights in September and October.  They fly at night because there is usually less wind and turbulence, making flight more efficient (easier), especially if there are following winds.  Birds fly for a distance, then land if there is suitable habitat to feed and rest.  Many songbirds follow the shores of large rivers, lakes, and oceans, which makes Manitowoc County an important place on the Great Lakes portion of the Mississippi Flyway migration route.  Birds spend a large amount of energy during their migration flights, and require places with natural habitat patches to replenish their reserves in order to continue.  Near Lake Michigan, every habitat patch, no matter the size, can be important for these birds.  If they can’t find enough feeding and resting areas during migration, we would expect them to arrive at their wintering or nesting places in poor condition, making winter survival or nesting difficult.  This probably contributes to the slow decline that we are seeing in populations of migratory landbirds.
This past week, the north winds brought thousands of birds to Woodland Dunes, especially warblers, kinglets, and sparrows.  Gentle winds at night allowed birds to fly, which can be easily tracked on radar, then strong daytime breezes caused them to stay close to the ground in the cover of brush and the forest.  One of our staff described seeing dogwood shrubs “dripping” with dozens of small birds, while in the forests along Columbus St., including Zander Park next to us, there were thousands of yellow-rumped and palm warblers, golden-crowned kinglets, white-crowned sparrows, and even flocks of common redpolls, all having recently departed Canada and on their way to the southern US.  
When we catch and band birds, we can see the amount of fat they have stored beneath the skin of their chests- around the keelbone or wishbone. Birds are able to quickly store and then metabolize fat.  They deplete these stores during long migratory flights, then replenish those reserves in a few days of feeding if the habitat they find is good.  They feed on a combination of insects, fruit, and for some, seeds.  Dogwoods and native viburnums, sumacs, and other shrubs can be very good food sources for migrants.  Exotic plants such as buckthorn and honeysuckle, although they produce loads of berries, are not as nutritious as the berries of native plants for the birds that live here, and are suspected of being harmful overall if they replace native plants.  Wherever possible, if even only a shrub or two, it’s beneficial to plant native fruit-bearing plants.  At the same time, it’s equally important to remove escaped non-natives from the landscape.
It is hard to describe the wonder one experiences when in the forest surrounded by hundreds of these migratory birds, watching them busily forage among the still green leaves.  If you’re in the woods at the right time, this activity will be all around you, enhanced by whirling flights of flocks of finches moving at high speeds through the trees and shrubs.  These semi-annual invasions have taken place for thousands of years, and help distribute life and energy throughout ecosystems.  They are another of nature’s wonders to be appreciated and studied, and, we hope, conserved so that future generations can continue to marvel.

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