Wednesday, March 26, 2014

A Brief Excursion into a Northern Spring‏

Azure butterfly
Those of us who are snowbirds in Florida generally avoid heading north until the weather is pretty warm in the mid-northern latitudes.  However family business took me to NC/VA in mid March and I had a pleasant if somewhat chilly time exploring the natural history of some early spring ecosystems from the NC Piedmont to the VA Blue Ridge.  There were numerous signs of spring in the activities of animals but the icy grip of winter was still tenaciously clinging to the landscape.  
Bill's cabin at his farm in Chapel Hill, NC

A view of my "contemplation cabin" on our VA farm shows the lack of leaves on trees and the small amount of green vegetation.  Yet there were several amphibians breeding in the ponds- the wood frogs had laid eggs, spring peepers were calling, and the newts were showing reproductive interactions.  Wood frog eggs are usually laid together in large communal masses on the sunny side of ponds at the surface to take advantage of the
Wood frong eggs in pond
 warmest areas; this serves to accelerate development of the tadpoles.  Many ponds are ephemeral and it is advantageous for the frogs to metamorphose sooner rather than later.

On sunny days there were butterflies in flight; here I show a beautiful spring azure that was catching some sunny rays in a spot protected from the wind.  Some other insects were still awaiting warmer weather- a mantis egg case found in a bush will not hatch probably for several months.
Mantis egg case

Birds are quite indicative of seasonal changes.  Tree swallows suddenly showed up one day at our farm although we believe that these are birds that will head further north to breed and be replaced by later migrants that are our own breeding birds.  Hermit thrushes were present at much lower elevations than they will be found when they later breed.  
Yellow-rumped warbler

Yellow-rumped warblers were also staging at latitudes lower than their breeding sites, awaiting better weather for northerly migration.  "Rumps"  are better suited than any other warblers for remaining fairly far north during the winter and migrating earlier since they can feed on berries or even suet.  Note the icicles hanging on this suet feeder in the NC Piedmont on March 14!  It is a risky proposition for birds to migrate north early since they can often be caught by ice and snow storms.  Perhaps the opportunity to reach breeding grounds earlier and to avoid long migrations to the tropics in winter compensates for this type of mortality. We can help them out by planting bushes that provide winter and early spring supplies of small fruits that they enjoy such as wax myrtle and various viburnums. 

So observe and enjoy the signs of spring wherever you are located and think about the myriad and different adaptations of animals to the seasonal changes that are occurring.
Newt in pond
Hermit thrush

 Bill Dunson

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