Sunday, October 25, 2015

A shorebird with bling of a different kind


On Oct. 18, 2015, while walking along the beach on Palm Island, Charlotte County FL, just south of Stump Pass, I noticed one tiny shorebird, a sanderling, that had bands on its legs. This bling was unusual since there were orange bands on both lower legs, a silver band on the upper left, and a blue band and blank white flag on the upper right leg.  There is an on-line website (bandedbirds.org) that allows banded birds to be individually identified if they carry numbered flags, but this combination of bands without a lettered code was confusing.

I contacted the administrator of the website and eventually found that this bird was banded at Chaplin Lake, Saskatchewan, Canada, as a group or cohort of birds caught in the springs of 2012-2014.  This bird was presumably headed to its breeding site in the high Arctic about 1200 miles away along the northern tundra of Canada when banded.  It is now on the SW FL coast where it may spend the winter or head further south.

The direct line distance between Chaplin Lake and Palm Island is about 2000 miles.  Chaplin Lake is unusual in that, like the Great Salt Lake in Utah, it is saline and produces large numbers of brine flies and fairy shrimp that are avidly consumed by vast numbers of migrating shorebirds.  

So the sanderlings which scurry along the beaches in FL are remarkable hemispheric travelers which depend on the health of delicate natural habitats in different countries.  They are tiny (about 2 oz) and their ability to make such a fantastic migratory journey of at least 6000 miles for each round trip over many years is almost beyond comprehension.  

Bill Dunson

Friday, October 23, 2015

Aerial cannibals !

If you are at the beach you might look up and notice that an interesting migration of dragonflies is taking place just over your head.  Dragonflies are heading south to escape the frozen north in considerable numbers and I watched many common green darners passing by at Caspersen beach, Venice, FL, on Oct. 21.  
 
It may surprise you that relatively primitive insects such as dragonflies are capable of such long distance migration.  They are extraordinary flyers but they apparently get hungry while flying and their appetites take a bizarre turn.  This species is common around our farm ponds in VA so it is interesting to see where they go when they leave and are replaced by the equally large, but cool weather tolerant shadow darner.
 
I saw several twosomes of common green darner dragonflies writhing on the road and on closer inspection realized that one of the pair was eating the other! The dragonfly on top had its jaws embedded into the thorax of the victim. I knew that falcons often eat migrating dragonflies but did not realize that these predaceous insects could and would eat their own species.  

Bill Dunson
Englewood, FL