The Remarkable Migration of the Red-Necked Phalarope

December 1, 2010

Nature Notes by Bill Dunson

 

I am sure that each of us has favorite places on the planet where we are particularly fond of enjoying Nature. However it is beneficial for the mind to leave these special places occasionally and venture out into new habitats where unfamiliar creatures challenge our mental complacency. I had the opportunity recently to visit what for me as an Eastern North American inhabitant is a “foreign” place, namely Utah. One of the more bizarre habitats in Utah is the Great Salt Lake, which is the remnant of a much larger Lake Bonneville. It has no outlets and thus the large amounts of fresh water lost to evaporation in this desert-like climate result in salts being concentrated in the lake to levels of 4-28%. If you compare this to the ocean at about 3.5% salt you can understand why there are no fish in the lake and that aquatic productivity is concentrated mainly in a type of zooplankton, the brine shrimp ( a fairy shrimp – Artemia ) and an insect, the brine fly, around the shores. This results in some huge concentrations of water birds that can eat such small prey which is present in enormous amounts.

One effective way to experience the Great Salt Lake is to drive across a causeway to Antelope Island, where there is a state park and some interesting terrestrial wildlife. However my wife and I found that the causeway itself was more interesting in early September when shorebird migration is in progress. We observed huge numbers of avocets, black-necked stilts, eared grebes, and most amazing of all, red-necked phalaropes in migration. In particular, north of the causeway bridge nearest the island there were hundreds of red-necked phalaropes feeding where the water was turbulent as it flowed from the bay to the south into the main lake. This appeared to bring brine shrimp to the surface and allowed the phalaropes to feed without performing their strange spinning behavior. These phalaropes were migrating from their breeding grounds in the Canadian tundra to wintering areas in the ocean off the western coast of S. America. So the chance to feed on an abundant food source along this ancestral and rather remarkable migratory pathway is obviously crucial to their ability to make this long journey. Another example of this process is the role of Delaware Bay horseshoe crab eggs in fueling the migration of shorebirds along the east coast of N. America.

Phalaropes have long been known for their strange reproductive behavior whereby the roles of males and females are reversed. The females are more colorful, mate with multiple males and relegate the “Mr. Mom” role to the males! Apparently this allows the females to be more prolific; what the males think about this process is unclear but apparently for the species as a whole there is greater fecundity.

It is interesting to think also about the possible means by which such a bizarre pathway of migration might have originated. It is unusual for a freshwater animal to live in salt water habitat, not to mention as a pelagic organism without contact with land for the entire winter. Indeed it is hard to imagine how such a small and seemingly fragile bird could survive out to sea for months at a time. But clearly phalaropes are well adapted for their life at sea and have adopted a breeding behavior that utilizes a far northern freshwater habitat with abundant small prey which is only available to them for a short period of time during the summer. We will never know exactly how this unusual life history originated, but we can marvel at the extreme adaptations in structure, physiology, biochemistry and behavior that make it possible.

So watch out during the Fall and Spring seasons for migrants of all types that will be passing through your home space and think about the amazing variety of life histories that have developed to exploit food wherever it is found.

Bill Dunson, Englewood, FL & Galax, VA
wdunson@comcast.net

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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