Animal bio-indicators often reveal environmental concerns. Recent observations of bird behavior are Gasparilla Island are possibly cause for alarm.
It is normal for birds to migrate south in the winter but when they move far outside typical winter ranges there could be some cause for concern.
Let's examine recent unusual occurrences and seek rational explanations for them.
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White pelicans leave western inland North American wetlands to winter along the Gulf Goast. Their size and feeding habits are different from brown pelicans, but they do well in Florida, too.
Strangely, bird migrations this winter have been recorded far south of the typical range on sea and land. If a common cause is involved, this could indicate a hemispheric or worldwide change.
Cold conditions in the far north make it perhaps not surprising birds would migrate south, perhaps to a balmy beach on Gasparilla Island.
However, migration deviation rationales are not always so simple. Northern birds are adapted to cold and feeding on a certain type of seeds, insects or fish. This may not be available in the south. Yet if conditions are too severe in the north, birds may migrate in the hope of finding better circumstances somewhere else.
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William Dunson, Ph.d., professor emeritus of biology at Penn State University, splits time between Southwest Florida and his farm in Galax, Va. He can be reached at wdunson@comcast.net.
This strategic southward movement during winter has been successful for many birds.
For example, white pelicans leave western inland wetlands of North America to winter along the Gulf Goast. Their size and habits of feeding are quite different from local brown pelicans, but they do well in Florida.
Similarly, common loons fly south from their northern fresh water breeding lakes and some winter in saltwater in Florida, where they dive for fish. Some gannets migrate south from maritime Canada in large flocks that circumnavigate the Florida peninsula to reach the Gulf. These species have well-established migratory pathways and return to northern latitudes to breed in summer.
However a most unusual movement or "invasion" of northern seabirds, especially razorbills, occurred this winter in some numbers. This large migration is unprecedented and we can only speculate about the reasons.
Perhaps these mostly young birds ran out of food in the north due to unusual sea conditions caused by the Superstorm Sandy. They encountered an outbreak of red tide along the Gulf Coast, which may be directly toxic to them or reduce their food supply. One could even speculate such abnormal migratory events in the past may have led to successful patterns of transcontinental migration, but the number of failures must have greatly outnumbered the successes.
One of the strangest features of this abnormal avian winter migration is that on land, mass movements of northern birds are also occurring far to the south. This has been called a "finch" explosion with numbers of pine siskins, redpolls, evening grosbeaks, red-breasted nuthatches, purple finches and crossbills being seen far south of normal winter ranges. I show a photo of a redpoll and an evening grosbeak, two of these northern wanderers seen in the Carolinas. A snowy owl has even been sighted in coastal Georgia!
How to explain fluctuations in marine and terrestrial environments? Is it only coincidence these events are occurring simultaneously this year?
It is easy to blame global warming, marine storms, or possibly human-caused hemispheric fluctuations, but it is quite difficult to obtain reliable evidence to eliminate hypotheses.
Is this phenomenon due to a temporary disruption in northern ecosystems, or does it presage a long-term doomsday scenario?
The birds are telling us something and we had better listen for our own protection and that of our environment with which we are inextricably connected.
William Dunson, Ph.d., professor emeritus of biology at Penn State University, splits time between Southwest Florida and his farm in Galax, Va. He can be reached at wdunson@comcast.net.
