It is well known that animals may often reveal things that are wrong with the environment as bioindicators; thus recent observations of bird behavior are some cause for alarm. While it is of course normal for birds to migrate south in the winter, when they move far outside their typical winter ranges there could be some cause for concern, sufficient to lead us to examine the occurrences that are unusual and to seek rational explanations for them.
The strange thing about bird migration this winter is that movements have been recorded far south of the typical range on both sea and land. If a common cause is involved, this could indicate a hemispheric or world wide change that needs to be studied. If you think about the conditions in the far north (see photo from the winter forest in Idaho), it is perhaps not surprising that birds would want to migrate south, perhaps to a balmy beach in the SW coast of Florida (see photo of beach on Knight Island). However things are not always so simple. Northern birds are adapted not only to cold but to 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.
This strategy, a southward movement during winter, has been very successful for many birds. For example white pelicans leave western inland wetlands of N. America and winter along the Gulf coast. Their size and habits of feeding are quite different from the 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 salt water 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 and they reached even the Florida gulf coast in some numbers. I show a photo of an adult razorbill from Maine where they breed and a photo of a dead immature razorbill on the beach of Knight Island, Florida. 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 storm Sandy. We do know that they have now 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 that such abnormal migratory events in the past may have led to the current successful patterns of trans-continental 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 their normal winter ranges. I show a photo of a redpoll and an evening grosbeak, two of these northern wanderers which are being seen in the Carolinas. A snowy owl has even been sighted in coastal Georgia!
What could possibly explain such fluctuations in both the marine and terrestrial environments? Or is it only coincidence that 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.
Bill Dunson, Englewood, FL & Galax, VA