(murmurings at dawn)
Migration is a patterned movement from one place to another that occurs in all major animal groups – birds, mammals, fish, reptiles, amphibians, insects and crustaceans (Migration may also occur at the cellular level).
Migration can occur seasonally or just once in a lifetime. Animals migrate primarily to find food and to reproduce.
It’s important to distinguish between animals that migrate seasonally for food and reproduction from those who are forced to leave one place for another because of human induced habitat loss, insecticidal use, and Climate Change.
Like scientists, I have been intrigued by both processes (one normal, the other not) since we know so little about how animals know what they know, whether theories about migration are true or not, and because unfortunately whatever capabilities animals have developed over millennia are also being interrupted by Climate Change in ways that we can rarely comprehend. Animals must adapt faster than ever before to survive.
Multitudes of studies indicate that migrating species probably use a wide variety of mechanisms to navigate, including the stars, the sun, olfactory (chemical) cues, internal circadian rhythms that change in response to the seasons, and Earth’s magnetic field (which is shifting more dramatically due to ice melt in the arctic).
Some species may learn their migration routes by first traveling with experienced individuals, but other species are able to migrate without prior experience, an ability that still baffles the scientific community and keeps me mindful of controversial field theory as a possible partial explanation for successful patterned migration.
The latter postulates that each animal has access to its own biological/morphic (family) field and can tap into that field for information and guidance. This theory might help explain why some animals are able to navigate thousands of miles without direct parental assistance. Migration requires a lot of energy and many individuals die during migration. Despite these heavy costs, the potential benefits of migration are great, which is why migration behavior has evolved in so many species.
Approximately 1,800 of the world’s 10,000 birds migrate each year. Many of these migrations are north-south, with species feeding and breeding in high northern latitudes in the summer, and moving some hundreds or thousands of miles south for the winter. However, it must be mentioned that some birds begin to migrate before food supplies even decline, suggesting that seasonal changes in day light or some innate and/or evolving mechanism tells the birds that it’s time to leave.
The shifting range of the Sandhill cranes makes me particularly curious because it seems to be related to Climate Change/global warming. These birds once migrated into Mexico each winter. Now some populations only fly as far south as Tennessee and other south –eastern states, and others remain in Florida throughout the year.
Every spring 400,000 to 600,000 Sandhill cranes—80 percent of all the cranes on the planet—congregate along an 80-mile stretch of the central Platte River in Nebraska, to fatten up on grain in preparation for the remainder of their journey to Siberian, arctic and subarctic nesting grounds. This migration used to begin in mid-February and end in mid-April but for the last two years the birds have begun arriving in Nebraska earlier than ever before. The cranes have also been spotted in western and southern Maine during the spring since the year 2000.
Sandhill Cranes have been in their present form for 30 million years. They have a life span of 35 years and are slow to reproduce delaying breeding from two to eight years so population growth is slow (0.3 chicks actually survive the first year). Fortunately, people have been captivated by the migrations of these magnificent birds so a few sanctuaries have been established to help the species survive. A slow reproductive rate has been a key obstacle to conservation and ‘management’ of the species, keeping these birds at risk.
Sandhill Cranes hold an important place in art throughout the world figuring in traditional Japanese and American Indigenous peoples art where their mesmerizing dances and graceful postures find their way into Native weavings, paintings and dances as well as appearing in contemporary culture.
This winter Abiquiu has been graced with flocks of Sandhill Cranes who have stayed for the whole season, much to my joy and delight. Although, I understand that some cranes have wintered here in previous years at least three big flocks have been flying overhead and roosting down below my house on the other side of the river since late November making me appreciative of the possible short term positive consequences of Climate Change.
We may not know how migration works, but we do know the patterns of migration are changing and that Climate Change is a reality. My fervent hope is that somehow most species, who are all our “elders” – humans, after all have only been around for 200,000 years – (plants for 450 million years, animals for 350 million years) – may possess strategies that we can’t even imagine to survive the damage that we have brought upon all living things including ourselves.