No More Migration?

Why do birds migrate? In a word, food. For many species of bird, especially those in temperate climes, their food supply will dwindle, as cold weather sets in. Birds in northern climates, for example, may gorge themselves on insects during the summer, but must head south when cold weather arrives and the insect population plummets. They fly to the tropics, where their insect diet may continue through the winter.

So why not just stay south all year long, where bugs are plentiful? Why migrate back north all that way? For many birds, it's a good idea to exit the tropics for the summer, for at least three reasons: (1) there is more competition for food in the crowded tropical forests, (2) they themselves may become food for predators and parasites whose population will increase, with all those birdy meals flying around, and (3) if they head north for all those plentiful, juicy insects coming out of hibernation, they will find lots of food to make them healthy and give them a netter chance at reproduction.

Birds have migrated for millennia, because the rewards are worth it; despite the fact that it's a risky adventure. Many threats await them en route, such as predators, high winds, cold snaps, habitat degradation by humans, storms, wind turbines, etc.

Recent German studies using tiny GPS tracking transmitters attached to white storks, followed their migration flights south from Europe to wintering grounds in Africa and Asia. The researchers discovered a new development: some of the storks have dramatically altered their migration routes in recent years. Why? In a word, food. What some of these long-range migrating storks have discovered is that they no longer have to endure several-thousand-mile risky flights to find tropical food, because they've located new and plentiful sources of meals along the way. Why fly another thousand miles or so, when they've come upon a plentiful supply, halfway there?

And what are these modern sources of abundant food for the storks? Human-provided massive rubbish dumps and sprawling landfills. These dumps contain oodles of food waste. To add icing on the garbage cake, oodles of insects that thrive on the piles of rotting, discarded food are fine prey. It takes a lot of energy to get a big stork in the air and then to fly several thousand miles. These birds have a wingspan of about five feet (1.5 m) and can weigh about eight pounds (3-4 kg). If, on the way south to its winter feeding grounds, a bird can cut short the exhausting flight and spend the winter on a huge smorgasbord of food waste, why not?

This discovery is a very recent one. It may appear to be a bonanza to the storks, but is this a healthy and sustainable practice? Much of the food is rotting and can contain some pretty nasty microorganisms. Worse, the dumps contain lots of inedible and even toxic wastes—plastics being a major concern. The truncation of their migration flight can have knock-on consequences in the tropical locales the storks no longer reach, when insect pests down south are no longer preyed upon by the storks. Bug numbers might explode, which would negatively impact farms in tropical regions.

These disruptive migration flights of storks are just one of many examples of how humans are altering the environmental balance achieved over millions of years by Mother Nature. When that balance and the tight, interconnected web all these animals are a part of, gets corrupted by humans, the downstream ramifications can be severe. We are messing with ecosystems—complex systems that we hardly understand. It took millions of years to achieve that exquisite balance. We are irreparably disturbing it. How long before it gets back in balance? Can we back off and wait another few million years?