A bird’s grocery store is the nearest tree or lake or ground for fruit, insects or water life; water is culled from lakes, pools, puddles, and birdbaths. If the weather turns cold enough to snow and freeze, there’s no luck in the menu department. The same holds true for shelter: If it gets too cold, too snowy, or too sparse for adequate shelter, there’s no way to hunker down. No food and no shelter equal a very short lifespan. They must seek warmer climes.
For humans, seasonal migration is optional. For birds who nest in areas where the weather turns so drastically cold they can no longer find food and shelter, it’s mandatory.
How do birds know when to migrate?
It’s not by watching the Weather Channel. Years – millennia to be exact – have honed birds’ instincts on when to leave their nesting areas in search of survival.
The time to go varies with the birds and with their nesting locales. For example, snow geese -- birds who nest on the Artic tundra and down along Alaska and Canada, will move once in early fall down as far south as the Gulf Coast and New Jersey. Small birds such as warblers could start migrating as early as August.
How far birds migrate depend on where they find their creature comforts. Canada geese typically fly to the Mid-Atlantic States while warblers are known to fly as far as Central America, and often as far south as Ecuador. Last year snowy owls, Arctic Circle birds, wintered on the central New Jersey coast in Sandy Hook and on Liberty Island.
Birds are almost human-like when they travel. They pick their times and their routes. Most migrants travel in flocks, the young seemingly learning the route from their elders. Many types of birds, like warblers and thrushes, travel by night and take advantage of wind currents that will take them on their journeys.
It’s thankless travel. Many arrive at their destinations starving, disoriented, exhausted. Some don’t make it at all, for one reason or another. I’ve found warblers dead on ship decks and on street corners. One year I found a woodcock in the road not far from an Audubon sanctuary, its neck broken after presumably being struck by a car during a low, midnight flight. The little guy was still warm in my hands.
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