Do you ever wonder where you stored the jar of olives in the pantry, the frozen pheasant in the freezer or the can of sardines in the cupboard? Do you know what strange cultures are lurking in the back of the refrigerator?
We keep a running inventory of stores for our boat on a computer spreadsheet. That saves a lot of head-scratching about what we have on board, where it’s stored and makes preparing grocery lists for future voyages easier. Although we don’t keep a computerized inventory of stores at home, it’s not too hard to find food items because we are familiar with the contents of our pantry, freezers and refrigerator. We must have brains like birds.
During the recent cold spell, black capped chickadees were feeding voraciously at the feeder in front of our house. We feed the wild birds oil seed sunflowers, unsalted peanuts, Niger thistle seed and suet. These seeds are high in carbohydrates and fat that help the birds stay warm in winter. Many of the birds weren’t actually feeding; they were flying away with seeds to store and eat later.
This hoarding or caching behavior is common in many species of birds and mammals. Caching is an adaptation to seasonal changes in availability of food, providing a significant survival advantage. Chickadees take seeds from bird feeders, fly off and stash them under bark or in cracks in the trees. Research biologists have found that individual chickadees can store thousands of food items each year across a wide territory and they do not re-use their cache sites. They can remember the locations of cache sites for weeks. Chickadees use visual and spatial cues to recall the locations of their food caches.
Blue jays, nuthatches, downy, hairy and red-bellied woodpeckers also frequent the feeder and take away seeds to cache for future eating. Blue jays are piggish at the feeder, filling their throat pouches with dozens of sunflower seeds before they fly off.
The brains of winter birds that cache food actually grow bigger in the fall when they start storing food. The hippocampus, the part of the brain responsible for memory, increases in size in the fall and then decreases in the spring.
Winter resident birds have also adapted to short daylight and cold winter conditions in some fascinating physiological ways. Wintering songbirds have higher metabolic rates in winter than in summer. Chickadees maintain a 107°F daytime body temperature and a heart rate of over 500 beats per minute. They eat about 20 times more each day in winter than in summer. On a below zero day, a chickadee can eat 250 sunflower seeds, so keep the feeder filled.
Chickadees often huddle together in tree cavities to keep warm overnight. They really ‘chill out’ at night as their body temperature and heart rate goes down to conserve energy. They wake up in the morning by shivering until they are warm enough to fly.
Seeing all those birds at the feeder makes me think of becoming a south-migrating snowbird again. We look forward to warm blue water, sand, palm trees and frigate birds soaring in the trade winds. Friends can stay at our place and keep the birds fed. Now where did I store the mask and snorkel?
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–Dan Wilcox, outdoor columnist