Nature Notes: Caching Chickadees

As winter approaches, we are seeing many changes in our bird populations. Some birds, like robins, have formed large flocks and are slowly moving south. Others, like our juncos, have just recently arrived but are only passing through on their journey from northern Canada to southern Minnesota and beyond. Others who will remain here all winter are busily visiting our feeders.

Birds essentially have two options when it comes to winter: they can migrate or they can stay. If they stay, they need a way to stay warm and a way to gSparkyStensaasSnowyOwl.jpget enough food to make it through the harsh winter. Again, they essentially have two options: they can wander widely to find food or they can cache food during times of high food abundance. Owls are a good example of a bird species that stay but wander widely to find food. They have large territories they move around in to search for food. Sometimes, when no food is available, owls will leave their territories and widen their search area. In the last two years, we have witnessed an irruption (a sudden increase) of snowy owls in northern Minnesota as a result of food scarcity in their more northern habitat.

We’ve recently discussed food caching behaviors in mammals like squirrels and beavers. Now let’s take a look at some of our avian friends who store food to prepare for winter. The most notorious hoarders in the Minnesota Northwoods are the chickadees, nuthatches, and jays. In the late fall, you can find these birds at your feeders, grabbing seeds, flying away to store them, and coming back for more. Each species of bird demonstrates different behaviors in how they collect and store food.

Blue jays have a particularly interesting adaptation for food caching. The esophagus in these birds is stretchy creating a gular (throat) pouch, allowing blue jays to gather a lot of food at one time. It’s like a built in shopping bag! Being able to carry numerous seeds per trip greatly increases the hoarding efficiency of blue jays. They can even store multiple acorns in their gular pouch at one time! Watch a blue jay fill its gular pouch!

So where are they taking those seeds? After a blue jay collects its larder, it flies off to hide the seeds for a later date. Blue jays dig holes in the ground with their beaks and bury their treasures individually, topping off each hole with a leaf, stick, or rock. Scientists are not entirely sure why they do this, but they suspect it serves as a visual reminder of the location of their natural pantry. Blue jays are watchful while hiding their food and are keenly aware of prying eyes. Unlike other bird species, there is very little interspecies (within the species) stealing from their caches.

In the more northern regions of our state, there is another type of jay busily storing food. The gray jays have a different strategy for food caching. They live only in very cold climates, working hard throughout the summer to store enough food for winter. In fact, they are one of the only species which raise young in the cold of late winter/early spring (below). Some scientists think this frees up more time in the summer months, when most birds are breeding, to collect the abundance of food available. And they’re not picky.

grayjayon-nest-dan-strickland  grayjay-with-meat

They will eat just about anything including insects, amphibians, small mammals, nestling/small birds, berries, seeds, and carrion. Gray jays collect bits of food and use special sticky saliva to essentially “glue” the seeds to hiding spots behind bark, under lichen, and in pine needles. Not only does this specialized saliva help ensure their hard work isn’t jostled loose and lost before they can retrieve it, but it also helps preserve the food and prevents it from spoiling! How cool is that?!

The nuthatches are also working hard, storing seeds one by one in the crevice of bark (below left) or moss, bark, or snow. But these birds fight a little dirtier. White-breasted nuthatches usually remain with their mate through winter. However, nuthatches are not above stealing from their mate’s store. You’ll often see one approach the feeder, grab a seed, and fly off in one direction and then the mate comes in, grabs a seed, and flies off in the other direction, hoping to store that seed in a secret place their mate won’t see!

cachingdonna  dscn0794

You may also see red-breasted nuthatches (above right)  caching seeds in the winter. These birds may be residents here all year long, or they may come down from further north in search of a good conifer seed crop. Nuthatches and chickadees may flock together during the winter, making it easier to find food sources and keep an eye out for predators. You might see these smaller birds being bullied by the larger blue jays at your feeder.

Last, but not least, you cannot miss the busy chickadees at your winter feeders. There has been a relatively large amount of research done on the food caching behaviors of chickadees. They use their acrobatic skills to gather food from hard to reach places and store it in hundreds of caches throughout their habitat, never using the same cache twice. So how do they know where they put it? Chickadees have absolutely fantastic spatial memories. The hippocampus is the area of the brain responsible for spatial memory. Studies have found in the fall, chickadees go through a period of increased hippocampus neuron development, essentially increasing their spatial memory capacity for winter! They’ve also found birds in colder climates, which may have to rely more heavily on food caching during winter, tend to have a larger hippocampus (and therefore better memory) than their warmer-climate counterparts. Scientists believe chickadees not only remember the locations of their caches, but are capable of remembering which ones they have already eaten, which ones have been eaten by others, and which ones contain their favorite foods! It sounds like a perfect system, right?

Wrong. The big problem for chickadees is their memory only lasts for 28 days! So in order to retrieve food from their caches all winter long, chickadees need to keep moving their food from place to place. This “refreshes” their memories and allows them to recall where that hoard is for another 28 days. No wonder they always seem so busy!

So take a moment this month to get outside and observe these birds in action! This is actually quite easy to do – all you have to do is put some food out for the birds and find a warm, cozy place to watch! Both chickadees and nuthatches will gobble up sunflower seeds. While the jays will also eat these, they would probably prefer a handful of peanuts. You don’t need to buy an expensive bird feeder – there are plenty of cheap options to repurpose or recycle household items and make one yourself!, like the one in the video above! Check out HDT’s Pinterest board if you need a few ideas! So take a few moments to watch the birds this month. Get your kids involved! Make a feeder together and track the behavior of these seed hoarders! See if you can find any of their caches! Make a cup of hot chocolate and observe from the window. Whatever you do, enjoy!

 

 

 

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