Meet the Nucifraga

The genus Nucifraga includes some corvids that don’t get much attention by the general public, but that are highly, highly important to vast numbers of ecosystems.

The Nucifraga are commonly known as the nutcrackers.  Nucifraga literally means “nut shatterer” in Latin (nux, nucis = nut; frangere = to shatter) and as their name indicates, they specialize in eating nuts, specifically nutritious, high-fat nuts from pine cones.  Nuts aren’t the only thing they eat, but nuts are certainly the bulk of their diets along with invertebrates, small birds, eggs, and a bit of carrion.  The relationship of the nutcracker to the nuts they eat is one of the most fascinating biological mutualisms (a relationship beneficial to both species involved) seen in nature.  In some cases, the trees whose seeds the nutcrackers feed on rely upon the birds to disperse their seeds and plant them.  The planting of these tree species (such as whitebark pines and Asian stone pines) in otherwise cleared areas creates the foundation for colonization of other plant species and the creation of forests.  The story is far more complicated and interesting than what I just typed, but I think corvids and how they effect forest ecology will be relegated to a post of its own.  In the meantime, the Coyot.es Network’s own Chris Clarke wrote an article about the peril of whitebark pines and their corvid partners, “An Ancient Partnership Put in Danger“.

Another amazing attribute of nutcrackers is their memory.  Nutcrackers stay in their home ranges throughout the year, which tend to get a lot of snowfall and reach low temperatures with very little food.  To overcome this they cache (hide and place objects in the ground and crevices) seeds and recover them in the winter in order to make it through the winter.  (This caching behavior is how they plant the trees, mentioned above.)  In order to have enough seeds to survive in the winter they cache tens of thousands of seeds during the summer.  Remarkably, they recover 70-90% of those seeds in the winter.  Just think about that for a minute.  Some nutcrackers cache up to 30,000 seeds and they remember the locations of the caches, which contain 1-3 seeds, so that’s about 15,000 locations.  These caches are made during the summer, so in the winter the snow obscures and changes the landscape. This means the birds have to use various levels of landmarks and triangulation to remember the locations of the caches (sometimes this even requires the birds to completely burrow under the snow to get to the caches), along with toting an impressive long-term memory.  Okay, so they cache food in ~15,000 locations, which are obscured in the winter, and they recover food from ~11,250 locations despite the locations being obscured.  Let that sink in for a minute and think about last time you lost your keys or phone or wallet or anything.

What allows these birds to remember such an astounding amount of cache locations is an enlarged portion of the brain called the hippocampus, which is responsible for spatial memory.  However, their incredible memory comes at a cost.  There is only so much space in the skull for a brain, and only so much energy that can be devoted to brain matter, so other parts of the brain are reduced to compensate for the enlarged hippocampus.  Studies looking at the problem solving capabilities of nutcrackers makes them the dunces of the corvid classroom (to be fair, they are still pretty capable among birds in general).  These birds are memory specialists and they are certainly the champions of their specialty, but I point out their lack of problem solving capabilities because it has serious implications for how we define “smart” or “intelligent” animals.  Certainly in a memory task to “prove” intelligence the nutcrackers would defeat any challenger, but ask them to solve a novel problem and they flounder.  Does the inability to solve novel problems like other corvids make them any less cool?  No, it just makes them really interesting specialists in the family.

So who are the nutcrackers then?  There are three species, with multiple subspecies, all in the genus Nucifraga (as I mentioned above).  Let’s say hello!

Clark’s Nutcracker (Nucifraga columbiana)

Photo of a Clark’s Nutcracker (with bulging sublingual pouch) by Mike Ross, taken in Rocky Mountain National Park, Colorado.

This is the North American species of nutcracker found in the western half of North America from Colorado to the Pacific, from southern British Colombia and Alberta to southern New Mexico and Arizona.  Most studies involving memory and the mutualistic relationship between seed cachers and pine trees have been done with this species.

 

Spotted Nutcracker (Nucifraga caryocatactes)

Photo of a Spotted Nutcracker taken by Paul Cools in Veldhoven, North Brabant Province, Netherlands.

It cracks me up that the species name for these birds means the same thing as the genus name, just in Greek instead of Latin (from karuokataktes where karuon = nut; katagnumito = shatter).  Apparently they are so good at shattering nuts they got named for it twice!

This species has a huge range with 8 subspecies.  Generally the subspecies are divided into two group:, the Northern group, which ranges throughout Europe and Northern Asia to Japan, and the Southern group, which ranges throughout southern China and the Himalayas.

Subspecies of the Northern group, which tend to have more white spotting:

  1. N. c. caryocatactes (the nut shattering, nut shattering, nut shatterer)
  2. N. c. macrorhynchos
  3. N. c. japonica
  4. N. c. rothschildi

Subspecies of the Southern group, which tend to have less spotting/a more brown appearance:

  1. N. c. interdicta
  2. N. c. hemispila
  3. N. c. owstoni
  4. N. c. macella

 

Large-Spotted/Kashmir Nutcracker (Nucifraga multipunctata)

Photo of a Large-Spotted Nutcracker take by Menno Hornman taken in Chitral Gol National Park, Pakistan.

This species used to be a subspecies of Spotted Nutcracker, but has since been deemed its own species.  These birds have a relatively small distribution in the western Himalayan forests of northern India and Pakistan and presumably have similar habits of the other Spotted Nutcrackers, but are sufficiently genetically distinct to warrant being their own species.  They have a lot more, and larger, white spots, giving them a whiter appearance; both their common and species name point out this fact (multipunctata is Latin meaning multi =many and punctatus = spotted).  Ornithologists are extremely creative with naming, clearly.

 

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