It's easy for us humans to fish food out of jars with narrow openings. We have things like utensils and opposable thumbs and if all else fails, the ability to turn the jar over. Then, presto! We have that last stubborn pickle.

It's less easy for animals that lack our flatware or thumbs, but that doesn't stop some of them. A wide range of animals are known to use tools, including a few birds — especially certain corvids that are famed for their tool-using abilities.

A 2016 study published in Nature, for example, found the Hawaiian crow (Corvus hawaiiensis) is a crafty tool-user. The crows will turn sticks into skewers to draw out pieces of meat from logs, and they'll even go about seeking out the best stick for the job. If one stick is too short, it gets tossed aside. Too thick? The bird moves on.

Since Hawaiian crows are extinct in the wild (although that may slowly be changing), it would be reasonable to think the birds' tool use might be limited to a certain group of birds that live in their sanctuaries, but that's not the case. Not only did 93 percent of the birds observed use sticks as tools across the preserves, but researchers noted juvenile crows exhibiting tool-using behavior as well, and they did so without any social training from older crows.

Customizing tools all on their own

As the video above points out, Hawaiian crows aren't the only corvids that turn to tool-based solutions. Another tropical crow, the New Caledonian crow (Corvus moneduloides), has long impressed researchers with its excellent use of tools. Not only can it select a good pre-existing twig to use as a tool, but it has been observed manufacturing tools by breaking twigs off bushes and trimming them into the right shape. It's the only non-human animal known to make hooked tools in the wild.

Here's a video, courtesy of a New Caledonian crow wearing a tail-mounted camera:

New Caledonian crows make a variety tools this way, and can develop new tools surprisingly quickly when the need arises. In a 2018 study, researchers found the crows can retrieve food 10 times more quickly with one of their hooked tools than with a simple twig — highlighting a "powerful driver for technological advancement."

"When I see these crows making hooked tools, I have a glimpse of the very foundations of a technology that is evolving," lead author Christian Rutz, a biology professor at the University of St. Andrews, tells the BBC.

Finding innovative ways to build tools

Another 2018 study provides even more evidence of how intelligent Caledonian crows are with building tools. An international team of scientists from the Max Planck Institute for Ornithology and the University of Oxford discovered that the crows can actually build tools by combining two-or-more tools together.

Researchers provided crows with a variety of short instruments that were all too short to reach food inside a box unless they were connected together. Once assembled together, the crows used the longer stick to successfully reach the food. Assembling different pieces together has only been observed in humans and apes before. This study demonstrates just how advanced crows are with problem-solving skills.

Hawaiian and New Caledonian crows evolved in similar environments, but they did so independently of one another, meaning the crows weren't swapping tips on which stick is the best one for the job. Researchers think the birds' similar environments — including a lack of competition and predators — gave them ample time to experiment with tool use.

The same way we figure out whether or not the salad fork works better than the dinner fork for spearing that last pickle.

Editor's note: This story has been updated since it was first published in September 2016.

Clever crows use the best stick for the job
Recent studies shed light on impressive tool use in two species of crows.