Here's some news that will justify your corvid love. A new research project in Hawaii, described in a recent issue of Nature, has revealed that crows throughout the world are capable of evolving tool use under the right environmental circumstances. Zoologist Christian Rutz has worked for years with crows on the Pacific island of New Caledonia, who routinely use specially-crafted sticks and serrated leaf edges to retrieve bugs and larvae from hard-to-reach spots in logs. Though Rutz and his colleagues speculated that other crows must use tools, there were no recorded observations of the practice. Until now.

Rutz and a team of researchers worked with a group of 104 'Alalā, or Hawaiian crows and discovered that they used sticks in ways that are very similar to New Caledonian crows. Though the two species are not closely related, they have a few traits in common. Both have long, straight beaks and eyes that are very mobile, which the researchers believe make them particularly adept at using their beaks to guide sticks. To grab a tasty grub out of a log, a crow has to find a stick of the right length, smooth it by removing bark or branches, and then thread it into a small opening to root around and yank out the unlucky invertebrate. 'Alalā and New Caledonian crows also share similar ecosystems: both are island birds, who live in areas with few predators. Unfortunately, human disturbances in the Hawaiian environment have driven 'Alalā extinct in the wild. Rutz and his team worked with birds who live in two different enclosures on the Big Island, using a special "testing log" full of nooks and crannies, to see how they used tools to get at food.

One question is whether 'Alalā learn to use tools from their families, or start using tools spontaneously. The latter would suggest that tool use is essentially a heritable behavior, passed down through genetics rather than socialization. To find out, the researchers reared 7 'Alalā in an enclosure without adults. Within months, all of them began to use sticks to retrieve food. Though adult 'Alalā no doubt help their young learn the best ways to prepare and find sticks, it's clear that this isn't exclusively a learned behavior. The birds will do it even without any training. Because 'Alalā and New Caledonian crows are so distantly related, their tool use is a clear example of convergent evolution, where similar traits arise in two unrelated populations.

Does this mean that only 'Alalā and New Caledonian crows will ever use tools? Rutz and his colleagues say there is ample evidence to the contrary, including the examples of captive birds who are trained to use tools by humans. Indeed, more wild crows might spontaneously start using tools if they were in the right environments. In a previous paper on how tool use might have evolved in New Caledonian crows, Lutz and James St. Claire explain:

The presence of profitable but out-of-reach food, in combination with a lack of direct competition for these resources, resulted in a vacant woodpecker-like niche. Crows may have possessed certain behavioural and/or morphological features upon their arrival that predisposed them to express tool-use rather than specialised prey-excavation behaviour, although it is possible that woodpecker-like foraging preceded tool use. Low levels of predation risk may have further facilitated tool-use behaviour, by allowing greater expenditure of time and energy on object interaction and exploration, as well as the evolution of a ‘slow’ life-history, in which prolonged juvenile development enables acquisition of complex behaviours.

In other words, there were a number of advantages to evolving tool use. First, there were tasty insects and larvae living just out of reach of their beaks, and no other animals were eating them. Plus, the crows had few predators, which gave them time to develop new strategies for acquiring food. They could prepare and test sticks at their leisure, without worrying that a predator might be sneaking up behind them.

'Alalā and New Caledonian crows developed tool use for many reasons, including body morphology and island life in relatively predator-free ecosystems. But in the right circumstances, other crows may follow suit. As the researchers admit, there may be wild crows using tools already, unobserved by scientists. We have a lot more to learn about these highly intelligent corvids, who may be descendent from dinosaurs but share more with humans than we realize.

Nature, 2016. DOI: 10.1038/nature19103