Given the opportunity, some birds can be surprisingly inventive when gathering food. Ornithologists have spotted green herons (Butorides virescens) using bread to lure fish, ravens (Corvus corax) dropping nuts on roads for passing cars to crack, and Barbados bullfinches (Loxigilla barbadensis) taking and pecking open sugar packets from restaurants. One group of birdwatchers even caught rufous treepies (Dendrocitta vagabunda) stealing burning candles from a Hindu temple, only to extinguish the flames and consume the cotton-and-butter wick.
Many ecologists suspect that these unusual behaviors are more than just curiosities—they could be part of a pattern that explains why some species survive while others go extinct. An idea known as the cognitive buffer hypothesis, introduced in the early 1990s, posits that animals capable of coming up with new behaviors are better able to respond to environmental change. According to this idea, bird species that have larger brains and are thus more capable of innovating new foraging techniques have an above-average chance of finding a way to survive if their native forest habitat is disturbed by development of agricultural land or suburbs, for example.
Ecologists suspect that these unusual behaviors are more than just curiosities—they could be part of a pattern that explains why some species survive while others go extinct.
The hypothesis is subject to a few caveats, though. One is that “species that have bigger brains also develop more slowly and reproduce more slowly,” says Trevor Fristoe, an evolutionary biologist at the University of Konstanz in Germany. The large brains that enable some birds to adapt to change could therefore also make it harder for them to recover from a population decline. As a result, Fristoe notes, “we really don’t know [whether] big brains are going to help birds cope with all the ways that humans are changing the planet.”
Wondering whether innovative behavior could help birds avoid extinction was what motivated Louis Lefebvre 25 years ago to start keeping tabs on unusual bird behavior. Every time an ornithologist described a bird species trying a new food or using a novel foraging technique, Lefebvre, an animal behavior researcher at McGill University in Montreal, recorded the innovation.
After more than two decades of monitoring such reports from around the world, the innovation database covered more than 10,000 bird species and documented more than 3,800 behavioral innovations. These include great cormorants (Phalacrocorax carbo) in New Zealand following ferries to catch fish disturbed by the boats’ wake and Carib grackles (Quiscalus lugubris) stealing dry cat food left on porches and softening it by dipping the pellets in puddles. The database also lists innovations that Lefebvre calls a bit more “boring.” For example, if a bird known to eat nine types of seed was observed eating a tenth type of seed, that was registered as a new behavior.
Lefebvre and his former graduate student, Simon Ducatez, now a postdoc at the Ecological and Forestry Applications Research Centre in Barcelona, used the dataset to test whether birds’ propensity for innovation correlated with their risk of extinction, as measured by the International Union for Conservation of Nature (IUCN) Red List. The team’s analysis also controlled for variation in generation time and other key differences among the birds in their database, as well as for the fact that ornithologists are more likely to spot innovations for species that are widespread and more frequently observed.
After accounting for all these factors, Ducatez and Lefebvre found that species that had demonstrated at least one behavioral innovation were generally at a lower risk of extinction than species that had never been observed to innovate at all. Moreover, species with three or more documented innovations were more likely to have increasing populations than species with just one or two new behaviors. “Population declines seem to be happening in species that do not frequently show changes in their feeding behaviors,” says Lefebvre.
Both Ducatez and Lefebvre emphasize that specific innovative behaviors are less important for extinction risk than birds’ capacity to innovate. “It’s not because one specific heron is using bait to catch fish that it’s going to fare better in the face of environmental changes,” Ducatez explains. “It’s the ability to develop new and complex behaviors that would help if it is facing changes in its environment.”
The team found that the relationship between innovation and species survival was driven mainly by data on birds endangered by habitat destruction. Innovativeness was not significantly associated with extinction risk among species that were instead threatened by poaching or invasive species. Just because a species has the propensity to develop new foraging behaviors, Ducatez notes, does not mean that it can also evade new competitors, hunters, or predators.
Sahas Barve, an avian evolutionary ecologist at the Smithsonian Museum of Natural History, cautions that Lefebvre’s database considers innovations at the individual level, rather than the species level. To confirm the link between birds’ innovative capacity and reduced extinction risk, “the next step,” says Barve, is to determine whether “many individuals within those species are innovative.”
Still, Barve was supportive of Ducatez and Lefebvre’s conclusion that the capacity to innovate plays a significant role in the resilience of many bird species to environmental change. The team’s findings also offer a glimpse of the potential future of ornithology. “Maybe in 100 years we’ll be left with crows and herons,” Lefebvre jokes. “Some birds are going to make it through whatever we throw at them.”
Michael Graw is a science writer based in Bellingham, Washington, covering ecology and the environment. He can be reached at firstname.lastname@example.org.