Blue tits (Cyanistes caeruleus) and great tits (Parus major) are small birds commonly found across Europe and parts of Asia. Both species are highly adaptable and thrive in various habitats, including woodlands, gardens, and parks. According to a new study, they also have a remarkably well-developed episodic memory that helps them find food. This was not what the researchers were expecting at all.

Episodic memory is what most people simply call “memory”. It’s the ability to recall past events and experiences, and it was traditionally considered a human-only ability. However, research is showing that we are far from unique when it comes to episodic memory.

Tits and PITs

To study this cognitive ability in the wild, researchers fit 94 wild tits with passive integrative transponder (PIT) tags. PITs are small, implantable devices used for the identification and tracking of animals. These tags contain a microchip with a unique identification code, which can be read by a scanner emitting a low-frequency radio signal.

The researchers then used these devices to monitor how birds manage two tasks.

The first task focused on what-where-when memory, which involves recalling the content, location, and timing of events. Birds learned to associate specific feeders with different food types and temporal availability. For instance, a feeder with preferred food (sunflower seeds) would become inaccessible after a certain period, while less preferred food (peanut pieces) remained available. This setup mimicked natural foraging scenarios, requiring the birds to remember which feeder had what type of food and when it would be available.

The second task examined incidental encoding, the birds’ ability to automatically and unintentionally remember spatial and visual details of their environment while focusing on something else. Feeders were arranged in distinctive spatial patterns (triangle or linear arrays) and marked with unique colors or patterns. Birds had to remember the specific feeder they previously visited to find the food again, testing their incidental memory.

The results were compelling.

In the what-where-when memory test, both blue tits and great tits demonstrated a clear ability to recall the specific details of their foraging experiences. They successfully remembered the type of food, the location of the feeder, and the time elapsed since their last visit. This ability to integrate different types of information is a hallmark of episodic-like memory.

“The birds were behaving naturally in a familiar environment, so we captured something more realistic than if the birds had been captive. It was remarkable to see these birds perform well in our memory tasks while also experiencing a bunch of other memories out in the wild. For us, field research is challenging because the birds are completely free not to take part in our experiments and just fly away, but we’ve shown this type of intelligence test in the wild works,” says Senior author Dr. Gabrielle Davidson from the University of East Anglia said.

In the incidental encoding task, birds also showed remarkable memory capabilities. They were able to recall incidental spatial information about feeder locations. Interestingly, juvenile birds, but not adults, could also remember incidentally encoded visual information, suggesting that younger birds might rely more on visual cues during foraging.

“These findings provide the first evidence for episodic-like memory in the wild and show that blue and great tits have a more flexible memory system than we used to assume,” added first author James Davies, from the University of Cambridge’s Comparative Cognition Lab.

“Previous studies on episodic-like memory have involved bigger-brained bird species like corvids (crows and ravens), which hide food. This study focuses on smaller-brained and more generalist birds that don’t hide their food. Our findings suggest these birds are more intelligent than they’ve been given credit for.”

Not only do the findings shed more light on what was once thought to be a rare ability, but they could force us to rethink the evolution of memory in birds. This memory system might have evolved independently in different lineages to meet similar ecological challenges.

Nicola Clayton, Professor of Comparative Cognition at the University of Cambridge, an author of the study and Davies’ Ph.D. supervisor, said it was fascinating to see these inconspicuous species showing episodic-like memory.

“When I began this research in the late 1990s, most psychologists assumed that the ability to remember the ‘what, where and when’ of unique past events was uniquely human. The initial findings in scrub-jays showed that this was not the case. Subsequent research suggests that this ability is much more widespread in the animal kingdom than we previously thought.”

The next step for the researchers now is to see whether birds with a better memory have enhanced reproductive success. If that is the case, it would indicate that the memory system emerged as an adaptation to challenging environmental conditions.

James Davies et al, Episodic-like memory in wild free-living blue tits and great tits, Current Biology (2024). DOI: 10.1016/j.cub.2024.06.029. www.cell.com/current-biology/f … 0960-9822(24)00813-3