Jays and acorns

A few weeks ago, on a local urban walk, I had the chance of watching some Jays collecting acorns from the oaks. It's been a good mast year and the veteran oaks at the cemetery were laden with acorns. Jays are a scarce and shy species in my city, but occasionally I come across them in the most wooded green spaces. These individuals, at least two, were collecting acorns, flying back and forth from the tree to their larder, a site out of sight beyond the road. Before disappearing into the foliage of the still green oak, they often paused on trees nearby, which is how I took the photo below, the wind pushing the Jay's crest up.

Caching behaviour

Jays are omnivorous and opportunistic in their food habits, but during autumn they become dedicated food hoarders. They are resident birds that depend on their stored harvest to survive the winter and early spring, and are acorn specialists. They have a pouch under their tongues and can carry up to nine acorns in a single trip, although in 80% of trips they will carry one or two. Their acorn reserves will be scattered, a single acorn buried in a shallow hole in the ground, around their home range, and the reserves will be steadily used. You might see Jays in small parties - often detected by their screeching calls -  but they tend to be mindful before they bury each acorn, away from the prying eyes and ears from other Jays, which will be all too happy to pilfer other individual's hoards. Experiments by Nicola Clayton's group have shown that their caching behaviour is dependent of potential pilferers being around and they will cache preferentially behind an opaque screen when other individual is watching, if they are within earshot of other individual, they will cache in quieter substrates (sand) rather than noisy gravel.

Oak foresters

Jays can store several thousand acorns per year, and rely on their spatial memory skills to retrieve them.  They have a mutualistic relationship with oaks, being crucial dispersers of acorns. As not all acorns will be consumed by jays, oak long-distance dispersal depends mainly on Jays, and the forgotten or unused acorns are perfectly planted to successfully germinate. The dispersal distance,estimated using radiotransmitters inserted in acorns provided to Jays in feeders in the landscape ranged from a few meters up to about half a km.

A Jay with an acorn it has just retrieved. It took about minute to find it. Watch the full clip here:

Complex cognitive abilities

It is striking that Jays manage to remember the location of thousands of caches. As other caching birds, they have excellent spatial memory, and perform very well in spatial memory tasks. Experiments have also shown they have episodic memory, an ability to recall specific events and details, both when caching and when pilfering. They might also prefer to cache near vertical structures, which might facilitate recall.

Jay with peanut. Jays are part of the bird community of towns and cities, particularly when tree cover and food resources (oaks or bird feeders) are available. 

More information

Kurek, P., Dobrowolska, D. and Wiatrowska, B., 2019. Dispersal distance and burial mode of acorns in Eurasian Jays Garrulus glandarius in European temperate forests. Acta Ornithologica, 53(2), pp.155-162.

Legg, E. W. & Clayton, N. S. Eurasian jays (Garrulus glandarius) conceal caches from onlookers. Anim. Cogn. 17, 1223–1226 (2014).

Madge, S. and G. M. Kirwan (2024). Eurasian Jay (Garrulus glandarius), version 3.0. In Birds of the World (B. K. Keeney, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.eurjay1.03

Pons, J. & Pausas, J. G. Acorn dispersal estimated by radio-tracking. Oecologia 153, 903–911 (2007).

Shaw, R. C. & Clayton, N. S. Careful cachers and prying pilferers: Eurasian jays (Garrulus glandarius) limit auditory information available to competitors. Proc. Biol. Sci. 280, 20122238 (2013).