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).   

Mute Swans leaving home

There was a news item yesterday regarding a Mute Swan that had crashed through someone's bathroom window. The swan was treated for cuts and taken for further treatment. The photos suggest that this was a young mute swan. What was it doing to crash in such a way?

Young leaving home 

This time of the year young Mute Swans will be leaving their parents' territories, in search of new homes. Cygnets share their parents territory for a few months, but as the parents start preparing for a new breeding season, the male, called 'cob' becomes more and more intolerant of his offspring, busking to them and trying to keep them out of the water. This blog post was prompted by the arrival of a young mute swan to my local patch, which I saw this morning for the first time. It has possibly dispersed from a nearby lake, where they have bred this year.

A newly arrived Mute Swan at the drain today.

Parents vary in their tolerance to immature swans in their territory, or this may depend on the size of the lake, possibly smaller territories may prompt cobs to chase their offspring earlier. One pair in a local park has two batches of young, the oldest were being chased on Saturday out of the water by the cob.

26th December 2020. Adult pair of swans chase their yearling outside the water.

Cob busking to young, followed by the pen.

Fly practice

Swans are one of the largest flying birds. They are also not amazingly manoeuvrable, and collisions (for example with electric lines) are one of the main mortality causes in swans. Taking off involves paddling on the water while flapping wings, they need a clear length of water to do this and then upon starting their flight they will need to fly up so that they clear any obstacles such as trees and houses on their way. 

Mute Swan in flight.

Watching swans in my local area, I've become aware of practice flying in which young and adults participate. This activity may help the young acquire key flight skills, taking off, landing and strengthen their wings  A short chase by the male may end with several members of the family flying along the lake, to land at the other end, but I've also seen lone young practicing when alone. There is a very good description of practice flying in the blog Swan Life.

 

Cob encourages young to fly. I described the behaviour in my Wild at Hull blog on the 8th December:  "As I got to the lake I saw the Mute Swan family gathered on the north edge of the lake. The adult pair had their two yearlings, born in 2019, and three young born in spring 2020. Usually swans chase their young away from their territory in the autumn, but this pair tolerates their young for much longer, probably because of the large size of the lake and plentiful food. The cob, however, was all fluffed wings and lowered head, a behaviour called 'busking' to one of the two older young. After a short chase, the young started flying, followed by a younger sibling and dad, and all three flew to the other end of the lake. I watched this happened three times while I was there. The swans only needed to drift on the wind to the top of the lake, and then take advantage of the gentle head wind for an easier lift. They yearlings might be getting ready to finally leave their natal lake, practicing taking off and landing".

Another clip of the 'practice flight' next. This is not a take off that failed, the trees and the end of the pond make it impossible that the swan would be able to take off in this direction. Practice flying and landing seems to be the motivation behind it. Note the feet propel the swan over water increasing speed and lift, and are also key to brake when landing.

   

More information

Collins, R. Sex Differences in the Movements and Mortality of Mute Swans. Waterbirds: The International Journal of Waterbird Biology 25, 157–161 (2002).

Frost, D. (2008) The use of ‘flight diverters’ reduces mute swan Cygnus olor collision with power lines at Abberton Reservoir, Essex, England. Conservation Evidence 5, 83-91.

Birkhead, M. and C. Perrins (1986) The Mute Swan. 

A story of ringed Mute Swans

Last Wednesday 1st of November I went to Pickering Park. There were six Mute Swans. The resident cob (841 yellow ring), followed by the resident pen (ringed 842, top shot) was busy busking towards a white swan in the lake, who tried to avoid him and ended up preening on the bank at one end. It was a polish variant one, possibly a young of last spring, and when it came out to the shore I could see it was also ringed (red 182Y).
There were also three brown-feathered young swans, starting to moult into adult plumage. Just one of them was ringed (red 537). I assumed they were offspring of the resident pair. One of the brown young kept near the polish one being chased, joining it on the shore.

182Y at Pickering on the 1st of November.

The brown swan accompanying 182Y at Pickering.

The resident pen at Pickering.

***

On Sunday 5th I went to Pearson Park. I was pleasantly surprised to find a mute swan, brown, not ringed. After a while I realised that there was another mute swan, white, on the other side of the pond. The small lake at Pearson Park has very rarely held swans, and not for too long. The last one I saw there was a juvenile from November 2005 to March 2006, when another two appeared in the park before all departed. I casually checked for rings, as I often do, and after some trying I managed to read it. I was surprised to find that the white one was the same that was being chased at Pickering Park, 182Y! The brown young wasn't ringed, but its plumage development is consistent with the one keeping near 182Y at Pickering, so both birds must have left the lake together, possibly an incipient young couple? 

182Y now at Pearson Park. I was able to read the ring as the swan swam.

The brown unringed young at Pearson park.

Both swans at Pearson Park. The white swan showed some aggressiveness towards the brown one, pecking it when it got close.

The swans are getting a lot of attention at Pearson Park. I think the brown one is a male, as it occasionally fluffs up its neck which looks thick in comparison to the other. Still there today, being fed by locals. There is currently a good empty breeding territory at Oak Road lake, it would be good if these two moved there!

Coots settling in the park

I wrote about the visiting coot a few posts ago, but there has been new developments in the local park, a few days ago two coots were present and today I counted three coots. They were quite dispersed in and around the pond, but from a particular location all were visible. If they are just coming in or they have been here all along since I saw the first one, I do not know. They are relatively vocal, appearing to keep in touch with each other. This afternoon, two of them seemed quite content, preening close to each other, while surrounded by playing children and lots of people in the park, they most likely dispersed from another park, where they have grown accustomed to people. Male and female Coots have similar appearance, although males are larger and heavier, so possibly the individual in the foreground on the shot above, much larger, is a male. Male and female, however, have very distinct calls. I hope that at least a pair stays in the park as they will provide opportunities to get to watch them closely and learn more about their behaviour.

One of the coots being chased away by the resident Moorhen (with its nest in the island tree).

Coot about to dive

This is the third coot, note its very large frontal shield, protruding from the top of the head and stained pink. The two individuals at the top of the post have much smaller shields.