A drop-catch game sequence

A caught a short clip of a young Herring Gull playing drop-catch today at a local nature reserve. The gull carried on for quite a while dropping and catching the item.

via GIPHY

Social play in gulls?

Yesterday, the pond at my local park was almost completely iced over. While the ducks and geese kept to a small ice-free patch, the gulls seem to like walking on ice. A few young Common Gulls were about. One of them, a second winter bird, was carrying and handling (or should I say 'billing'?) a piece of moss. She would drop it, pick it up, shake it. She was being followed at close range by another two younger first winter common gulls. The first one eventually dropped the moss and one of the younger gulls swiftly picked it up and carried it for a while, in a repetition of the sequence. Then this gull found a short stick and she pecked it and picked it up repeatedly. I was pleased to get this sequence in video.


I have anecdotally documented play in gulls since Ralph Hancock drew my attention to this behaviour in his blog. Play has been described in gulls before, but only solitary play. But, was the behaviour I watched social object play?  According to Judy Diamond and Alan Bond, in a review on social play in birds (where gulls are not mentioned) state:

'Social object play occurs when two or more individuals engage in repeated interaction with one or more inanimate objects in the environment without subsequent consummatory behavior. The best evidence of social object play is provided by contests over items that cannot be otherwise turned to useful purposes. Role reversals are common in social object play, and the interaction often ends with the contested item simply being discarded.'

I believe that the sequence I watched fits this description quite well. The gulls respond to one another in which the 'carrier' changes direction to avoid the 'chaser' and the chaser follows the carrier paying attention to what it does and is quick to retrieve the object when dropped. The interaction ends when the item is discarded. The interest in the moss by the second individual is affected by the carriers interest in it, like the object is given a new meaning as a 'toy'. Much evidence on social play in birds is anecdotal, which a few exceptions, notably in Keas and Ravens. However, given how social gulls are, and how opportunistic, with much adult behaviour involving stealing food items from each other, it appears surprising social play hasn't described in gulls. Possibly casual watchers of distant gulls assume food objects being the centre of attention instead of inedible 'toys'. The park's wintering flock is well used to people and allow close approximation, so it is easy to check what the gulls are handling. I should definitely pay more attention in the future to potential play sequences.

For more posts at The Rattling Crow on play in birds click here.

More information

Diamond, J., & Bond, A. B. (2003). A comparative analysis of social play in birds. Behaviour, 140(8), 1091-1115.

Playing herring gulls

This morning at a local park, I noticed a young Herring Gull picking an object, flying off and being chased by another. Then the gull landed on the water and dropped the object and pretended to dive to pick it up repeatedly, as in a lazy drop-catch game. When I saw the object at a better angle I realised it was an empty freshwater mussel shell, which happened to float. Funnily enough, a couple of hours later when I walked past either another or the same young Herring Gull was still playing with it.

The young gull flies off with the freshwater mussel shell.

Later on, with cloudy weather, two gulls handling the shell.

Play in gulls

I usually check for ringed Common Gulls in my local park. Yesterday the flock, about a hundred strong, converged around someone providing food. While I was checking, a boy run towards the gulls flushing them. A few settled on a puddle nearby, and a second winter one was ringed! I approached and took some photos to try and see the code. No luck, the light was wrong and the gull too active. I decided a video could work as I might be able to get a sharp screen-grab. The gull found a pink object (visible on the left side on the photo above) and started to pick it up and drop it repeatedly, the object bobbed up on the water every time and the gull seemed quite interested, until, after a while, it walked away. I had ended up recording a session of gull play behaviour! I walked away and then thought I wanted to check the object, just in case it was some food item, but no, it was a spongy piece of plastic, probably torn from a soft ball. You can watch the clip here:

 I had never thought gulls played until I started following Ralph Hancock's wonderful blog on the birds on his daily walk around Hyde Park and Kensington Gardens. He describes and documents gulls (Herring, Common and Black-headed) playing drop-catch with various objects: sticks, leaves, plane tree seed heads, rubbish, and stones, and his observations made me pay more attention. He also pointed to this photo sequence of a young gull playing drop-catch.
 How can we know that a particular behaviour is play? Usually play is invoked when a behaviour appears to serve no adaptive purpose. Jennifer Gamble and Daniel Cristol, from the College of William and Mary, Virginia, studied drop-catch behaviour in Herring gulls to discount alternative hypothesis to play. Their Herring Gull population often dropped clams they find on the mud flats at low tide over hard substrates - a tarmac road nearby - to break the shells and eat them. Could drop-catch serve be a practical behaviour? They tested two alternative explanations: the 'kleptoparasite hypothesis' where drop-catch behaviour could allow a gull to asses the chances that other gulls that might be nearby, be ready to steal the clam as it hit the ground, or the 'reposition hypothesis' where the gull might drop the clam and then catch it to reposition it before a proper drop. In contrast, if drop-catch is a play behaviour they expected:
1) It would be carried out more frequently by juveniles.
2) Objects other than clams would be used.
3) It would be performed over soft substrates.
Their results rejected the alternative hypothesis and fitted the predictions of the play hypothesis: younger gulls engaged in more drop-catching than older gulls, that drop-catching was more commonly done over soft surfaces (the mud flats, as opposed to the road and gulls were less likely to drop-catch a clam (9%) than a non-clam object (62%). The conditions at which drop-catch happened were also more favourable to play behaviour: Drop-catch happened more often at warmer temperatures (when the gulls are less cold-stressed) and when wind was stronger (and flight is less costly).
 Play has been much less studied in birds than in mammals, and most of the research in birds has been done with corvids. Gulls are quite opportunistic, long-lived species and play could potentially have long-term beneficial consequences: perfecting the development of the coordinated flight behaviour required to succeed in kleptoparasitic attacks (gull often chase other gulls carrying food and if the attacked gull drops the food, individuals able to catch the dropped object in the air might have a higher chance of success of catching it first) or possibly practice the clam dropping behaviour.
 I have kept the bit of pink plastic, but I haven't yet managed to read the code on the ring, it starts by JP...

More information
Gamble, J. R. & Cristol, D. A. Drop-catch behaviour is play in Herring gulls, Larus argentatus. Animal Behaviour 63, 339–345 (2002). Here.

The variable Redpoll

Redpolls are small finches with a tiny bill, a crimson spot on the forehead and a little black bib and mask giving them slanted-looking eyes. Their plumage is so dense that on their faces it can partially hide their bill, giving them a flat face. They are found from the Arctic (where they are resident), to subarctic and temperate open forest and scrub and specialise on small seeds, mainly from birch, but also alder, willow, spruce, larch (above) and pine cones. They will also feed on various wildflower seeds near the ground.
 Redpolls are very entertaining to watch as they feed, as they reach catkins and cones using acrobatic, agile movements, reminiscent of tits. In addition, they can use one foot to hold onto a stem, a bunch of seeds or catkin to reach the seeds more easily, like goldfinches. They can apparently store up to 2 g of seeds in a expandable pouch in their throat, to eat later in less exposed conditions. Redpolls have been seen 'bathing' and burrowing tunnels in the snow. These tunnels have unclear function, as they don't appear to use them to shelter from low temperatures, rather, they appear to fulfill a social role, or just be a form of play.
  Redpoll flocks have erratic, nomadic, movements in winter in search of seeds, often travelling in the company of Siskins. They also have 'irruption years', following failures on the seed crops on which they rely, or high population densities after a good crop year, often spurred by cold weather. One of the largest irruption years were in the winter of 1995-96, where Arctic and Common Redpolls arrived in the UK in good numbers.
 The taxonomy of Redpolls has been very fluid, with three species, Arctic, Common and Lesser -each with various described geographic subspecies- recognised, but at some point six were described. The browner, small and very streaked 'Lesser Redpoll' breeds in the UK. Diagnosis was based on the lightness and amount of streaking in the plumage and also bill shape and size and overall size. However identification is often difficult, as there is a lot of variation, and many individuals would fall in between the 'classic' species descriptions, resulting 'in much collective head-scratching' in the words of Riddington and colleagues.
  A recent study by Nicholas Mason and Scott Taylor from Cornell University, sampled 77 Redpolls from around their distribution range and looked at the diversity across their genomes, niche differentiation, morphological diversity and gene expression patterns. Surprisingly, all Redpolls were extremely similar genetically, with barely any genomic differentiation between 'species'. The different colour patterns and bill shape can be explained by different gene expression patterns (e.g in response to temperature), but the authors did not find a clear-cut morphological differentiation between species, as many individuals were intermediate. Although recent adaptation to particular local conditions, for example the dominant available seeds) might have happened, it is likely that the nomadic migratory movements of Redpolls result in a lot of dispersal and gene flow between populations and incipient regional varieties, preventing differentiation and subsequent speciation. Perhaps we should just enjoy Redpolls as a delightful bird on its own, and worry less about tidying individuals away into imaginary boxes.

More information
The Cornell Lab of Ornithology Cool Redpoll Facts.

Riddington, R., Votier, S. C., & Steele, J. (2000). The influx of redpolls into Western Europe, 1995/96. British Birds, 93: 59-67. Pdf here.

Gustave Axelson (2015) From Many, One: How Many Species Of Redpolls Are There? Commentary on Mason and Taylor paper on the The Cornell Lab of Ornithology blog.

Mason, N.A. and Taylor, S.A., 2015. Differentially expressed genes match bill morphology and plumage despite largely undifferentiated genomes in a Holarctic songbird. Molecular ecology, 24: 3009–3025. Here.

Collins, J. E., & Peterson, J. M. (2003). Snow burrowing by Common Redpolls (Carduelis flammea). The Kingbird, 53, 13-22. Here.

A male Redpoll feeding on Alder catkins

A Redpoll feeding on Rosebay Willowherb.

A male Redpoll on Alder

An individual on Alder, illustrating their ability to hang upside down from thin branches.

Gulls playing helter skelter?

Do birds play? You have probably seen videos of crows sliding down snow and rolling down on car windscreens, or heard of the Australian black swans that enjoy surfing. These cases, and many others documented for a long time, are hard to explain in utilitarian terms (no feeding, or mating or predator avoidance is involved), it appears purposeless, and seem most fitting to actual play. Play behaviour, often solitary, some times involving objects, but also social, has been described in ten orders of birds including corvids, raptors and parrots amongst others. Some of this behaviour involve play flying, or flying in aerobatic ways. This afternoon, in the first mild sunny day of spring, thermals developed over the park, and a large mixed flock of gulls - Herring, Common, Lesser Black backed and at least a black-headed, later joined by a Carrion Crow - started to soar higher and higher, I could barely see them as they circled. My camera decided to run out of battery run out just at the same time (the photo above is the flock flying high this mid February).
 Then I noticed some gulls tumbling down. Not just gliding, but actually flipping over and going on their backs as they descended. Two of them seemed to be flying together, making a downward double spiral, opposite each other, occasionally tumbling. The Carrion Crow also dropped height by closing its wings as if enjoying the feeling of being kept up by the thermal. It was an exhilarating spectacle to watch, and the gulls gave the impression to be having a good time.