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Can gulls get drunk on ants?

Posted by on July 22, 2013

Black-headed gull on flying ant dayRebecca Nesbit from the Society of Biology has been working on the flying ant survey

On Friday I received a phone call asking ‘are seagulls in Devon acting weirdly because of flying ants?’. The answer was very likely yes – flying ant day is a special day for gulls, and for many people the excited squawking of feasting gulls is the first sign of flying ant day.

The next question, however, was ‘could seagulls be made delirious by formic acid from the ants?’.  Gulls have apparently been hit by cars because they are ‘stupefied’ and wandering onto roads.

The popular press are answering this second question in increasingly dramatic ways: gulls are made ‘yobbish’ by ants apparently!  But the real answer has to be the scientist’s favourite of ‘maybe’.

I haven’t found any studies confirming that formic acid is causing the gulls’ behaviour, but we do know that Lasius niger (the black garden ant, responsible for most of the flying ant emergences we see) can produce formic acid.

Other possibilities include the heat, lack of awareness of the road because they are busy eating the ants, or just that gulls have become more noticeable. Delirious gulls are sometimes suffering from lead poisoning, or have botulism from drinking stagnant water, rotten food stuffs or maggots feeding on rotten things.

If we’re going to draw any conclusions about the effect of flying ants on gulls, we will have to study it in more detail. This could mean collecting more observations, finding out how much formic acid is in flying L. niger and seeing whether the ‘stupefied’ gulls recover when they cool down, or when they are no longer eating flying ants. It’s worth noting that some ant species produce more formic acid than others.

A relevant observation is that some birds are well known to use formic acid to kill parasites from ants, in a process called ‘anting’. They will sometimes eat the ants (and hence formic acid) at the same time, though anting perhaps also performs the role of reducing the formic acid birds ingest.

This discussion raised two interesting points which are central to lots of scientific investigations. Firstly ‘correlation does not mean causation’. It could just be chance that ‘delirious gulls’ are being sighted at the same time as flying ants, or it could be that the weather conditions chosen by the ants are causing this behaviour in the gulls.

The second is that absence of evidence does not mean evidence of absence. Just because I haven’t been able to find reliable evidence about the link between formic acid and the gull’s behaviour, it doesn’t mean that this isn’t happening. So, if you see gulls acting strangely, whether or not there are ants around, please add your information to the comments below!

I will also take this opportunity to explain why I dislike the word seagull. There are many different species of gull, from the bolshie great-black backed gull which loves to eat chicks, to the elegant ivory gull. They are all gulls, but not always found by the sea!

17 Responses to Can gulls get drunk on ants?

  1. John Hamilton

    I’ve noticed three pigeons run over by cars on my road – very unusual. On the 1st August, there were many flying ants and I think this unusual behaviour is definitely linked. Pissed pigeons.

    • Rebecca Nesbit

      Actually, wood pigeons feed mostly on seeds, grain and crops so this is less likely to be caused by ants

  2. Julian Green

    If the gulls do get “drunk”, I think this is more to do with a feeding frenzy on the day the ants fly. Green woodpeckers feed on ants all the time. Do they get drunk? I doubt it. Then again, I suppose you could argue that the woodpeckers are used to the formic acid and the gulls are not.

    • Rebecca Nesbit

      If someone put a pile of cake next to the road, I wouldn’t get drunk but I certainly wouldn’t be paying sufficient attention to the traffic…

  3. Gill Vance

    Hi Rebecca,

    This is interesting. I have been looking into the gull research available albeit not in great depth. As we seem to have many sightings of gulls being at literally the centre of the action where flying ants are concerned….how do the gulls know when the ants are liable to be ‘coming out.’ If at all they do know. There are various thesis surrounding the events of ants coming out on flying ant day due to weather pressure drops etc….would the gulls have any inclination of when this would be? I have seen no evidence as yet of any correlation but it just seems odd that they are in the right place at the right time…..notwithstanding being hit by cars and formic acid of course!

    • dave suttle

      I would think that this behaviour is related to their excellent eyesight and social feeding habits. Sit on a seafront and throw a chip in the air – you know what happens. They are intelligent and long-lived (30yrs+) birds which learn from their parents and peers. In Bath there are a lot of gulls and on the river an interesting behaviour has developed over the last twenty years: A pigeon stands at the water’s edge drinking and is hit from behind by a gull. The pigeon tries to take off but the impact causes it to move forward into the water with it’s wings outstretched. The gull promptly hops on the floating pigeon’s back and prevents further struggle. The gull then starts to eat the (live) pigeon by tearing through its back. Bath’s gulls are also partial to full-grown rats and ducklings- I’ve seen a mother duck ‘bring down’ an attacking gull many times. (The ducklings are programmed to submerge and scatter when attacked but it’s a bit sad sometimes when you count twelve ducklings in a brood one day and only two the next.)
      Regarding the roadkill situation, I opine that the gulls are only just learning to exploit this source of food and are twenty years behind the crows and magpies who have it completely sussed now. Given the rise of urban gull populations over the last half-century I would say that they are only just beginning to ‘spead their wings’ as the ‘war’ on these birds is waged by the LAs. Or perhaps they have just tired of burgers, kebabs and alcohol-laced vomit.

  4. Rebecca Nesbit

    Interesting that there are observations of more gulls hit by cars even with no flying ants. The mammal society used to survey road kill to monitor mammal populations – if we were to look at the effect of ants on gulls (or lots of things on gull populations, or even gull populations themselves) a road death survey could be interesting,

    When the flying ant survey results come out you will be able to work out when flying ants were seen in your area:

    • Denis Murphy

      Hello Rebecca,
      following the comments on gulls & ants I wondered if anyone has ever observed gulls apparently feeding on ants whilst on the wing? For the past three years I have observed odd behaviour from gulls assembling in quite large numbers 20 -30, gently circling above my garden, (in a similar way to vultures!) and appearing to change course suddenly and frequently, to snap at something in the air. This odd behaviour always coincides with huge numbers of flying ants erupting from my garden and neighbouring gardens, but at the height the gulls are flying I cant see what it is they appear to be feeding on, even with binoculars. There is no doubt in my mind that they are all intent on catching and eating something on the wing. They assemble for perhaps 30-40 minutes in particular areas over my garden only when large numbers of ants are flying, so I feel it may not be just a coincidence.
      If anyone else has observed this behaviour I would be very interested to hear form them. Good luck with your research!
      Kind regards
      Denis Murphy C.Biol. M.S B.

      • Rebecca Nesbit

        Hi Denis
        I am sure you are right – they are feeding on flying ants. This has often been seen by others, and the swifts often join in too. It makes you realise how high up the ants are flying!

  5. Charles Davies

    I have recently noticed more seagulls struck by cars in my area, however the flying ants have yet to arrive?

    • the twins

      ITS THE CHEMTRAILS ….. okay the planes… up the sky that are spraying that thick white shit that forms into a frickin cloud ..the seagulls fly up high and eat shit out of it ..and acts confused… drunkish …. goes on roads and gets ran over’s happening here too right now THUNDER BAY ….

  6. stargleam

    Gulls are getting incredibly aggressive and invasive, and seem to be growing larger and larger. (I’m aware of the fact that some types are larger, but even the smaller ones seem to be getting really big.)I must admit to being slightly worried by them. I’ve personally seen one that had killed a large song bird, and it really hesitated before deciding to allow me to walk along the path where it had settled. it was like a battle of wills before it fluttered to the side with its kill. Today, in the park, it struck me that there were far more gulls than ducks. You do feel that they’re taking over at times.