Memory MAESTRO
Despite the rather derogatory term ‘bird brain’, in recent decades we’ve realised that many species of birds display signs of a well-developed intelligence
It’s always difficult to assess intelligence in other species, as we assume (wrongly) that intelligence can only be measured by our own experience of it. But one aspect of intelligence in other species that we can understand is memory, the ability to remember things.
Many species of birds have been shown to have prodigious memories. Some are famous for it. The Jay, for example, is well known for being able to remember where it stored acorns in the autumn. But there is another British bird that has an equally good memory – it just doesn’t get the recognition for it.
The Marsh Tit is a bird that may be fairly familiar to you. They are an occasional visitor to gardens, especially in the south and east of the country, and are fairly well spread around broadleaf woodland in other parts of England and Wales. Probably the most well-known fact concerning Marsh Tits is how similar they are to the much scarcer Willow Tit, but what they should be famous for is being particularly well endowed in the brain department.
Marsh Tits are small birds, but they have large brains, especially when compared with other, more familiar, members of the tit family.
The hippocampus is a part of the brain that all vertebrates have, and the Marsh
Tit’s is a third bigger in actual size than that of the Great Tit, despite the fact that the Great Tit is almost a third larger overall than the
Marsh Tit, and weighs almost two-thirds more than its smaller, maller, but much brainier, relative.
So why is it that the Marsh Tit has such a well-developed hippocampus compared with its larger close relative? It all comes down to food, but it isn’t about what the Marsh Tit eats, it’s all about what it does with the food once it has found it.
Forward planning
The hippocampus is the part of the brain that consolidates information into memory – in other words, it is the part of the brain that remembers things. Marsh Tits feed on a wide range of invertebrates, but, during the autumn, they also feed on seeds and have a particular fondness for Beech mast (or, in some cases, sunflower seeds from garden feeders).
Seeds like Beech mast become available in abundance during the autumn, but only for a relatively short period of time, so to maximise this food source, the Marsh Tit caches the seeds.
It is in effect stocking up its larder ahead of the leaner times to come in the winter. It’s not quite panic-buying, but it is certainly making the most of the opportunity that the autumnal glut of seed provides.
One research team watched Marsh Tits feeding on Beech mast in the autumn. For every one they ate there and then, they would fly off and cache another two. In a little more than an hour, one bird had cached 100 seeds.
Intelligence or instinct?
Now, it could be argued that caching food shows forward planning and therefore intelligence, but it can be equally argued that caching food is an innate strategy – i.e. it is instinctive and this instinct becomes the norm in a population, because those birds that cache food are more likely to survive a hard winter and put their genes into the next generation, and so on. Proving that something is intelligence rather than instinct can be very difficult.
However, it is one thing to cache food, and it’s another to remember where that food is cached, so that it can be successfully retrieved at a later date. Memory recall is not an instinct, it’s a sign of intelligence, and the Marsh
Tit demonstrates this in abundance.
When caching the seed, a Marsh Tit is also very aware of being watched by other birds, especially by other Marsh Tits, and it seems to be aware that the seed they are caching is at risk of being stolen by others.
It therefore takes great care when storing the seed, tending to fly indirectly to where it wants to cache the seed rather than flying there directly. By making several stops on the way, any watching birds are likely to be confused as to where the seed is actually located. This is behaviour that, to me at least, indicates that the bird is thinking carefully about what it is doing.
Marsh Tits tend to store seeds individually, avoiding the old cliché of putting all the eggs in one basket, and when they come to retrieve the seed days, weeks or even months later, they fly to the specific place the seed was stored rather than to the rough area it was hidden in. They remember the exact location rather than a vague area and it is thought that
WHEN CACHING THE SEED, A MARSH TIT IS ALSO VERY AWARE OF BEING WATCHED BY OTHER BIRDS, ESPECIALLY BY OTHER MARSH TITS...
they do so by using visual clues, using ‘landmarks’ to help memorise the cached seed’s location.
So far, so impressive. But not only do they remember where they buried the seed, they also remember when they buried it as well.
Pub quiz champion
When these little birds come to retrieve the seed they cached, they retrieve the oldest seeds first. This is important – the longer a seed is hidden for, the greater the chance that it may start to decompose or even germinate, and therefore it makes sense that they retrieve seeds they stored weeks ago rather than the seeds they cached just a few days back.
Just think about that for a minute – that’s an incredible feat of memory for a small bird that weighs about the same as a £2 coin.
Can you imagine hiding hundreds of sunflower seeds individually over several days in your garden and your neighbour’s garden, and then going back a few weeks later to not only find the seeds, but also find them in the order in which you hid them? Ignoring the fact that your neighbour might question your sanity, I think it is fair to say that this memory feat would be completely beyond us.
Not every bird caches food, of course, but those that do have to have a good memory in order for the strategy to pay off. The reason the Great Tit has a much smaller brain than the Marsh Tit, despite being so much bigger than it, is simply because the Great Tit doesn’t cache food and as a result doesn’t have a well-developed hippocampus capable of remembering locations and timings. Now, I’m not saying that the Great Tit is stupid, but if you were forming an avian pub quiz team, you’d want a Marsh Tit on it over a Great Tit every time!