The Art of Scatter Hoarding

Andy looks at the cacheing behaviour of Clever Coal Tits at Culag Woods

There is not really a breath of wind but the cold fingers of winter reached into my very core in the woods. I can even taste the freezing air as it enters my lungs. Spring seems far away. Everything is still, except the high pitch calls of many small birds, deep in the Culag woods, outside Lochinver.

Coal Tit - D.Haines

I can make out blue tits and great tits, ducking and diving amongst the birch bark and ivy. A treecreeper makes its way up a gnarled alder tree; long tailed tits repeatedly call to each other as they do acrobatics in the tree tops. I watch them flit cross my path and count them one by one. These dainty birds with their absurdly long tails are one of my favourites.

A goldcrest appears - Europe’s tiniest bird. Some Goldcrests arrive in the Highlands of Scotland from Scandinavia just for the winter, some battling through the 400-mile North Sea crossing in less than 24 hours. But this goldcrest is outnumbered by a band of coal tits as they gather on a tall Scot’s pine tree. The subtle winter-coloured plumage of the coal tits are a perfect match for the surrounding environment. The birds rummage within the needles for insect food, so delicate is their fidgety but precise work.

Anyone who spends a lot of time walking in the winter quickly realises, that contrary to common perception, there can be a lot of birds in some of these tiny pieces of woodland, even in the coldest months. Birds need adequate food sources to stay safe and warm through the long cold season, but when there are no buds, fruits or flowers available, plants are dormant and insects are scarce, what do winter birds eat? While there may not be flying insects in the winter, dormant insects and larvae are a critical food source for birds. Tits, robins, wrens, treecreepers, woodpeckers and other birds will forage in tree bark for insects that provide valuable protein.

Coal Tit - Andy Summers

But finding enough food can be a challenge, especially in poor weather and harsh conditions. So this is why some clever birds have been “caching” food throughout late summer and autumn. They will visit these extra food supplies all winter long. Birds have good memories and can recall where they found exceptional food sources earlier in the year or in previous winters, and they will often revisit the same areas in search of more resources.

And the one delightful little bird that does this caching business really well is the coal tit.

Coal tits (Peripatas Ater) have long toes - ideal for acrobatics high in branches and an extremely narrow bill for teasing out seeds from pine cones. In the otherwise motionless woodland, all these small bundles of feathers, hang on to life in the harshest of days.

In the winter, blue tits often go about in these mixed species flocks; indeed they often form the nucleus of such aggregations. Ringing studies have shown that blue tits come from two different social backgrounds: some are residents, moving around with the flock close to their territory or birthplace; others are nomads, moving from area to area and enjoying only temporary membership of any flock. I find myself wondering where these blue tits have come from.

By grouping together and going systematically through a woodland, birds can save a lot of wasted time and energy searching a patch that has just been searched thoroughly by its neighbour. It makes sense to cooperate. And of course, it is a delight when you suddenly come across one of these mixed species flocks of woodland gymnasts.

Blue Tit: Photo by Yomex Owo on Unsplash

For a coal tit, life can be hard. Being much smaller, coal tits are constantly bullied by blue tits and great tits, which frequently attack them and steal their food. You can see this when you watch birds at the bird table. Where they all live together, coal tits will find themselves literally at the bottom of the tree when it comes to nest sites. Blue or great tits take the safer, higher holes, while coal tits are condemned to whatever they can find, such as mouse holes and crevices among roots.

But coal tits are clever.

When a while coal tit finds a suitable supply of, let’s say, sunflower seeds in a nice persons’ garden, handily available in a lovely hanging tube feeder, it will take a seed and hide it somewhere. Maybe it will hide it in a a crevice in tree bark. It will return time-after-time to do the same thing. When blue tits, great tits and house sparrows are fighting among themselves for a dominant spot on the feeder so they can munch away, a coal tit will nip in as quick as lightening, carry out short commando-style raid, and grab a seed.

Indeed, a small flock of coal tits can empty a whole feeder of back sunflower seeds in less than a day doing just this. And if you didn’t know that the birds were caching the food rather than eating it (though they will of course be eating some in the process to keep energy levels up), then you might be forgiven for thinking that hundreds of them were involved in the sortie on the feeder, rather than the more probable number of half a dozen.

As part of this caching strategy, individual coal tit will use multiple locations to hoard their winter supply of food. This is called ‘scatter hoarding’. This ensures that if another species of bird – e.g. the more dominant Great Tit – finds the food cache, then it will lose only one or two.

Whilst these small birds gather together in winter flocks to improve their chances of finding food and surviving attacks by predators, spring is round the corner. This cooperation will start to break down in the next few weeks as the birds pair up and start to form territories. It is a complete change of strategy. Then the birds will defend an area of woodland from all other birds of the same species. That territory has to be large enough and productive enough to feed a family and the next generation of coal tits.

Climate change and the wildly fluctuating temperatures must be making it harder for birds to predict when Spring has actually arrived.

I know the feeling.

Andy Summers, North Highland's Senior Ranger for High Life Highland, is a dedicated naturalist with a deep understanding of the region's diverse ecosystems. His extensive experience in wildlife conservation and passion for preserving North Highland's pristine landscapes make him a vital asset. Andy's work encompasses wildlife observation, environmental education, and passing on a greater appreciation for the area's unique flora and fauna. His commitment to conserving North Highland's natural heritage is evident in his expertise and unwavering dedication.

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