Exercising the little grey wildlife-gardening cells

It's raining again as I type, and the forecast says that it won't stop until after dark, which is a shame because after the festive indulgences of the last couple of days, it would have been good to get into the garden.

However, the beauty of this season is that it brings opportunities to engross yourself in a good wildlife book and learn a little more about what you might see in your garden in the year ahead.

My new book of enlightenment to come out of my Christmas stocking is the excellent Atlas of Britain and Ireland's Larger Moths.

Compiled by Butterfly Conservation and Moths Ireland, it takes over 25 million records of moths stretching back to 1741 (although about 18 million are from the digital era since the year 2000) and presents them as maps of dots for each species. These are moth records from volunteers and amateurs across the country ('amateur' of course meaning someone who does it for the love of it).

The immediate thing you can learn from all this data is whether a particular species of moth is likely to turn up in your garden based on whether it is found in your area of the country So, for example, you can see that the Large Yellow Underwing (top left below) is found almost everywhere across the whole country, from the tip of Cornwall to Unst in Shetland. However, unless you live in East Anglia or Hampshire, you are unlikely to see the Lunar Yellow Underwing.

However, the book tells us much more than just distribution. The yellow dots on the maps show where a species used to be but hasn't be found recently, so even on my little thumbnail images above, you can see the Lunar Yellow Underwing used to be found in many more places than it is now. Likewise, the maps show where species have expanded their range.

Given all the worrying news about wildlife declines, it is interesting to see how many larger moth species have increased or declined between 1970 and 2016. Of 390 species, 163 have contracted in range but 227 have expanded. This is the interesting anomaly with climate change - we tend to think of global warming as something that will harm wildlife, but in the British Isles we will see many species extending their distribution northwards, making it look as if things are well. However, what is likely to be the case is that any species expanding its range along its northern edge will probably be contracting along its southern edge, even if that is in mainland Europe.

All this data also allow the calculation of abundance trends, revealing whether there are more or fewer moths of each species. Here, the picture is very different: 248 species have decreased, while 149 species have increased, despite all those species of moth now being able to live much further north than they used to.

The other really useful data shown in the Atlas for all of us in our gardens is the flight season for each moth. So, for the Magpie (below), the little bar chart on the left shows how the flight season is between the end of May and the beginning of September, but most of the records are in July and August where the bars are highest.

It is books like these that allow you to hone your skills at knowing what to expect where and when. There's that old saying in wildlife gardening of 'Build and they will come', which suggests that, if you create a habitat, the intended wildlife will arrive and set up home. However, what major works like this show is that it is actually a more nuanced,  'Build, and they will come if they live nearby, and remember you will only see them at the right times of year'.