a house of sticks
Perhaps I was a piggywig in a previous life? I have certainly built quite a few houses of sticks recently.
Our gardens create a lot of waste material, and when we've been around with the secateurs and loppers we are frequently left with collections of twigs and sticks. Pile 'em up, is what I say!
In gardening for wildlife we mustn't forget how important it is to see the world from ground level. Bugs of all kinds scuttle or slither around the soil - and piles of sticks can be a great haven for them. If the sticks have begun to decay, that is even better. And if the garden is replete with creepy-crawlies, the next creatures in the food chain will benefit. So, small birds and amphibians will grow fat from the greater food source you have created.
And of course, toads and newts will not only want to go a-hunting around the sticks, they will find lovely damp shelter in there too.