After freezes have turned our tomatoes and beans into sticks, we good gardeners gather up the detritus and do our best to turn it into compost. Traditionally, materials are chopped and piled into layers with manure or finished compost to get things cooking. Water is added along the way in attempt to create a uniformly damp heap that will decompose to a modest degree during the cold winter months.
But there may be a better way to build an end-of-the-season compost pile. A bird nest compost pile is designed to rot from the inside out, with nitrogen-rich materials concentrated in the centre, surrounded by random garden debris, with rougher stuff on the outer edges, like a bird nest.
A bird nest compost has several advantages. Less time is spent chopping materials into small pieces, and it’s easy to maintain a well-dampened, bioactive core. There is no need to turn or mix the heap until spring, after the outer materials have gone fragile and are easy to chop.
![Bird nest compost pile with plastic dinosaurs]()
A whimsical bird nest compost pile built by the Sacramento Master Gardeners. Photo by Janelle Auyueng
History of Bird Nest Compost Piles
The idea of creating a heat-generating compost pile is literally as old as the dinosaurs. Some species were too big to sit on their eggs, so they dug holes, added organic material, and laid their eggs where they would stay uniformly warm from gentle heat generated from the compost. It’s a practice still followed by mallee-fowl and a few other birds in Australia. The males maintain huge compost-lined nests which serve as egg incubators, with temperatures maintained around 93°F (34°C) at all times.
More recently, Master Gardeners in New York hit on the idea of composting like a bird, which involved framing the heap with sticks, and adding finer materials to the center. The idea has since been replicated and refined in ways that help generate and retain geothermal heat by following one of nature’s basic blueprints – the circular bird’s nest.
![Red-eye vireo nest]()
The nest of the red-eyed vireo is comprised of up to fifteen different materials, from birch bark to spider web
Every bird species builds a distinctive nest, but nests built in trees are usually framed with sticks or strips of bark, with pine needles or straw woven into the sides, and animal fur and other soft, insulating materials lining the insides. They are meant to stay warm in the middle. The same is true of bird nest compost, where hot-rotting stuff is placed in the centre, which is insulated by coarser materials that take longer to decompose.
![Cross-section of a bird nest compost pile]()
Cross-section of a bird nest compost pile
How to Build a Bird Nest Compost Pile
To build a bird nest compost pile, you can start from scratch or fine-tune a heap you already have going. Use a hoe or digging fork to hollow out a centre 12 to 14 inches (30 to 35 cm) wide and almost as deep as the heap. Fill the hole with nitrogen-rich “hot” materials such as manure, poultry or alfalfa pellets, grain products, half-done food waste compost or grass clippings. Add water after each addition, and dampen the adjacent garden waste as it accumulates, too.
From time to time as weather permits, aerate the centre by chopping through it with a metal stake or stout stick before adding more fast-rotting materials. When watering, use lukewarm rather than cold water to help raise the temperature in the heart of the heap.
The core will shrink down faster than the rest of the heap, enabling it to capture rain, while creating room for more compostable materials. Expect the centre of your bird nest compost to widen naturally as the decomposition process moves sideways into the moist garden waste.
![Covered bird nest compost pile]()
A heavy pail is handy for covering the centre of a bird nest compost as the rest of the heap gains size
Mallee-fowl often cover their incubating nests with sand to insulate them from cold or heat, and a simple cover can benefit a bird nest compost, too. Once winter gets serious, cover your heap with a thrift store blanket in a dark colour that will absorb heat on sunny winter days.
When temperatures rise in spring, stage a major chopping session to mix all the materials together. Dampen well, and you are on your way to a nice batch of finished bird nest compost.
