For me, much of the early summer is spent looking at nests. Regardless of how many nests I see I am still amazed by the technical ability that goes into their construction. Admittedly there are some nests that are rather basic affairs, with little more than a few twigs placed together in a manner that, more often than not, leaves the nest contents in real danger of falling to the ground beneath. Most nests, however, are more solid in their construction and these provide a secure environment for the eggs and resulting young.
Many nests are made of several distinct layers of material, typically with bulkier material in the base and around the outside, finer material within this and a lining of feathers or other soft material. Some species reinforce their nests with mud, something which song thrushes take to an extreme with their lining of mud, rotten wood and saliva, which dries to a form of ‘woodchip’, rigid in structure and thought to reduce the attractiveness of the nest to nest parasites.
Some of the most delicate nests are those made by our warblers. Blackcaps and garden warblers, for example, construct their nests from fine grasses, the nest itself placed in thick bramble or nettle cover, while reed warblers use grasses, material from reed flowers and plant down in their nests, which are tied into to the vertical reed stems that support them. On occasion the amount of white plant down in a reed warbler nest can make it appear as if the nest is constructed entirely from wool.
Nests may incorporate all sorts of other materials. Red kites, for example, are known to add clothing taken from washing lines to their bulky nests, while many birds add feathers or animal fur, scavenged from the local area. Dog and cat fur, left out in the garden after a pet has been groomed, is often well used by nesting tits. Longer hairs can sometimes be a problem, however, the bird or its chicks getting caught in the material if it forms a loop. The same can be said for discarded wire or fishing line. Birds are certainly resourceful when it comes to sourcing nest material, so it is important for us to be aware of the consequences of leaving unsuitable material in our gardens or the countryside.