Dunnock system can be shifted from one that favours female success (polyandry), to one that promotes male success (monogamy, polygynandry, or polygyny). The dunnock builds a neat nest (predominantly from twigs and moss and lined with soft materials such as wool or feathers), low in a bush or conifer, where adults typically lay three to five unspotted blue eggs. Broods, depending on the population, can be raised by a lone female, multiple females with the part-time help of a male, multiple females with full-time help by a male, or by multiple females and multiple males. In pairs, the male and the
Bird colony (Enantiornithes), in sediments from the Late Cretaceous (Maastrichtian) of Romania. Approximately 13% of all bird species nest colonially. Nesting colonies are very common among seabirds on cliffs and islands. Nearly 95% of seabirds are colonial, leading to the usage, seabird colony, sometimes called a rookery. Many species of terns nest in colonies on the ground. Herons, egrets, storks, and other large waterfowl also nest communally in what are called heronries. Colony nesting may be an evolutionary response to a shortage of safe nesting sites and abundance or unpredictable food sources which are far away from the nest sites. Colony-nesting birds