Nest building date begun and finished 195665

1956 1957 1958 1959 I960 1961 1962 1963 1964 1965 Nest begun 19.5 25.5 23.5 14.5 22 5 22.5 17.5 18.5 23.5

Nesi finished 27.5 2.6 315 22.5 30.5 30.5 25.5 26.5 30.5

It therefore takes an average of nine days to build the nest.

In 1968 a small bat was found in an 'All-year' nest box for pied flycatchers. It left the box at 9pm one evening, and at 3am the next morning a flycatcher frantically started to build a nest, which it had completed by 10 pm the following evening. The batdid not return for30 hours. The female flycatcher had been trying to build her nest for a long time before this, but presumably had been put off by the bat's presence or its copious cxcremcnt. These droppings have a strong smell of musk, but I do not think this was particularly significant bccausc of the bird's poor sense of smell. The bat, in the meantime, stayed in the very uppermost part of the box. The flycatcher finished her nest and even laid one egg. but she subsequently abandoned everything. Good neighbourliness was clearly not in e\ idence here. The flycatcher pair moved to another nest box in the vicinity and bred normally.

In many eases these unlikely neighbours have lived together in harmony, in one instance the pied flycatchers producing eight young in the bottom of the box while four bats and their young occupied the top.

In my study area pied flycatchers build two types of nests. Some build their nest mainly from flakes of pine bark and the previous year's birch leaves, while some combine the latter with dead grasses. 1 his suggests an inherited, unchangeable pattern of nest building. Flycatchers which begin by building normal nests continue to do so all their lives, and vice-versa.

The 'normal' nest consists primarily of heavy flakes broken by the flycatcher from trunks of pine trees, combined with a large amount of the previous year's leaves, a tiny quantity of birch bark, and some dead grass. The nest also contains flakes of juniper bark, dried fern, old pine needles, root fibres, lichen, small feathers, and down. The grass, down, and small feathers form the inner lining of the nest cup, which is warm and smooth for the eggs. The grass nest consists almost entirely of the previous year's grass, but also a significant amount of dead birch leaves and smaller amounts of juniper bark (twice as much as in the 'normal' nest), last year's oak leaves, birch bark, flakes of pine bark (only a quarter the amount found in the 'normal" nest), and lichen. Small feathers and down may form the inner lining or may be absent.

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