Dartford Warbler

In March, the males already start their first display flights. In the early days of April, except in case of rain, it is common to hear their uninterrupted singing which is short and low intensity, but can still be heard from far away. As each couple occupies a very small territory, the males perform modest exhibitions, flying with outstretched wings and tail, and landing while swelling their facial and head feathers, which seem bigger for such a small bird. In the south of Europe, the start of breeding is closely linked to temperature and rainfall. The nests that the males build are simply some dry tufts of grass accumulated together so that it can be sometimes difficult to know if it is truly a nest or just some random vegetation.

Most of them are found in low heather (Calluna vulgaris) or in thorny bushes, some of them, rarely, in brambles. The height varies: very low in heather, around 25 cm, between 40 cm and 1,30 m in thorny bushes, and the average height is between 50 and 80 cm in brambles.
The female does most of the work, arranging and reorganising the dry grass and moss on the structure previously setup by the male. Inside it is filled with dry heather stalks, rootlets, fine grass, wool and some feathers. She also adds hair, horsehair and spider webs which cover and compress the edges of the nest. From 10th April, the nests are ready in many places, but the eggs don't generally begin to be laid until the second fortnight of the month.Normally composed of 3-4 eggs, occasionally 5, six-egg clutches are exceptional. Their color is a pale greenish-gray or beige with small olive-brown, ash-gray or reddish-brown spots, usually spread out across the entire surface, but sometimes concentrated at one end of the egg. Many Dartford Warblers do not start egg-laying until the first week of May. Incubation is almost entirely done by the female and is rarely relieved by the male. The chicks, hatching after 12 or 13 days, are born without feathers and with a very dark skin. The inside of their mouths are pale yellow with two black spots at the base of the tongue. Both parents take care of the feeding of the young, gorging them on insects and especially small caterpillars. The chicks leave the nest after 12 or 13 days, but may anticipate their departure if disturbed or if subjected to too much heat. Dartford Warblers carry out two broods per season. The eventuality of a third brood is possible if the conditions are favorable.