Sylvia undata is a patchily distributed resident across parts of south-western Europe, which constitutes >95% of its global range. Its European breeding population is very large (>1,900,000 pairs), but underwent a large decline between 1970-1990. Although the trend of the stronghold population in Spain during 1990-2000 was unknown, the species was stable or increased elsewhere in its European range. Nevertheless, its total population size has probably not recovered to the level that preceded its decline, and consequently the species is provisionally evaluated as Depleted.
This small warbler inhabits north-western Africa and south-western Europe, from the Iberian Peninsula to Italy and southernmost England. Parts of its populations are sedentary; parts make small-scale movements and a few birds reach north-western Africa. The population of the European Union, which represents nearly the entire world population, is estimated at 1.8-4.1 millions of breeding pairs. However, since the beginning of the 1970's, this species is declining in Spain. Elsewhere it fluctuates or remains stable. Intensification of agriculture and habitat destruction - Mediterranean thickets in the south, dry heath in the north - are the main threats to this species. Too frequent fires are also detrimental

Shows some preference for maritime regions and islands, but in south of range ascends to uplands, and even to c. 1500 m in Spain. In southern Europe, mainly frequents open garigue; in north-west Spain, also in low pine woods; in North Africa, confined to largely hilly coastal scrub with kermes oak. In England, breeding habitat is almost entirely lowland heath dominated either by gorse or by heaths; in some places, bramble and, to less extent, bracken or grasses may serve as substitutes.

Egg laying in Southern England from mid-April. Jersey (Channel Islands) eggs at end of March to July. Provence (southern France) and southern Spain: eggs from early April. usually 2 broods, exceptionally 3. Nest is built in dense, often evergreen bushes. Nest is a compact cup of grass leaves and stems, and bits of heather, usually with vegetable down, cobwebs, and occasionally feathers, sometimes with distinct middle layer of plant down; lining (inner layer) of finer material including rootlets and hair. Clutch varies from 3-5 and are incubated for 12-14 days.

Diet includes the following: Invertebrates: damsel flies, grasshoppers, bugs, adult and larval moths and butterflies, flies, wasps, beetles, spiders, harvestmen, millipedes and snails. Plant material: berries of bramble Rubus, spurge-laurel Daphne, myrtle Myrtus, pistachio Pistacia.
Observed carrying caterpillars from heather to gorse where they were beaten on stem. In summer, seen to pick and presumably eat small items while carrying caterpillar for young. Adults feed moths to young complete with wings. Large grasshoppers are fed whole, abdomen first.

This species has a large range, with an estimated global Extent of Occurrence of 100,000-1,000,000 km². It has a large global population, including an estimated 3,700,000-7,500,000 individuals in Europe (BirdLife International in prep.). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.

Partially migratory and dispersive. Many birds remain all year on breeding grounds, but autumn and winter records are frequent in non-breeding areas, probably chiefly juveniles. In Mediterranean, presence in winter on islands where none breed shows that some birds undertake sea crossings: scarce but regular visitor to Malta and Balearic Islands (and Menorca now colonized: see Distribution). Some European birds reach north-west Africa, vagrants occur far afield.

article number 1 Title
Habitat type determines the effects of disturbance on the breeding productivity of the Dartford Warbler Sylvia undata
Author(s): GISELLE MURISON, JAMES M. BULLOCK et al.
Abstract: Numerous studies have examined the causes and impacts of human disturbance on birds, but little is known about how these impacts vary among habitats. This is of applied importance both for predicting ..[more]..
Source: Ibis 149 (s1), 16-26
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article number 2 Title
Territory characteristics and coexistence with heterospecifics in the Dartford warbler Sylvia undata across a habitat gradient
Author(s): Pere Pons et al
Abstract: The study of successional gradients may help to understand the relative influence of habitat structure and competition on territory characteristics. Here, we evaluate the effects of vegetation cover, ..[more]..
Source: Behav Ecol Sociobiol (2008) 62:1217-1228
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