about twice that for solitary birds. In some areas, wintering birds have developed the habit of coming to feeding stations and bird tables for fatty food, sometimes with goldcrests or warblers such as the common chiffchaff and blackcap. The kinglet's digestive system is adapted to an entirely insectivorous diet, whereas Sylvia warblers include fruit in their autumn diet. A Spanish study compared that genus with the insectivorous firecrest and Phylloscopus warblers. The results showed that, relative to body weight, the insect-eaters had shorter intestines, but longer gut passage times than the Sylvia species. The insect-eaters are also generally slightly smaller than the omnivores. Voice The contact call is three or four thin high notes, similar to that of goldcrest, but slightly lower in pitch, zit-zit-zit rather than see-see-see. The song is a succession of call notes in a longer and slightly more varied sequence. Typically there are 11–14 notes per song, becoming louder and faster, with the final three notes slightly different from the preceding ones: zit-zit-zit-zit-zit-zit-zit-zit-zit-zit-zirt.zirt.zirt. The song usually lasts 0.5–2.5 seconds, shorter than the 3.5–4.0 seconds for the goldcrest, and may be repeated up to eight times a minute. In May and June, singing is most frequent after dawn, but continues less often throughout the day. Later in the breeding season, song becomes largely confined to the morning. The song of the Mediterranean subspecies of common firecrest, R. i. balearicus, is very similar to that of the nominate form, but one factor in separating the Madeiran firecrest from common firecrest is that the island bird's song is divided into three phrases, two of them consisting of modified display and anger calls. Its display calls also use a larger frequency range and more harmonics than those of the continental subspecies. Male goldcrests and Madeiran firecrests sometimes show a territorial response to recordings of the songs or calls of the common firecrest, but the reverse is apparently not true, because the songs of the common firecrest are simpler in construction than those of its relatives. Predators and parasites Throughout the firecrest's range, the main predator of small woodland birds is the Eurasian sparrowhawk, which takes avian prey as up to 98% of its diet. The tawny owl relies more on mammalian catches, but about one-third of its food is forest birds. Eggs and young may be taken by grey squirrels, Eurasian jays and great spotted woodpeckers. The firecrest appears to