© Copyright: Images: Jari Peltomäki, Simo Mikkonen, M. & W. von Wright: Svenska fåglar (Kansalliskirjasto, The National Library of Finland). Recording: Jan-Erik Bruun. All rights reserved.
- Family: Leaf warblers – Phylloscopidae
- Appearance: Very similar to Willow Warbler, but expert observers can distinguish them by the less distinct markings on their heads, their darker legs and their more rounded wingtips.
- Size: Length 10–12 cm, weight 6–9 g.
- Nest: Usually on the ground, sometimes in a low spruce sapling. Ball-shaped, made of dry grass and moss, lined with grasses and dark feathers.
- Breeding: Lays 4–8 eggs in May. Female incubates for 13–16 days. Fledglings remain in nest for 13–15 days.
- Distribution: Breeds in coniferous and mixed forest from Southern Finland as far north as Northern Ostrobothnia. Finnish breeding population estimated at 100,000–150,000 pairs. Individuals of Siberian race (P. c. tristis) occasionally observed in Finland in autumn.
- Migration: Nocturnal. Leaves Finland September–October, returning April–May. Winters in tropical Africa and around the Mediterranean.
- Diet: Invertebrates.
- Calls: A soft “huit”. Song a distinctive and repetitive “chiff-chaff”, which gives the species its name.
Chiffchaffs are slightly smaller than their more common relative the Willow Warbler, and their plumage is also less glossy. In their summer plumage their grey-brown upper parts only have a slight greenish tinge, and their pale underparts are only yellowish around their flanks. In autumn plumage their upper parts are greener and their under parts more yellowish, but they still look duller than Willow Warblers and often have beige colouring on their flanks. They are most easily distinguished from Willow Warblers by their song, their darker legs, their slightly thinner and darker beaks, and their more rounded wingtips. Chiffchaffs have shiny dark brown legs, dark brown beaks with yellowish brown lower mandibles, and dark brown irises.