The Willow Warbler is almost indistinguishable from the Chiffchaff.
This tiny warbler has greenish-brown upper parts, buff underparts and with a pale stripe above the eye. The Willow Warbler is more yellow, has a longer supercilium and often (but not always) has paler legs than the Chiffchaff. The bill is pale brown and the legs are pale to dark brown.
Closer inspection and a keen eye reveal that Willow Warblers also have longer wings and no eye-ring.
| Legs | Wing | Eyebrow | Tail | |
|---|---|---|---|---|
| Chiffchaff | Dark | Short | Short/Dull | Wags |
| Willow Warbler | Pale | Long | Long/Distinct | Flicks |
In the autumn juveniles with fresh plumage can be very yellow looking.
| Scientific Name | Phylloscopus trochilus |
| Length | 10-11.5 cm (4") |
| Wing Span | 16-22 cm (6-9") |
| Weight | 6-10 g (¼-½ oz) |
| Breeding Pairs | 2300000 |
| Present | Summer |
| Status | Amber |
The best way of telling Willow Warbler and Chiffchaff apart is by their song. The Willow Warbler's song is a melodic rippling phrase that rises quickly before slowly dying away.
Their calls are almost identical, but in the autumn they rarely sing so the call is often the easiest way of finding the warbler even if you cannot tell them apart.
Willow Warblers feed on insects, and are unlikely to visit bird feeders. They are often seen fluttering at the ends of leaves and branches; in fact, they are searching the undersides of the leaves for aphids because this is where the aphids feed on the tree's sap.
Gardens with lots of shrubs that encourage insects may entice Willow Warblers.
The domed nest, made from grass, rotten wood, moss and roots, is on the ground but among shrubs or grass. The nest has a side entrance and is lined with fine roots and feathers.
The smooth, glossy white eggs are speckled with reddish-brown, and approximately 15 mm by 13 mm. The female incubates the eggs by herself. After the young hatch, they are fed by both parents.
| Breeding Starts | Clutches | Eggs | Incubation (days) | Fledge (days) |
|---|---|---|---|---|
| April-May | 1-2 | 3-9 | 13 | 13-16 |
Willow Warblers are summer visitors, appearing in the UK from about late March or early April after having spent the winter in Africa, south of the Sahara.
Their migration is further than that of the Chiffchaff and this is why they have slightly longer wings.
The Willow Warbler has been placed on the Amber List of species of conservation concern owing to recent decline in their numbers. The most likely cause of this decline is deterioration in its wintering grounds (Africa), but also changes in the management of woodland fringes in Britain.
