The life of sedge warblers

The life of sedge warblers

Sedge warbler (Acrocephalus schoenobaenus) adult singing in reedbed. Cambridgeshire. - Chris Gomersall/2020VISION

Conservation Officer Chris Hill shares his knowledge on warblers that can be spotted at Cossington Meadows Nature Reserve and includes his knowledge on the life of sedge warblers.

Cossington Meadows nature reserve has several warbler species. Chiffchaffs can be seen and heard across the reserve and willow warblers like to inhabit Brook Wood and Mill Wood. 

There is just one problem, they are very difficult to spot! When one comes into view, by the time you have found it with your binoculars, they have moved away into the dense vegetation, out of sight from prying eyes!

Cetti's Warbler

Image of Cetti's Warbler

The cetti’s warbler emits a deafening sound that always makes me jump but again are difficult to spot and the grasshopper warbler makes that wonderfully distinctive reeling noise but the older you get the more inaudible it becomes. 

Garden Warbler

Garden warbler (Sylvia borin) adult in hedgerow. Cambridgeshire. - Chris Gomersall/2020VISION

Garden warbler and blackcap have similar songs and are often heard in similar habitats but again have that tendency to well, just disappear.  

Therefore, if you want to actually study a warbler for a few seconds, a reed warbler, you would think is your best bet.  But, like most warblers they are small and brown.  They do often show themselves flying backward and forwards along the edge of the water, but often become invisible when they tuck themselves away into the dense reeds.

So in my opinion, the easiest warbler to identify is the sedge warbler. They often have a tendency to sit atop a reed stem for those very important few seconds before they decide that you have had a good enough view.

Sedge warbler

WildNet - Jim Higham

Sedge Warblers are small, elusive, streaky warblers with a dark striped head and that distinctive pale eye stripe (supercilium). Male and females are also identical, they have a mottled stripy brown back and pinkish brown legs.

They are small birds, weighing only 10-13g, similar to the weight of AAA batteries! They are between 11-13cm in length and their wingspan can reach up to 21cm. A sedge warbler's average life span is around 2 years, however, the oldest recorded was 8 years and 8 months!  (British Trust for Ornithology 2001)!

Sedge warbler

WildNet - Amy Lewis

Sedge warblers can be seen from April to October in the British Isles and can be spotted in a variety of wetland habitats. Across Europe, there are between 3 and 5 million pairs and Britain can lay claim to an impressive quarter of a million pairs!  

Soon after arriving from their migration, the male will claim its new territory and begin to sing.  Sedge warbler songs are individual and are often likened to reed warblers but with scratchier overtones. Males with the greatest repertoire of melodies often have greater breeding success. 

The song is performed theatrically whilst flying a few metres up and circling, before parachuting back down.

Warbler Nest

Image of warbler nest

The cup-shaped nest is built by the female low down in the reeds and is made up of a mixture of grass stems, spider webs, animal hair, and flower heads. A female sedge warbler can lay up to 5 eggs per season and the usual incubation period is around 14 days. The chicks will then fledge after another fortnight.

Mid to late July is a great time to get out and look for juvenile birds as many would have recently fledged. They are often spotted flying weakly over vegetation and then clumsily flopping down onto a suitable perch. 

Interestingly, female sedge warblers are usually monogamous, the males are less so.  However, the males are usually faithful to their territories, returning year after year.

Sedge in reed

Sedge warbler (Acrocephalus schoenobaenus) adult singing in reedbed. Cambridgeshire. - Chris Gomersall/2020VISION

Similar to most warblers, they are primarily insectivores. Their diet consists of a variety of bugs and insects, including dragonflies, spiders, and beetles. 

When fattening up for migration, sedge warblers will consume berries, but they are known to prefer aphids. They will need to double their weight before migration, so will travel great distances to find food and can be spotted away from their usual haunts.

Migration begins in late August/September which sees them head all the way to sub-Saharan Africa. Their route will take them through South Western Iberia or Italy.  

With good fat reserves, a bird could fly non-stop for approximately 2 ½ thousand miles, lasting 75–95 hours, which is incredible considering this bird is only 13cm long. They will return to Europe in March and arrive back in Britain in April. 


Sedge warbler (Acrocephalus schoenobaenus) perched, singing at dawn, Wales, UK - Mark Hamblin/2020VISION

Sedge warbler numbers are not currently threatened.  However, climate change and the expansion of the Sahara may be a threat with the drying of wetlands, reducing food availability and adult survival.  If the distance between feeding areas increases, then birds will suffer due to flying longer distances between rests.