Highlighting the marsh harrier

Renowned as a silent, stealthy predator, the marsh harrier has gone from near-extinction to breeding success in the UK. David Chapman is captivated…

The dark silhouette of a bird glides low across the top of the reeds. It is the size of a buzzard, holding its wings at an upward angle to create a distinctive shallow ‘V’ shape, the tips splaying to reveal individual primary feathers like fingers on a hand. Closer the bird comes until I can make out a creamy, almost golden, pattern around its head and ‘elbow’. In an instant it turns, doing a complete circle, its wings higher now, and its talons dangling in anticipation as it drops into the reeds.

This is a female marsh harrier. A silent and stealthy predator, she has spotted something of interest, maybe a small mammal or bird, and taken her opportunity.

The marsh harrier’s ability to turn full circle when hunting is reflected in its Latin name, Circus aeruginosus − ‘circus’ means ‘circle’, while ‘aeruginosus’ means ‘rusty’, a nod to the bird’s plumage. In a nutshell, marsh harriers are well-camouflaged and nimble hunters, able to rise and fall skilfully and without sound on their agile wings. Manufacturer Hawker Siddeley acknowledged this ability when, in the 1960s, it named its new fighter the ‘Hawker Harrier’. This aircraft, which became known as the Harrier Jump Jet, was able to take off and land vertically, and was incredibly versatile.

Compared to the females, male marsh harriers are slightly smaller and slimmer, with more elongated wings. Their plumage is quite different, being notable for its grey wings and black wing tips (females are predominantly dark brown with creamy-yellow accoutrements). However, the exact plumage patterns on both male and female birds develop with age and are quite variable.

At a time when many bird populations have declined it’s refreshing to see a species that is on the up. Though marsh harriers were hunted to near-extinction in the 19th century and only bred sporadically during the early 20th, their fortunes changed significantly in 1971 when the one remaining pair mated successfully in Suffolk. Since then they have gradually spread their wings thanks to the creation of more wetland which supports a whole range of species. A recent breeding bird survey estimated that there were 448 nesting pairs in the UK in 2022.

Gallery

A male marsh harrier with distinctive grey wings and black wing tips

Preening female marsh harrier

Two females fight over food

Marsh harriers are silent and stealthy hunters

Home or away?

Generally, marsh harriers are most numerous in the east of England, particularly around East Anglia, but they are spreading quickly, with birds breeding on the Somerset Levels as well as other reedbeds around England, Wales and southern Scotland.

Traditionally the marsh harrier has been regarded as a migratory species. Other breeding birds have typically headed south to Spain or Africa to over-winter, but the marsh harrier’s need to head southwards seems to have diminished, perhaps due to our milder winters. It is possible that some marsh harriers still migrate, but these are replaced by their counterparts from the colder parts of Europe, keeping the UK population fairly constant. What we do see is a tendency for them to roost in quite large groups at certain reserves through the winter, including Minsmere (Suffolk), Titchwell (Norfolk), Ham Wall (Somerset) and Martin Mere (Lancashire).

Whichever way the birds decide to spend their winter, in spring they return to their breeding reedbeds and pair up. Males try to impress females by collecting food (which might be small birds or mammals) and passing it to them in mid-air. If the hunting is very good and there are plenty of females around, a successful male marsh harrier might mate with two or even three partners, a strategy known as polygyny.

Breeding takes place in late April and May with young born about a month after egg-laying. This means that young marsh harriers fledge in mid-June and are dependent on their parents until late summer. In September some young birds will still be pestering their parents, while others will have begun dispersing to their wintering grounds.

Reed all about it!

More reedbed wildlife to look out for in September…

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Cetti’s warbler

Male bearded tit

Otters can be found in reedbeds

Migrant hawker dragonfly

Birds: Bearded tits can be seen throughout the year, particularly in eastern England and Scotland. During autumn their diet becomes seed-based and they eat grit to help digest those seeds. Cetti’s warblers can be found throughout the year − mostly in southern England − but are more often heard than seen. So too are water rails, which sound like squealing piglets. Bitterns are found in large reedbeds, especially in East Anglia and the Somerset Levels. Breeding birds such as reed and sedge warbler are due to migrate, but might still be seen in September. At this time of year, look out for large congregations of swallows and martins roosting in reedbeds as they congregate before migrating southwards.

Mammals: Look out for water voles and otters throughout the UK. The Chinese water deer is present in East Anglia and beyond.

Insects: Dragonflies are numerous in reedbed environments. Species seen in September commonly include migrant hawker, common darter, southern hawker and willow emerald damselfly.