Listen out for the bittern boom

‘A bhunnán bhuí, is é mo léan do luí, is do chnámha sínte tar éis do ghrinn.’
Listen out for the bittern boom

Cathal Buí Mac Giolla Ghunna’s ‘yellow bittern’ fell foul of climate change. The Little Ice Age began in Europe in the 16th Century and lasted until 1850; the winters of Cathal’s time (1680 to 1756) were severe. Marsh birds, their reed-bed haunts frozen solid, starved to death in the depths of winter and the harvesting of reeds, to thatch the roofs of a burgeoning pre-Famine population, reduced the great beds in which bitterns nested. Cathal Buí’s lament was prophetic; the bunnán’s days were numbered. It bred here for the last time in 1840.

Bitterns fared no better in Britain; they disappeared there also. Then, in 1911, a pair nested in Norfolk. Numbers increased over the next few decades but declined again. By the 1970s, however, they had bred in 11 English counties. Reed-beds were protected and wetland habitats managed. A paper, published in British Birds, claimed that the number of ‘booming’ males rose from 11 in 1997 to 104 in 2011. The bittern is prospering on the other side of the Irish Sea. Could it do so here?

The numbers visiting Ireland have increased in recent winters. ‘The occurrence of 12 since 2009 clearly suggests an upturn in fortunes for this species’ claimed the Irish Rare Bird Report for 2013. Our reed-beds don’t compare with those of East Anglia, but some of these visitors might be tempted to stay on for the summer. It’s a ‘long shot’, perhaps, but they might even breed. ‘Oh to be in (Ireland) now that April’s here’! It might be worth keeping an eye, or rather an ear, out for bitterns? They start nesting around now.

The bunnán belongs to the heron family but unlike the corréisc, wrongly called the ‘crane’ in Ireland, it doesn’t nest colonially in trees. This skulking solitary stalker has yellowish plumage with long dark-brown streaks. The eyes are directed downwards, under the bill, to spot the fish frogs and creepy crawlies it hunts. When danger threatens, the bill is raised vertically, with the eyes focused horizontally, in the famous ‘bittern posture’. Beautifully camouflaged, the bird sways back and forth with the reeds as they bend in the wind.

Bitterns may be difficult to spot among dense vegetation, but their presence is soon detected. ‘He shall not hear the bittern cry, in the wild sky where he is lain’ wrote Francis Ledwidge. This line has misled generations of Irish schoolchildren; the bittern’s ‘boom’ could not, by any stretch of the imagination, be described as a ‘cry’. To be fair to Ledwidge, he was not the only poet to be misinformed about bunnáns. Chaucer’s Wife of Bath Tale refers to the bittern sticking its bill into the mud to produce the strange sound. ‘The bittern knows his time with bill engulphed, to shake the surrounding marsh’ wrote James Thomson in his Four Seasons poem, Spring.

The low-pitched ‘fog-horn’ burst, one of the most evocative sounds in nature, is produced by swallowing and belching out air. Audible up to 5km away in calm weather, Pliny likened it to the distant roar of a bull. Indeed, bull-rushes are named for the booming of bitterns hiding among them. The ‘bull of the bog’s’ strange ‘song’ attracts females and warns challengers off his territory. Occasionally, a female answers with a weaker version of the call. He can have up to five ‘wives’ on nests in his demesne. You may catch a glimpse of the elusive bird, as he flies low over the reeds on visits to them. Nests are built, and chicks raised, by the females without any help from him.

A reed bed in summer rejoices to the jerky raucous recitals of sedge warblers and the wild screams of water-rails but, without the bittern and his booming, it’s ‘Hamlet without the Prince’.

  • Brown Gilbert & Wooton, 2012. Bitterns and bittern conservation in the UK. British Birds 104. 2012.

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