Tystie treat as auks try the inner city

Richard Collins finds an unlikely seabird on the Liffey.

THE lower reaches of the Liffey, with their infamous whiff, would not seem an attractive place for wildlife. However, while walking along the quayside past Gandon’s Custom House last year, I noticed some birds on the murky water. On closer inspection, they proved to be what are known as ‘tysties’, unlikely visitors to the heart of a city.

Something must have led these seabirds astray, I thought, that they ended up in such an unsuitable location; they would soon see the error of their ways and be off to more appropriate waters. But I was wrong. Each time I visit the stretch of the Liffey just downstream of Butt Bridge, tysties are present. There were a dozen of them there last Wednesday.

Tystie is the Scottish name for the black guillemot; it comes from old Norse and is thought to be an imitation of the bird’s call. The standard name, black guillemot, is not really appropriate; guillemots and black guillemots are members of the auk family, but they belong to different genera and they are not that closely related. The don’t even look alike.

The dumpy little tystie is far less numerous in Ireland than any of the other auks. According to the Atlas of Breeding Birds in Britain and Ireland, there are only about 3,000 black guillemots here, compared to 153,000 guillemots and 41,000 puffins. With so few of them around our shores, it is odd that black guillemots should frequent the centre of Dublin.

In summer, tysties are black all over, apart from their bright red legs and a gleaming white patch on each wing. Guillemots razorbills and puffins are dark above and white below, a subtle camouflage scheme. When these birds sit on the water, the dark parts are above the surface, making it difficult for predators, such as sea eagles, to see them against the dark sea surface. Their bellies under the water, however, are white and the fish on which they prey find it harder to spot them against the brightness above them.

So why don’t tysties use this two-tone colour scheme? The explanation is that the black guillemot is a bottom-feeder of fairly shallow waters close to rocky shores. It spends much of its time under dark cliffs or in caves. Had it a white belly like the other auks, it would be more easily noticed by the fish. Being black all over helps it to avoid being seen in these dark places.

But, in winter, black guillemots become almost white. This too is an adaptation for security and fishing. White plumage camouflages the bird against a background of snow and ice, providing protection from enemies during the Arctic winter. Black guillemots hunt closer to pack-ice than other auks; being white, they are less visible to the fish. This is essentially a Nordic species, the Irish population being the most southerly one on this side of the Atlantic.

Winter or summer, colour schemes are probably irrelevant in the murky depths of Anna Livia. The river’s silt-laden water, mixed with the salty incoming tide, is probably similar to that of the enclosed Baltic Sea, which is almost fresh and where black guillemots thrive.

But what can the birds be catching here? Tysties are powerful underwater swimmers. They can stay submerged for up to a minute and travel 75 metres along the bottom during a single dive. Opportunistic feeders, they will take fish, crabs and molluscs. A team from the zoology department at Trinity College carried out a survey of the fish at Butt Bridge in 1985. They caught a huge number of eels. There were also some flounder and mullet. Small eels and flounder are eaten by tysties, although mullet are too large for them to tackle.

Black guillemots don’t breed in docklands and the birds in the centre of Dublin, at this time of year, are probably young; tysties seldom breed until they are four years old. The nearest nests are 12km away in Howth. Like the human residents of the inner city, black guillemots don’t like to commute. The other auk species fly considerable distances to catch fish for their young, but black guillemots stay close to home.

The approach has its limitations. Local fish supplies soon come under pressure and can’t sustain too many birds, so black guillemot pairs either nest alone or in small groups. Tysties are among the least sociable of seabirds. Huge seabird cities, such as the one on Lambay island with its 60,000 guillemot nests, are out.

One of the advantages of fishing close to the nest location is that tysties can afford to have two eggs. Some pairs can manage only one, but occasionally a pair has three. All the other auks lay only one.

Food obtained locally can be delivered to the babies quickly and they can be fed more frequently. Seabirds which make long commuting journeys can’t keep more than one baby fed at a time. Their very low reproductive rate is a major problem for seabirds. Being able to have two babies is a bonus.

The nest is a modest affair, a depression among boulders or a hole in a cliff. No material is added but the pair become attached to the site, returning to it year after year.

‘Be it ever so humble, there’s no place like home.’