An Irish Nature Year

27th Barn swallows are returning to Ireland. The first few individuals have been flying in from their wintering grounds in southern Africa over the last couple of weeks. These are most likely males, who arrive before the females to establish a nest site. Birds remain faithful to the same nest places from year to year, building their mud and straw cups up against the beams inside barns and sheds. Swallows can be distinguished from their cousins, the martins, by their high-low, swooping, gliding flight and their lengthy, deeply forked tails. Females’ tails are a little shorter. Males with the longest, most symmetrical tail streamers are the most sought after. Swallows often gather communally on wires, nattering constantly in lightweight, liquid voices. They will raise two or even three broods of young before returning south for the winter. Swallows feed entirely on insects, favouring larger flies such as horseflies and bluebottles. Their food supply suffers where pesticides are used, including animal worming medications. Such drugs render cowpats sterile, so that flies’ eggs don’t hatch on them.

28th Solitary bees are emerging from their nests and are feeding on dandelion and willow flowers. Unlike honeybees or bumblebees, they do not form cooperative communities. Instead, the young raise themselves, having been provided with the equivalent of a packed lunch by their mother. After mating in late spring or summer, she searches for a suitable nest site. This might be in an earthen bank, a crack in masonry, or even a manmade ‘bee hotel’, depending on her species. She collects pollen, makes it into a cake and lays a single egg on it. She repeats the process – one cake, one egg – until her eggs are finished, after which she dies. The larvae hatch, feed on the pollen and overwinter in cocoons. In spring they emerge as adults and the cycle starts again. A few species are ‘kleptoparasites’, laying eggs in the nests of other solitary bees. Most of our seventy-seven solitary bee species are smaller than a honeybee. Some are very efficient pollinators. They carry pollen on the underside of the abdomen, instead of on the legs: with each flower visit, pollen is left behind. The red mason bee (Osmia bicornis), which readily uses bee hotels, can provide 120 times the pollinating services of a honeybee.

29th Violets are in flower. We have several species, but the common dog violet (Viola riviniana) is by far the most widespread – in woodlands, banks, hedgerows and pastures. The ‘dog’ denotes that it has no scent, unlike the sweet violet. In parts of Britain, ‘horse’ and ‘pig’ replace the dog. Its pale purple flowers are borne singly and the leaves are hairless and heart-shaped. You can tell it apart from the similar early dog violet (V. reichenbachiana) because its spur (the tiny finger at the back of the flower) is pale, instead of dark. Or maybe you can’t: the two species have intermingled, especially in Leinster, and it can be hard to put a name on some plants. Violets have multiple interactions with insects. The flowers provide valuable early forage for bees, while the caterpillars of certain fritillary butterflies feed on the foliage. Violet seeds have a fatty appendage, called an elaiosome. This attracts ants, which unwittingly disperse them by transporting them to their nests. After the elaiosome is eaten, the seed is removed to a ‘rubbish’ area, where other organic matter makes the soil more fertile. The seedlings from these natural compost heaps have larger leaves than others.

30th The first basking sharks of the year are appearing off the coast of Ireland. Between now and late autumn, hundreds will be seen, mainly ranging from Waterford, along the west coast and up to the north coast of Donegal. During May and June, the cliffs of the Inishowen Peninsula, Ireland’s most northerly point, are a good place from which to spot them. One of the vernacular names is ainmhide na seolta (monster with the sails), because of the huge tail fin. It is also known as the ‘sun-fish’ because of its habit of basking near the surface on sunny days.iii Cetorhinus maximus is the largest fish in the north Atlantic, and the second largest in the world (after the whale shark). The usual length is five to seven metres, but the longest known individual was over twelve metres. It swims around with its massive mouth open, straining dozens of kilos of plankton per day into its digestive system. Seen from above, they are huge-headed, majestic creatures, swinging their rudder of a tail from side-to-side as they curve slowly through the water. Basking sharks migrate to deeper waters in the autumn, but occasionally they go farther. In 2012, a shark tagged off Donegal travelled over five thousand kilometres to tropical waters off West Africa. In 2019, another shark, also tagged off Donegal, was photographed off Cape Cod in Massachusetts.

31st Geese that have overwintered in Ireland are starting to make the journey north to their various breeding grounds. Pale-bellied brent geese from Dublin Bay have been stopping to feed at Carlingford Lough and at Killough in County Down. They will eventually end up in eastern High Arctic Canada via Iceland and Greenland. Meanwhile, the huge population of Greenland white-fronted geese (around 8,500), which winters in the Wexford Slobs, is also on the move. They usually begin to depart around now and continue to do so over the coming weeks. Like all geese, they travel in groups composed of family units, and let warm winds from the south help them on their way. They also break the journey in Iceland, a destination they can reach in eighteen hours if assisted by a following wind. Barnacle geese from Greenland, which overwinter in the west of Ireland, likewise stop in Iceland. The arduous journey can burn a huge amount of fat: up to a third of a goose’s body weight. It takes several weeks to build up their reserves again.

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