Increase in Gadwall numbers welcome news
The departure of Swallows and other summer migrants and the arrival of autumn heralds the imminent influx of wintering waterbirds.
Wintering waterbirds are the species of wild birds that come here annually to spend the colder months of the year with us. Our milder oceanic climate attracts them when colder parts of mainland Europe are locked in the chilly embrace of an enveloping blanket of ice and/or snow.
Some 800,000 individual wintering waterbirds arrive here each year comprising about 70 species. A recent report on the status and distribution of these winter visitors to our shores found that there has been a reduction in numbers in Ireland of about 15% during the period 2012-2016 relative to the previous survey period 2007-2011.
At over 80%, Scaup showed the greatest decline. Goldeneye and Pochard were down over 50%. Mallard, Pintail, Red-breasted Merganser, Shoveler and Tufted Duck were all down by over 25%.
But it wasn’t all bad news. Gadwall and Little Egret both showed dramatic increases while Grey Heron and Little Grebe numbers were well up.
The increase in Gadwall must be welcomed as good news but the welcome has to be dampened by the knowledge that the species is the duck most associated with polluted waters. Furthermore, the increase of 54.9% was calculated over a 22-year period and masks a decline of 39.3% during the most recent survey period (2012-2016).
Smaller and slimmer than a female Mallard, the Gadwall is an elegant greyish-brown dabbling duck easily recognised, especially in mature males, by its distinctive small white square patch, like a sugar cube, on its side when swimming or on the rear of its wings when flying.
The Gadwall’s diet comprises mainly seeds and aquatic vegetation with some insects.
Male Gadwall, especially in breeding plumage, are distinctive in that they exhibit markings called vermiculation as featured in the image above. A vermiculation is a mark in the form of a fine wavy line resembling the track made by a crawling worm. Vermiculation is a popular form of decoration used in architecture where wavy lines are cut into the surface of stone to form a repeating pattern.
Gadwall are not a common duck in Ireland. About 900 birds winter here each year, some 400 in Northern Ireland and about 500 scattered throughout the Republic. Smaller numbers of the wintering birds stay to breed in summer nesting in localised areas by shallow freshwater lakes and brackish lagoons with abundant vegetation.