The ecology of Twite Carduelis flavirostris in Ireland

Abstract

The Twite Carduelis flavirostris is one of only three passerine species to appear on the red list of Birds of Conservation Concern in Ireland. It is also listed in The Irish Red Data Book of endangered species. Despite its unfavourable conservation status, no previous study has ever focused on this bird in Ireland. Data on Irish Twite has been sparse and largely anecdotal because it mainly relied upon the observations of birdwatchers. It also lacked ecological precision or information on demographics. Population surveys in this study found north county Mayo and west county Donegal to be the two breeding strongholds, accounting for a combined total of 40 pairs. Based on this data, and various verified records, it is estimated that the national population is between 54 and 110 breeding pairs with a minimum of 650-1,100 birds wintering here. Applying these figures to the IUCN Red Data Book criteria, Twite are 'Endangered' and can be considered at 'high risk of extinction in the wild' in Ireland. Nesting habitat for Twite in Ireland comprises good quality long Heather Calluna vulgaris, and occasionally Bracken Pteridium aquilitium. For foraging, Twite selected dry-humid acid grassland, saltmarsh and artificial surfaces such as small weedy roads and roadside verges. Twite targeted the seed of more than 20 plant species depending on their availability, particularly; Taraxacum agg., Rumex acetosa, Stellaria media, and Plantago maritima. Freshwater streams provide an important habitat for bathing, drinking, and picking up grit. It was found that foraging habitats were always within 2.5 km of the nest sites. Twite remain in their breeding areas from late April to September and generally over-winter within 30 km of their breeding areas. Winter flocks primarily forage for seed at cattle ringfeeders, saltmarshes, and sea drift lines. Overgrazing and changes in land use represent the main threats to Twite. Measures to conserve Twite as a breeding species in Ireland must include the maintenance and creation a heterogeneous mix of moorland, particularly long Heather, and avoid agricultural improvement (e.g. reseeds) in foraging areas.