The implications of this disadvantage are assessed by means of a computer model of metapopulation dynamics, in which individual colonies are established through different rates of immigration and suffer different rates of local extinction. Males and females are at a selective disadvantage relative to hermaphrodites (cosexuals) in species with a colonizing habit, as only cosexuals are able to establish new colonies on their own. The types of habitats present in the landscape and how they are managed, along with the structure of the landscape, determine species diversity of birds and butterflies in lowland Irish landscapes. Large areas of arable land and coniferous forest had negative effects on butterfly diversity. Butterfly diversity in the landscape was influenced by heterogeneity of habitat patches with grassland and forest patches having positive effects. The presence of areas of grassland and mature mixed forest in the landscape were more important for birds in winter. In the breeding season, area of forest had a negative influence on bird diversity while large unfragmented areas of grassland had positive effects. Landscape structure was also shown to be important for bird and butterfly diversity in lowland Ireland. The majority of field interior species including skylark, meadow pipit, pheasant and snipe showed a preference for non-rotational set-aside over rotational set-aside and the other management types. The type of management of set-aside was important and determined which species were likely to be found using the set-aside field. In lowland farmland in Ireland, bird species diversity in the breeding season was greater in set-aside compared to neighbouring farmland. The numbers of butterflies and species recorded were higher from transects placed along hedgerows compared to those in the middle of fields in the same farmland site. Individual species showed preference for different aspects of local habitat and vegetation structure including the presence of larval foodplants. However, this may have been due to the low numbers recorded. Farmland habitats contributed more unique species to the total bird diversity, which probably reflects the lack of woodland specialists in Ireland.įarmland and woodland habitats did not differ significantly in terms of butterfly species diversity and abundance.

The habitats differed in the bird species assemblages they contained both in summer and winter. However, in winter this was not the case. In the breeding season, bird species richness and abundances were significantly different between the habitats studied: broadleaf forest, coniferous forest, pasture, set-aside and tillage. Similar studies have been conducted in Britain and other European countries but it was believed that the situation might have been different in Ireland due to the island status, the physical environment and history of landuse of the country, which have resulted in impoverished bird and butterfly faunas. This study examined bird and butterfly diversity in agricultural land and woodland in Irish lowland landscapes in Co.

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