1.1 All shallow estuaries attract large flocks of feeding and roosting water birds. Inland waters are frequently used as gull roosts and as refuges by wildfowl and wading birds. Some areas of pasture are utilised by large flocks of feeding gulls and waders which fly to and from roosts at wetlands. In addition, large numbers of sea birds gather to breed on exposed headlands, cliffs and offshore islands. Some may visit their breeding sites throughout the year and soar high above them at times.

1.2 Many species are hazardous to aircraft. Attached maps show the main areas where flocks occur, particularly flocks of gulls, the birds responsible for most Irish bird strikes. The darker areas indicate particularly dense concentrations. Each marked concentration should be regarded as potentially hazardous out to 20-30miles from its periphery to allow for dawn and dusk roosting movements. The number of sites where large concentrations of birds are known to occur is very great but some sites will be occupied for only short periods depending on the season and weather. Starlings roosts for instance are numerous but they often change position and hence are not shown on the maps: they are dangerous at dawn and dusk and highly dangerous if they erupt at night as they sometimes do when the birds migrate.

1.3 It should be noted that the change in bird concentration areas shown on the two maps, as from one period to the other, is gradual and the greatest movements of birds are witnessed during the changeover periods, e.g. February and March.

1.4 Migration of birds in Ireland in the spring and autumn is concentrated mainly on the coast. In spring small song-birds, mainly night-flying, arrive on the South and East coasts and then spread through the country; passage migrants tend to continue northwards using the East coast as a leading line; at the same time large numbers of sea birds return from the open seas to the cliffs and offshore islands to breed. In autumn, song-birds from Iceland/Greenland, Scotland, Scandinavia etc. arrive in large numbers along the North and North-West coasts and concentrations are again found on the South-East coasts as birds depart from the country. Numbers are far greater in autumn than in spring. The largest concentrations of waders are found mainly in the larger estuaries all around the coast in spring and autumn, though some species (plovers, curlews etc.) are found in considerable and concentrations in many inland sites. Ducks, geese and swans are found in numbers in all major estuaries and many inland wetlands. The main arrivals in Autumn are on the North and North-West coasts and on the East coast. Swans and geese are found migrating at some height (up to 2,500ft) on these coasts in OCT/NOV and again from the end of FEB to the end of APR. Very large scale movements of ducks and waders especially, can be encountered (usually moving East-West) at any time from NOV to MAR.

1.5 Height data for migratory movements is inadequate but even under favourable conditions most migrants fly below 5,000ft AGL.

1.6 Meteorological conditions play a dominant role in determining the behaviour of birds especially migratory patterns and routes but also affecting concentrations in feeding areas and routes the occurrence of soaring behaviour. Disorientation in fog also occurs. The greatest numbers of birds migrate in clear weather and calm conditions or with a following wind. The biggest movements are initiated by the onset of cold weather in winter. Diurnal migrants depart at dawn, peak numbers on the move occurring during the first few hours of daylight and falling off during the day.Nocturnal migrants depart at dusk, peak numbers occurring during hours of darkness, but many may still be flying at dawn and some species of birds will carry on all day too. Birds which make long sea crossings may not arrive until after the normal peak migration hours.