This site occupies the inner part of Donegal Bay, in the NW of Ireland. It contains the estuary of the River Eske and several other important rivers, especially for salmonid species. The area is underlain by limestone and carboniferous shales, although sand and other recent deposits hide much of the geology.

The site is a SAC selected for the following habitats and/or species from Annexes I/II of Directive 92/43/EEC (priority types are indicated with an asterisk, the area in hectares is shown in parentheses):

1140 Tidal Mudflats and Sandflats (1068.53 ha)

*2130 Fixed Dunes (Grey Dunes) (27.01 ha)

2170 Dunes with Creeping Willow (7.0 ha)

2190 Humid Dune Slacks (0.12 ha)

1365 Common (Harbour) Seal (Phoca vitulina)

Most of the site consists of intertidal habitats, particularly mudflats and sand flats, inlets and bays, estuaries, estuarine channels, and sandy beaches. These areas are generally unvegetated, but are obviously rich in nutrients, as there are extensive shellfish beds in parts of the bay. The following macroinvertebrate species are common throughout much of the bay: Arenicola marina, Hediste diversicolor, Scrobicularia plana, and Macoma balthica.

Along some parts of the coast, salt marsh has developed. Dominant plants include Armeria maritima, Festuca rubra, and Cochlearia officinalis. Triglochin maritima, Juncus acutus, and J. gerardi are also common, while brown algae (Fucus spp.) are abundant in the lower part of the coastal profile.

On the stable parts of some of the pebble and rock beaches, Cochlearia officinalis is also found, along with Potentilla anserina and Glaux maritima.

Sand dunes, including fixed dunes, are present on the site, especially at Murvagh. Intact sections contain Honkenya peploides and Ammophila arenaria in the young dunes, with abundant Ammophila arenaria in the fixed dunes. These stable areas are often species-rich, with abundant Luzula campestris, a well-developed moss community including Thuidium tamariscinum and Rhytidiadelphus squarrosus, and grasses such as Lotus corniculatus, Thymus praecox, Viola canina, and Galium verum. Typical 2170 species are found on Mullanasole and include Salix repens, Carex arenaria, Festuca rubra, Galium verum, Pilosella officinarum. Fixed dunes 2130* support Arrhenatherum elatius, Prunella vulgaris, wild thyme, Agrostis stolonifera, Ammophila arenaria, and the mosses Hypnum cupressiforme, Rhytidiadelphus triquetrus, Rhytidiadelphus squuroarzium, R. schuroarrosium, and R. plebeberi. Orchids such as Listera ovata, Epipactis helliborine, E. palsutris have been recorded in the dunes. Murvagh Recorded Plant Species listed on the Irish Red List Pyrola rotundifolia ssp. maritima) (endangered) and Monotropa hypopitys (vulnerable). Murvagh is an important site for butterflies, and records include Cupido minimus, Erynnis tages, Argynnis paphia, and Fritillary aglaja, among others.

Most of the dune habitat in the ZEC (c.19ha) is confined to the southwest of the SAC, in an area whose main use is as a golf course and forest plantations, presenting in the western limit of these a tongue of land occupied for habitat 2130*. The forest plantation area was almost completely excluded from the SAC during its designation due to the null natural value it supports, although 10.7 ha of repopulated fixed dunes are within the SAC, parts of which have very high potential. high to be restored to habitat 2130*. In addition to 2130*, there are also habitats 2190 and 2170 on the border between forest plantations and open dunes. The aforementioned strip of land was first planted with conifers in the mid-1950s by the then state forestry agency, the Forest and Wildlife Service, and was eventually transferred to COILLTE, the state forestry company. The plantation is mainly made up of Pinus nigra, Pinus radiata, Picea sitchensis, Pinus contorta, Chamaecyparis lawsoniana and Fagus sylvatica. Forestry management is approached as a biodiversity area primarily using the objective of continuous coverage. Several areas of woodland are mature and show signs of senescence, with occasional wind blows, while others are already extra-mature and open, with some native flora still present. Naturally regenerating conifers occasionally occur throughout the sand dunes.

Both Melanitta nigra and Branta bernicla hrota are found in Donegal Bay from Bundoran north to Murvagh. The bay provides one of the most important sites in the country for Melanitta nigra, with a maximum number of approximately 1,500 individuals in 1984/85 - 1986/87. This species uses large wintering areas, which makes accurate bird counting difficult, but in recent years peaks of 662 individuals (1995/96) and 1,073 individuals have been recorded in the area (1997/98).

Other notable wintering species at the site include Charadrius hiaticula 175, Haematopus ostralegus 119, and Calidris alpina 221 (data based on 18 counts from 1984/85 to 1986/87). Small numbers (up to 50) of Anser albifrons flavirostris foraged on Inishpat Island in the 1980s from nearby flocks on the Pettigo Plateau, but have rarely done so in recent years.

The Site supports a population of Phoca vitulina, with a maximum count of 148 in the 2003 All-Ireland Census. This species is listed in Annex II of Directive 92/43/EEC.