Species notes and references to Table 1
House Sparrow Passer domesticus– Declined in urban as well as in rural areas; several causal factors mooted, including decline of food supply (insects and seeds), increased predation from an expanding cat population, increased pollution from traffic in cities, and in some areas reduced availability of nest-sites (stemming from building repairs and conversions), but further work needed. In one experiment, responded to provision of extra food on some farms where numbers previously declined, but not on others where numbers were previously stable or increasing (Hole et al. 2002). Decreased survival during the years of decline (Siriwardena et al. 1999); also increased nest success (Siriwardena et al. 2000), but no information on possible change in duration of breeding season or total seasonal productivity. Other reference: Freeman and Crick (2002).
Tree Sparrow Passer montanus– National population decline has exceeded 95%. In local conservation projects has benefited from provision of winter food (small seeds) and nestboxes, especially when sited near water, where insects are still plentiful (Field & Anderson 2004). Showed increased nest success during the years of decline, but no information on possible changes in duration of breeding season or total seasonal productivity (Siriwardena et al. 2000).
Linnet Carduelis cannabina– Reduced survival and nest success during the years of decline (Siriwardena et al. 1999, 2000), but no information available on possible change in duration of breeding season or on total seasonal productivity. In a French study, annual variations in production of fledglings influenced year-to-year population increase (Eybert et al. 1995). For importance of oilseed rape as a food source, see Moorcroft et al. (1997) and Moorcroft and Wilson (2000).
Twite Carduelis flavirostris– Has suffered in summer from loss of weeds from meadows near the moorland edge (through improved grassland management), and in winter from loss of weeds from arable land, and especially from loss of winter feeding areas of coastal saltmarsh, which have been converted to farmland (Atkinson 1998, Dierschke 2002). Additional reference: Brown et al. (1995).
Bullfinch Pyrrhula pyrrhula– Adverse habitat changes involve loss of tall thick hedgerows from farmland and loss of understorey shrubs from many deciduous woods (often through increased deer browsing). These changes also involve loss of food-plants, in addition to loss of farmland weeds. Furthermore, recovery of Sparrowhawk numbers may have confined Bullfinches to feeding close to cover (through a behavioural response), and thus reduced the total land area over which they can forage, compared with the 1960s (Newton 1967). The demographic cause of decline is uncertain (Siriwardena et al. 2001), but higher nest success was recorded during the decline (Siriwardena et al. 2000), with no information on possible change in duration of breeding season or total seasonal productivity. The latter is greatly influenced by the amount of late summer nesting (Table 1; Newton 1999, Proffitt et al. 2004).
Yellowhammer Emberiza citrinella– Breeding densities in different parts of Britain strongly correlated with the proportion of land under arable crops, with crop diversity and with hedgerow length. Decline began later than in some other seed-eaters, and most marked following loss of minority cereal crops from western areas now dominated by grass and non-cereal crops (Kyrkos 1997, Kyrkos et al. 1998). Individual nest success was higher during years of population decline (Siriwardena et al. 2000), but in one study on nine scattered farms total seasonal productivity was too low to maintain a stable population (Bradbury et al. 2000).
Cirl Bunting Emberiza cirlus– Decline attributed to lack of insect food for chicks in breeding season, and seeds in winter. Appropriate conservation measures, within the framework of an agri-environment scheme, promoted an increase in food-supplies, leading to a four-fold increase in the remnant population within 10 years (Evans & Smith 1994, Evans 1997, Wotton et al. 2000, Peach et al. 2001).
Reed Bunting Emberiza schoeniclus– Probably suffered from both land drainage and destruction of ‘rank patches’ (reducing nesting habitat) and decline in food supply (insects in summer, weed and grass seeds in winter). During the years of decline (1975–83) breeding numbers fell rapidly on arable and mixed farms, but remained relatively stable on pastoral farms (Peach et al. 1999). The decline was greater in northern Britain than in the southeast. Annual survival was lower during the years of decline (Peach et al. 1999), as was nest success (Siriwardena et al. 2000), and recent study suggests a decline in total seasonal productivity in some areas (Brickle & Peach 2004). Oilseed rape crops and small wetland features (such as ditches) now provide most nesting places in farmland. Additional reference: Burton et al. (1999).
Corn Bunting Miliaria calandra– National population decline has exceeded 80%. Fewer birds now raise a second brood than in the past, reducing the seasonal production of young (Brickle & Harper 2002), but success per nesting attempt was recorded as slightly higher during the years of decline (Crick 1997; Siriwardena et al. 1998). Nest survival was lower in localities with little invertebrate chick food (owing to pesticide use), which led to chick starvation and predation (Brickle et al. 2000). Population decline in Schleswig-Holstein, Germany, was attributed to increased chick starvation (Busche 1989). Benefits from low-input spring-sown cereals (barley), associated weedy winter stubbles and wide field margins. Other references: Donald and Evans (1994), Brickle and Harper (1999), Crick (1997), Donald and Forrest (1995), Donald et al. (1994).
Turtle Dove Streptopelia turtur– Decline attributed to reduction of tall hedgerows used for nesting and weed-seeds used as food (Browne & Aebischer 2001). Increased nest success recorded during the years of decline (Siriwardena et al. 2000), but reductions in duration of breeding season and in total seasonal productivity (Browne & Aebischer 2001, 2003).
Skylark Alauda arvensis– Adverse habitat changes include loss of rough grassland, switch from spring-sown to autumn-sown cereals (which grow too tall for nesting in spring), and conversion of mixed farms to cereal or intensive grass monocultures (Chamberlain & Gregory 1999); food shortages involve summer insects and winter seeds (Jenny 1990, Odderskaer et al. 1997). Breeding densities tend to be higher in permanent grass and set-aside than in autumn-sown or spring-sown cereals (Poulsen et al. 1998; Wakeham-Dawson et al. 1998, Chamberlain et al. 1999a, Eraud & Boutin 2002); crops that do not favour breeding Skylarks, such as autumn-sown cereals and rape, have become increasingly prevalent in recent decades. Nest success was higher during the years of decline (Siriwardena et al. 2000), but several studies suggest reduction in the duration of the breeding season, because of earlier crop growth and lack of alternative habitat locally (a consequence of greater arable monoculture) (O’Connor & Shrubb 1986, Wilson et al. 1997, Chamberlain & Crick 1999). No information on possible change in mortality. Breeding densities and seasonal productivity increased following the provision of unsown patches (4-m squares at two per hectare) in autumn-sown cereal fields (Morris et al. 2004). Other references: Green (1978), Shläpfer (1988), Donald et al. (2001a, 2002), Robinson (2001), Pierce-Higgins and Grant (2002).
Meadow Pipit Anthus pratensis– In lowland, decline associated with loss of patches of rough grass. In upland, reduced breeding densities evident in heavily grazed, shorter swards (Vanhinsberg & Chamberlain 2001, Pierce-Higgins & Grant 2002). Intensive grazing of heather moorland encourages the replacement of heather by grass, which favours Meadow Pipits, whose densities decline under further grazing, which reduces sward height and diversity, and associated insect densities (Smith et al. 2001). No relevant data on demographic changes during the years of decline.
Yellow Wagtail Motacilla flava– Breeds in damp grassland and in dry sparsely vegetated arable land (Mason & Lyczynski 1980, Nelson 2001). Decline attributed to drainage and reductions in the area of damp grassland, and generally more intensive grassland management, and to change from spring-sown to autumn-sown crops. Decline most marked in pastoral regions (Chamberlain & Fuller 2001). No published information on possible change in reproductive or mortality rates, or on possible effects on population levels of events in African wintering areas. Yellow Wagtails have responded with increased breeding density to raised water levels in some grassland nature reserves. Additional references: Bradbury and Bradter (2004), Henderson et al. (2004).
Starling Sturnus vulgaris– Reduction of food supply caused by conversion of former grass to arable in eastern districts, and by more intensive management of grassland generally, leading to reduction in soil invertebrates, and also by reduction in the numbers of accessible feed-sites for farm stock. Reduced survival during the years of decline recorded for Britain, and reduced reproductive rate recorded in Finland (Tiainen et al. 1989). Other references: Feare (1994), Whitehead et al. (1995), Freeman et al. (2002).
Blackbird Turdus merula– Decline associated with loss of hedgerows and field boundaries, and land drainage which reduces food availability. In The Netherlands, the main demographic change was reduced annual survival (Dix et al. 1998). Increased breeding density and success followed various conservation measures (including predator control) at the Game Conservancy Trust's farm in Leicestershire (Stoate & Szczur 2001).
Song Thrush Turdus philomelos– Decline associated with loss of hedgerows and field boundaries, and land drainage, which reduces food availability. Main demographic cause assessed as reduced survival, especially in years of prolonged summer drought or winter frost (Baillie 1990, Thomson et al. 1997, Robinson et al. 2004), judged as sufficient in a population model to account for decline at the observed rate, without any concurrent change in reproduction (Robinson et al. 2004). However, in one study, the breeding season was shortened in a dry arable area, compared to a more mixed farming area, leading to reduction in seasonal production of young, also judged as sufficient to cause population decline (Peach et al. 2004). Increased breeding density and success followed various conservation measures (including predator control) at the Game Conservancy Trust's farm in Leicestershire (Stoate & Szczur 2001).
Lapwing Vanellus vanellus– Main adverse habitat change associated with the drainage of wet grassland (Fig. 2); also conversion of mixed farms to arable or ‘improved’ grass monocultures; change from spring-sown to autumn-sown cereals (which reduces the area of spring tillage, favoured for nesting); and increased stocking densities on grassland (which leads to more disturbance, nest predation and trampling) (Beintema & Muskens 1987, Baines 1988, 1989, Beintema 1988, Galbraith 1988, Shrubb 1990, Shrubb & Lack 1991, Hudson et al. 1994, Wilson et al. 2001, Hart et al. 2002). No change in annual survival during the years of decline (Peach et al. 1994), so reduced reproduction proposed as the demographic cause; and in some local populations annual production measured as insufficient to offset expected annual mortality (e.g. Galbraith 1988). Seasonal productivity lower on improved than on unimproved grassland, owing to fewer replacement clutches and poorer chick survival (Baines 1989). In some localities, single pairs and small groups are more vulnerable to egg predation than larger groups, owing to the reduced effectiveness of communal nest defence (Seymour et al. 2003). Lapwings have responded with increased breeding density to local reserve management and agri-environment schemes (Ausden & Hirons 2002, Bradbury & Allen 2003). Additional references: Baines (1988, 1989), Crick et al. (1998), Shrubb (1990), Henderson et al. (2001, 2003), Sheldon et al. (2004).
Snipe Gallinago gallinago– Main adverse habitat change is the drainage of wet tussocky grassland (e.g. Baines 1988). Even in some areas where birds still breed, the nesting season is shortened because the ground dries out earlier in the breeding season, leading to reduction in seasonal productivity (Green 1988a). Snipe have responded with increased breeding density to raised water levels in some grassland nature reserves but not in others (Ausden & Hirons 2002). Two count schemes gave conflicting results, BBS indicating an increase in recent years, and breeding wader surveys in meadows a steep decline. Additional reference: Crick et al. (1998).
Curlew Numenius arquata– Main adverse habitat change is the drainage of rough wet grassland (e.g. Baines 1988). High predation rates on eggs in some areas, such as Northern Ireland, where measured reproductive rates were too low to sustain populations and could account for recent rates of population decline (Grant et al. 1999). Fragmentation of habitats may also allow Foxes to search nesting places more efficiently. Other references: Berg (1992, 1994).
Redshank Tringa totanus– Main adverse habitat change is drainage of wet grassland (e.g. Baines 1988). On coastal saltmarsh, breeding densities declined more markedly during 1985–96 on sites that had experienced an increase in grazing pressure, from ungrazed/lightly grazed to moderately/heavily grazed, although some grazing by cattle was deemed beneficial to sward structure (Norris et al. 1998). Redshanks have responded with increased breeding density to raised water levels in some grassland reserves (Ausden & Hirons 2002).
Stone Curlew Burhinus oedicnemus– On arable land, management has entailed finding nests, and protecting them from farm machinery, and the provision (through an agri-environment scheme) of spring tillage for nesting (Aebischer et al. 2000). Other references: Green (1988b), Green and Griffiths (1994).
Corncrake Crex crex– Main decline attributed to earlier and mechanized grass cutting (Norris 1947), but drainage and intensive grass management has also removed much previously suitable nesting habitat (Stowe et al. 1993). One of the last remaining populations of Corncrake in Ireland is in the Shannon ‘callows’, where mowing is forced late by unregulated winter and spring flooding (Shepherd & Green 1994). Breeding success and breeding density in various areas increased in response to later and more careful grass cutting (Green & Stowe 1993, Green et al. 1997, Green 1999, Green & Gibbons 2000).
Grey Partridge Perdix perdix– Population decline has exceeded 85%. One of the most thoroughly studied species, with proposed mechanisms tested by experiment (Fig. 1, Potts 1986, Rands 1985, Potts & Aebischer 1995, Tapper et al. 1996). Other references: Green (1984), Bro et al. (2000).
Black Grouse Lyrurus tetrix– Heavy grazing of moorland habitat causes decline in food-plants (for full grown birds) and insects (for chicks) (Fig. 3; Baines & Hudson 1995, Baines 1996, Jenkins & Watson 2001). Local populations responded, with improved breeding success and breeding densities, to reduced grazing within the framework of an agri-environment scheme, and some also responded in the same way to predator control (Calladine et al. 2002, Warren & Baines 2004).
Red Grouse Lagopus l. scoticus– Predation by raptors (especially Hen Harriers Circus cyaneus) can cause substantial population decline (Redpath & Thirgood 1997), but because some raptors and other predators are controlled on most grouse moors, long-term declines in Red Grouse densities are more often associated with loss of heather through overgrazing (Redpath & Thirgood 1997, Jenkins & Watson 2001). High sheep numbers in some areas also raise the incidence of louping ill, which is often lethal to grouse, accounting for some local declines (Duncan et al. 1979, Hudson & Dobson 1991).
Barn Owl Tyto alba– Main adverse habitat change is the loss or overgrazing of rough grassland, which supports the main prey species, the Field Vole Microtus agrestis; also loss of nest-sites through hedgerow tree removal and ‘barn conversion’, and collapse of old, disused cottages, previously suitable (Shawyer 1987, Ramsden 1998, Newton 2002). Population assessments in 1982–85 and 1995–97 put national numbers at 4500 pairs and 4000 pairs, respectively, but numbers fluctuate greatly from year to year, and the two figures result from different methodology, so may not be comparable (Shawyer 1987, Toms et al. 2001). Has responded by increased density and breeding success to the fencing out of sheep from areas of grassland (as in afforestation projects), and by increased breeding density to the provision of nestboxes in areas with insufficient nest-sites (Newton 2002).
Sparrowhawk Accipiter nisus, Merlin Falco columbarius, Peregrine F. peregrinus – Main declines from late 1950s to early 1960s, associated with the heavy use of organochlorine pesticides (Fig. 4). Populations recovered in subsequent decades following progressive reductions in organochlorine use, and their replacement by less persistent insecticides (Newton 1979, 1986, Ratcliffe 1993, Newton et al. 1997, 1999). The Sparrowhawk has stabilized or may have been in regional decline since about 1994.
Kestrel Falco tinnunculus– As for Barn Owl, except that old buildings are much less important as nest-sites (Village 1990).