Use legislative regulation to protect wild populations
- Six out of seven before-and-after studies and two literature reviews/meta-analyses found evidence that legislation protects bird populations.
- Five studies in Europe, Indonesia and across the world found increased population levels of vultures, raptors, cranes and cockatoos following protective legislation (amongst other interventions). However, one found populations of raptors declined soon after. The literature review also found two cases of limited or no impact of legislation.
- Two before-and-after studies from Denmark and the USA and Canada and the meta-analysis found increased estimated survival of falcons, ducks and parrots with stricter protection, but not necessarily population-level responses.
- A meta-analysis found decreased harvest of parrots in areas with stricter protection regimes, but a before-and-after study found no evidence for reduced shearwater harvest with legislation.
Perhaps the most commonly used intervention in response to declining species is to provide legal protection for the species. This alone may be enough to protect a species or population, but if not, de facto or ‘on-the-ground’ protection may also be required to ensure people abide by the law.
A before-and-after study examining 524 kestrels Falco tinnunculus recovered during 1917-80 in Denmark (Noer & Secher 1983) found that estimated survival rates of birds ringed as chicks increased during 1967-72 (66% annual survival) compared to 1945-66 (50%), following the introduction of legal protection for all birds of prey in 1967. However, the increase in survival rate following kestrel-specific legislation in 1926 was insignificant (45% for 1917-25 vs. 55% for 1926-39) and there was a significant fall in 1973-80 (to 53%). There were similar (although insignificant) patterns for birds ringed as juveniles or adults. There were significant decreases in the proportion of recoveries that were shot following each piece of legislation, from 1917-25 (59% of 29) to 1926-39 (14% of 35) and again from 1945-66 (17% of 76) to 1976-80 (2% of 192).
A before-and-after study at non-commercially exploited short-tailed shearwater Puffinus tenuirostris colonies in Tasmania, Australia (Skira et al. 1986), found that attempts to reduce non-commercial harvests of shearwater chicks in 1979 did not reduce the percentage of chicks taken, which remained at over 90% until 1985. Legal measures included shortening the non-commercial harvest season (so that it ended in mid- not late-April), reducing the daily bag limit, closing colonies on rotation, protecting colonies, education and stricter regulation enforcement. Takes at the time of the study were considered to be well in excessive of the maximum sustainable yield at the colonies.
A before-and-after study in the western Pyrenees, Spain (Donazar & Fernandez 1990), found that the population of griffon vultures Gyps fulvus increased from 282 pairs (in 23 colonies) in 1969-75 to 1,097 pairs (46 colonies) in 1989 following the initiation of multiple conservation interventions including: legal protection (in 1973); the creation of a reserve at nine breeding colonies (one in 1976, eight in 1987); the banning of strychnine (in 1984); and the installation of feeding stations between 1969 and 1979. Surveys in 1979 and 1984 found 364 pairs (in 26 colonies), and 589 pairs (32 colonies) respectively. This study is also discussed in ‘Habitat protection’, ‘Restrict certain pesticides or other agricultural chemicals’ and ‘Provide supplementary food to increase adult survival’.
A 1998 literature review of crane Grus spp. conservation (Davis 1998) described how two of four case studies found a positive response of crane populations to legal protection, with one showing partial success and the final study finding that legal protection had no impact. A small population of red-crowned cranes G. japonensis remained stable and increased slightly (from 20 to 35 birds between 1925-52) following legal protection at Kushiro Marsh, Hokkaido, Japan; whilst the American population of migratory sandhill cranes G. canadensis increased dramatically following a ban on hunting. Whooping cranes G. americana continued to decline following protection in 1916, but after public education, only four birds are thought to have been shot (see ‘Use education programmes and local engagement to help reduce pressures on species’). The central Asian population of Siberian cranes G. leucogeranus continued to decline in India, from 200 in 1964-5 to three in 1996-7 despite protection in flyways in Pakistan. This study is also discussed in ‘Habitat protection’, ‘Use education programmes and local engagement to help reduce pressures on species’, ‘Mark power lines to reduce incidental mortality’, ‘Provide supplementary food to increase adult survival’ and ‘Release captive-bred individuals’.
A before-and-after study in six areas in Canada and the USA (Francis et al. 1998) found that (for areas with more than 100 ducks recovered), the introduction of progressively more restrictive legislation on harvesting American black ducks Anas rubripes in 1967 and 1983 (USA) and 1984 (Canada) appeared to reduce hunting mortality: recovery rates of ringed ducks fell by 14.5% (adults) and 7% (immatures) from 1955-66 to 1967-82 and by 37% (adults) and 27% (immatures) from 1967-82 to 1983-93. Models calculating survival rates, however, estimated that these changes would not necessarily see a corresponding increase in survival.
A before-and-after study on Sumba, Indonesia (Cahill et al. 2006), found that estimated population densities of citron-crested cockatoos Cacatua sulphurea citrinocristata increased between 1992 and 2002, following the imposition of a ban on trade in wild-caught birds in 1993. Increases were seen over the entire study and at two out of four forest sites (by 130-700%). One further site showed no change in density and the final site a possible decrease. No evidence was found for forest contraction (i.e. increased densities are thought to reflect an increase in total population sizes), total recorded birds increased by 56% from 1992-2002; significantly more birds were in groups of two or more and the estimated population size was 90% larger in 2002. The authors note that the trade ban has not been enforced perfectly, but that it has significantly reduced the number of wild-caught birds being traded.
A literature review and meta-analysis (Pain et al. 2006) found that protective legislation reduced nest-take (the percentage of nests from which chicks were removed by people) in wild parrots and may increase nest success. Across 20 species-country combinations, medium (involving either national or local protection) and high (involving both) levels of protection significantly reduced nest-take between 4.5 and 50 times compared to low levels of protection (unenforced, ambiguous or absent local or national protection). These results excluded a Nigerian study based on trapper surveys and with 100% nest-take, but included Australian data – Australia being the most developed country in the analysis and with a disproportionate number of studies. If both countries were excluded then medium and high protection resulted in a significant (170%) increase in nest success. However, if all data were included then there was a non-significant increase in nest success.
A before-and-after study on a grouse moor in Dunfries and Galloway, south Scotland (Baines et al. 2008), found that the numbers of hen harriers Circus cyaneus and peregrine falcons Falco peregrinus increased after birds were given full protection from persecution in 1990 (harriers increased from two pairs in 1992 to 20 pairs in 1997, whilst peregrines increased from two to six pairs). However, following the discontinuation of moor management in 2000, harriers declined again to two to four pairs in 2003-6 (see ‘Shrubland modifications - Use fire suppression or control’). Both species were legally protected since 1961, but until 1990 many were still killed illegally on the moor. Three wader species and red grouse Lagopus lagopus all declined following harrier protection and the cessation of management. Meadow pipits Anthus pratensis and stonechats Saxicola rubicola both declined as harriers increased but increased again after 2000. Carrion crows Corvus corone increased from 2000, after they were no longer shot by gamekeepers.
A controlled, before-and-after study from 1970-2000 across Europe (Donald et al. 2007) found that target bird species appeared to benefit from the passing of the EU Birds (79/409/EEC, est. 1979) and Habitats (92/43/EEC, est. 1992) Directives. This study is discussed in ‘Habitat protection – Legally protect habitats’.
- Noer H. & Secher H. (1983) Survival of Danish kestrels Falco tinnunculus in relation to protection of birds of prey. Ornis Scandinavica, 14, 104-114
- Skira I.J., Wapstra J.E., Towney G.N. & Naarding J.A. (1986) Conservation of the short-tailed shearwater Puffinus tenuirostris in Tasmania, Australia. Biological Conservation, 37, 225-236
- Donázar J.A. & Fernández C. (1990) Population trends of the griffon vulture Gyps fulvus in Northern Spain between 1969 and 1989 in relation to conservation measures. Biological Conservation, 53, 83-91
- Davis C. (1998) A review of the success of major crane conservation techniques. Bird Conservation International, 8, 19-29
- Francis C.M., Sauer J.R. & Serie J.R. (1998) Effect of restrictive harvest regulations on survival and recovery rates of American black ducks. The Journal of Wildlife Management, 62, 1544-1557
- Cahill A.J., Walker J.S. & Marsden S.J. (2006) Recovery within a population of the Critically Endangered citron-crested cockatoo Cacatua sulphurea citrinocristata in Indonesia after 10 years of international trade control. Oryx, 40, 161-167
- Pain D.J., Martins T.L.F., Boussekey M., Diaz S.H., Downs C.T., Ekstrom J.M.M., Garnett S., Gilardi J.D., McNiven D., Primot P., Rouys S., Saoumoe S., Symes C.T., Tamungang S.A. & Theuerkauf J. (2006) Impact of protection on nest take and nesting success of parrots in Africa, Asia and Australasia. Animal Conservation, 9, 322-330
- Baines D., Redpath S., Richardson M. & Thirgood S. (2008) The direct and indirect effects of predation by Hen Harriers Circus cyaneus on trends in breeding birds on a Scottish grouse moor. Ibis, 150, 27-36
- Donald P.F., Sanderson F.J., Burfield I.J., Bierman S.M., Gregory R.D. & Waliczky Z. (2007) International conservation policy delivers benefits for birds in Europe. Science, 317, 810-813