Action: Use decoys to attract birds to safe areas
- Seven studies found that birds bred in areas where decoys (of birds or nests) were used to attract birds. Six of the studies used several interventions at once. Two studies from the USA found that least terns Sterna antillarum and herons were not attracted to new areas to breed when decoys were used.
- Five studies from North America and France and Spain found that more birds landed near decoys than in control areas.
- The two studies to compare decoy types found that three-dimensional models were better than two-dimensional ‘cut-outs’ and plastic models of birds were better than rag decoys.
As well as physically moving birds to safe areas (translocations, see separate intervention), it is possible to try and get birds to move of their own accord. Many birds nest colonially for protection and are attracted nesting areas with conspecifics. Using realistic decoys may therefore encourage birds to colonise new areas. A similar intervention is ‘Use vocalisations to attract birds to safe areas’.
Supporting evidence from individual studies
A controlled study in New Jersey, USA (Kotliar & Burger 1984), found that at one sand and shell island, 81% of 821 least tern Sterna antillarum landings between 19th and 25th May 1983 were in a 100 m2 plot with tern decoys and only 19% in a control plot (without decoys). The first three nests established on the island were within 3 m of a decoy and none of the first 28 nests was in the control plot. At another sand and shell beach, there were only 12 landings in the two study plots between 20th May and 6th June. No terns attempted to nest at the site.
A trial between 1983 and 1985 in Alabama, USA (Dusi 1985), found that no little blue herons Egretta caerulea or cattle egrets Bubulcus ibis were attracted to a 4 ha swamp which had decoys installed in it. Up to 15 herons and egrets of various species were observed perching or roosting at the site, but none nested. Between eight and 25 decoy herons and egrets were installed each summer and heron calls were broadcast during daylight hours (see ‘Use vocalisations to attract birds to safe areas’).
A study of an Atlantic puffin Fratercula arctica translocation programme in 1973-81 (Kress & Nettleship 1988) found that a puffin population was established in Maine, USA, after 774 puffin nestlings were translocated from Newfoundland, Canada, and decoys were used to help attract fledged birds back to the release site. This study is discussed in ‘Translocate individuals’.
A controlled study in mixed coastal habitats on Kauai, Hawaii, USA, between December 1982 and April 1983 (Podolsky 1990) found that Laysan albatrosses Phoebastria immutabilis (formerly Diomedea immutabilis) were more likely to land in a study site with albatross decoys than at a control site without decoys (5.2% of 1,300 flying albatrosses landing at the experimental site vs. 1.8% of 877 at the control site). In addition, albatrosses landed closer to decoys than would be expected by random. Three-dimensional models of albatross pointing towards the sky attracted more albatrosses to within 3 m than two-dimensional models and paired models attracted more birds than single models. Six decoys were placed (either singly or in pairs) in a 10 m circle at each study plot. This study also describes the effect of playing albatross vocalisations on albatross landings, discussed in ‘Use vocalisations to attract birds to safe areas’, but does not provide any data on breeding.
A replicated trial in 1990 at Lake Ontario, Canada (Dunlop et al. 1991), found that common terns Sterna hirundo successfully used four floating wooden rafts, each with six tern decoys on, the same season that they were installed. This study is discussed in detail in ‘Provide artificial nesting sites’.
A small trial in 1993-5 at the western end of Lake Ontario, Canada (Lampman et al. 1996), found that the number of Caspian terns Sterna caspia nesting on an artificial raft with eight tern decoys on increased from one pair in 1993 to 50 pairs in 1995. This study is discussed in detail in ‘Provide artificial nesting sites’.
A review of management at two coastal wetland sites in Bouches-du-Rhône, France and in Andalucia, Spain (Martos & Johnson 1996), found that no greater flamingos Phoenicopterus roseus used an artificial nesting island created in the French site for the first year. However, following the installation of 500 decoy nests (wicker baskets packed with mud), large numbers of flamingos used the site. When 350 extra decoys were added to another part of the island, flamingos colonised it, in preference to areas without decoys. In Spain, newly created nesting habitat was used, with flamingos showing a preference for areas with artificial nests, depressions and scattered broken eggshell. This study is also discussed in ‘Provide artificial nest sites’, ‘Manage water levels in wetlands’ and ‘Control predators not on islands’.
A before-and-after study in the upper St. Lawrence River, Canada (Blokpoel et al. 1997) found that a common tern Sterna hirundo colony was re-established when decoys as well as control of ring-billed gulls Larus delawarensis were used to try to attract birds. This study is discussed in ‘Reduce inter-specific competition for nest sites by removing or excluding competitor species’.
A small controlled trial on a shell and sand beach in northern North Island, New Zealand (Jeffries & Brunton 2001), found that New Zealand fairy terns Sterna nereis davisae (formerly S. antillarum) were significantly more likely to land in experimental plots with tern decoy models in, compared to control plots, with 80% of all landing episodes were in experimental plots. No data on reproduction were provided. All plots were 120 x 55 m and one of four plots had three decoy models in. The experimental plot was rotated each day for a total of 16 days. This study also describes the effect of using vocalisations to attract birds, discussed in ‘Use vocalisations to attract birds to safe areas’.
A before-and-after trial at a coastal site in Long Beach, California, USA (Crouch et al. 2002), reported the successful translocation of a black-crowned night heron Nycticorax nycticorax colony using (amongst other interventions) decoys to attract birds. This study is discussed in ‘Translocate individuals’.
A before-and-after study on two small islands in the Columbia River Estuary, Oregon, USA (Roby et al. 2002), found that an entire Caspian tern Sterna caspia colony (approximately 8,900 pairs) relocated from Rice Island to East Sand Island between 1999 and 2001. Movement was encouraged by placing 253-415 decoys each year, as well as several other interventions. This study is discussed in detail in ‘Move fish-eating birds to reduce conflict with fishermen’.
A randomised, replicated and controlled study on a wetland site in Florida in autumn 1997 (Crozier & Gawlik 2003) found that wading birds (mainly white ibis Eudocimus albus and herons, Ardeidae) were more attracted to ponds with white plastic flamingo decoys than to ponds with Texas rag decoys (91 x 91 cm white plastic sheet knotted and on a 122 cm dowel rod) or control ponds with no decoys. Ponds with Tyvek® bag decoys (envelopes stuffed with paper and mounted on a 122 cm dowel rod) were intermediate and not significantly different from the other treatments (approximately 3 birds/pond with flamingos vs. 1.8 birds/pond for Tyvek® bags, 0.6 birds/pond for Texas rag and 1.1 birds/pond for controls). These differences were due to differences in the behaviour of white wading birds – there were no significant differences for dark wading birds. Experiments were conducted over five days, with eight ponds used each day (two for each treatment).
- Kotliar N.B. & Burger J. (1984) The use of decoys to attract least terns (Sterna antillarum) to abandoned colony sites in New Jersey. Colonial Waterbirds, 7, 134-138
- Dusi J.L. (1985) Use of sounds and decoys to attract herons to a colony site. Colonial Waterbirds, 8, 178-180
- Kress S.W. & Nettleship D.N. (1988) Re-establishment of Atlantic puffins (Fratercula arctica) at a former breeding site in the Gulf of Maine. Journal of Field Ornithology, 59, 161-170
- Podolsky R.H. (1990) Effectiveness of Social Stimuli in Attracting Laysan Albatross to New Potential Nesting Sites. The Auk, 107, 119-124
- Dunlop C.L., Blokpoel H. & Jarvie S. (1991) Nesting rafts as a management tool for a declining common tern (Sterna hirundo) colony. Colonial Waterbirds, 14, 116-120
- Lampman K., Taylor M. & Blokpoel H. (1996) Caspian terns (Sterna caspia) breed successfully on a nesting raft. Colonial Waterbirds, 19, 135-138
- Martos M.R. & Johnson A.R. (1996) Management of nesting sites for greater flamingos. Colonial Waterbirds, 167-183
- Blokpoel H., Tessier G.D. & Andress R.A. (1997) Successful restoration of the Ice Island common tern colony requires on-going control of ring-billed gulls. Colonial Waterbirds, 20, 98-101
- Jeffries D.S. & Brunton D.H. (2001) Attracting endangered species to 'safe' habitats: responses of fairy terns to decoys. Animal Conservation, 4, 301-305
- Crouch S., Paquette C. & Vilas D. (2002) Relocation of a large black-crowned night heron colony in southern California. Waterbirds, 25, 474-478
- Roby D.D., Collis K., Lyons D.E., Craig D.P., Adkins J.Y. & Myers A.M. (2002) Effects of colony relocation on diet and productivity of Caspian terns. The Journal of Wildlife Management, 66, 662-673
- Crozier G.E. & Gawlik D.E. (2003) The use of decoys as a research tool for attracting wading birds. Journal of Field Ornithology, 74, 53-58