Action: Use vocalisations to attract birds to safe areas
- Six studies from North America, the Galapagos and the Azores found that seabirds were more likely to nest in areas where vocalisations were played, or were successfully attracted to nest in new areas, following the playing of vocalisations. Four of these studies used several interventions at once. One study found that some calls were more effective than others.
- Two studies from the USA and the Galapagos found that birds did not colonise all new areas where vocalisations were played. It is possible that the result from the Galapagos was due to only having a single year’s data.
- One controlled study from Hawaii found that albatross were more likely to land in areas where vocalisations were played than in areas without vocalisation playback. A small controlled study from New Zealand found that terns were not more likely to land in areas where vocalisations were played.
As well as physically moving birds to 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 to areas with conspecifics. Especially for birds that land mainly at night, hearing the calls and other vocalisations of conspecifics may be an important part of guiding them to colonies. Playing recordings of these calls may therefore encourage birds to colonise new areas. A similar intervention is ‘Use decoys to attract birds to safe areas’.
Supporting evidence from individual studies
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 heron calls broadcast from it. Up to 15 herons and egrets of various species were observed perching or roosting at the site, but none nested. The calls were played on a continuous loop, every three minutes during daylight hours over the summer, and decoys were also installed (see ‘Use decoys to attract birds to safe areas’).
A replicated, controlled study in 1980-3 on four islands in Maine, USA (Podolsky & Kress 1989), found that significantly more Leach’s storm petrels Oceanodroma leucorhoa colonised artificial nest chambers when the petrel’s ‘purr’ call was played from speakers near the burrows, compared to when only the ‘chuckle’ call was played or control burrows, where no vocalisations were played (24% of 40 burrows with just ‘purr’ calls colonised and 17.5% of 164 burrows with ‘purr’ and ‘chuckle’ calls vs. 0% for 20 burrows with ‘chuckle’ only and 0% for 40 control burrows). Calls were played from 22:00 hours until 04:00 each night from mid-May to mid-August from speakers located in the centre of clusters of burrows. Burrows that were colonised were significantly closer to speakers than expected at random, with over 80% of occupied burrows within 1.5 m of a speaker. Overall, only two chicks fledged successfully from 264 artificial burrows over three years (both in the third year). This study is also discussed in ‘Provide artificial nesting sites’.
A controlled study on Kauai, Hawaii, USA, between December 1982 and April 1983 (Podolsky 1990) found that Laysan albatrosses Phoebastria immutabilis were more likely to land in a study site with albatross decoys on days when albatross vocalisations were also played, than on days when vocalisations were not played or than at a control site with neither decoys nor vocalisations (8.2% of 1,053 flying albatrosses landing when vocalisations were playing vs. 5.2% of 1,300 without vocalisations and 1.8% of 877 at the control site). Albatrosses were also more likely to land close to speakers when vocalisations were playing, compared to when they were turned off (76% of the 97 closest landings when speakers were on vs. 24% when they were off). Each study plot had a speaker surrounded by six decoys. The effect of the decoys in attracting albatrosses is discussed in ‘Use decoys to attract birds to safe areas’.
A before-and-after study on two islands in the Galapagos, Ecuador (Cruz & Cruz 1996), found that playing dark-rumped petrel Pterodroma phaeopygia phaeopygia vocalisations from loudspeakers in 1988-90 successfully attracted petrels to an area on Santa Cruz Island provided with artificial burrows, but that playing similar recordings on the predator-free island of Pinta failed to attract any petrels in 1991. The role of artificial burrows in this study is discussed in ‘Provide artificial nesting sites’, and predator control in ‘Control mammalian predators on islands’.
A small trial in 1993-4 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 increased from one pair in 1993 to six pairs in 1994. A speaker system played vocalisations from a Caspian tern colony for four hours a day as terns arrived in the area each year. The study is discussed in detail in ‘Provide artificial nesting sites’.
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 no more likely to land in experimental plots on eight days when a tape of fairy tern calls was played, compared with eight days when calls were not played. 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 the decoys on bird behaviour, discussed in ‘Use decoys 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) vocalisations of the original colony. 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 using between two and for audio systems, broadcasting the sounds of a Caspian tern colony, as well as several other interventions. This study is discussed in detail in ‘Move fish-eating birds to reduce conflict with fishermen’.
A study in 2000-1 on an islet in the Azores, Portugal (Bolton et al. 2004), found that artificial nest chambers occupied by Madeiran storm petrels Oceanodroma castro were significantly closer to speakers playing the petrels’ ‘nest song’ every night than unoccupied nest chambers. Forty-seven of 115 chambers were used in early 2000; with 40 of 147 used in September 2000 and 49 in 2001. This study is discussed in more detail in ‘Provide artificial nesting sites’.
A before-and-after study on Mana Island, North Island, New Zealand (Miskelly & Taylor 2004), found that a new nesting colony of common diving petrels Pelecanoides urinatrix was established by playing vocalisations, providing artificial nesting burrows and translocating chicks. This study is discussed in ‘Translocate individuals’, ‘Provide artificial nests’ and ‘Artificially incubate and hand-rear birds in captivity’.
- Dusi J.L. (1985) Use of sounds and decoys to attract herons to a colony site. Colonial Waterbirds, 8, 178-180
- Podolsky R.H. & Kress S.W. (1989) Factors affecting colony formation in Leach's storm-petrel. The Auk, 106, 332-336
- Podolsky R.H. (1990) Effectiveness of Social Stimuli in Attracting Laysan Albatross to New Potential Nesting Sites. The Auk, 107, 119-124
- Cruz J.B. & Cruz F. (1996) Conservation of the dark-rumped petrel Pterodroma phaeopygia of the Galápagos Islands, 1982-1991. Bird Conservation International, 6
- Lampman K., Taylor M. & Blokpoel H. (1996) Caspian terns (Sterna caspia) breed successfully on a nesting raft. Colonial Waterbirds, 19, 135-138
- 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
- Bolton M., Medeiros R., Hothersall B. & Campos A. (2004) The use of artificial breeding chambers as a conservation measure for cavity-nesting procellariiform seabirds: a case study of the Madeiran storm petrel (Oceanodroma castro). Biological Conservation, 116, 73-80
- Miskelly C.M. & Taylor G.A. (2004) Establishment of a colony of common diving petrels (Pelecanoides urinatrix) by chick transfers and acoustic attraction. Emu, 104, 205-211