Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Action: Reduce conflict by deterring birds from taking crops using bird scarers Bird Conservation

Key messages

Read our guidance on Key messages before continuing

  • A controlled paired study in the USA found reduced levels of damage to almond orchards when American crow Corvus brachyrhynchos distress calls were broadcast, compared to the previous year. There were no decreases in control orchards.
  • A replicated study in Pakistan found that four pest species were less abundant when reflector ribbons were hung above crops, compared to when ribbons were not used.


Supporting evidence from individual studies


A controlled, paired study in central California, USA (Houk et al. 2002), found that two of three almond orchards with crow distress calls broadcast had reduced damage from American crows Corvus brachyrhynchos in 2003, compared to 2002, when broadcasts were not used. Damage reduced from 6.0 kg/ha to 1.1 kg/ha, and 18.2 kg/ha to 4.8 kg/ha. There was no change in three paired sites without broadcasts. Orchards were 16-30 ha in area and monitored in June-August. Broadcasting units were deployed at onset of crow damage until almond harvest (1 unit/1.6 ha; hung in trees at 1-2 m) throughout the orchard, moved to a new tree every two weeks, switched to a different call every 3-4 days, broadcast dawn to dusk, each 25 seconds long with approximately 12 min between calls.



A replicated two-month study (November-December) on agricultural land in Punjab, Pakistan (Hafeez et al. 2008), found that hanging reflector ribbons 65-100 cm above crops was a low cost technique that significantly decreased abundances of four main bird pest species (house crow Corvus splendens, ring-necked parakeet Psittacula krameri, common myna Acridotheres tristis and bank myna A. ginginianus) that heavily damage young wheat Triticum aestivum and maize Zea mays crops.


Referenced papers

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2019) Bird Conservation. Pages 141-290 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.