Action: Protect nests from ants
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A randomised, replicated and controlled study from the USA found higher fledging success from white-eyed vireo Vireo griseus nests protected from ants with a physical barrier and a chemical repellent, compared to control nests.
Several ant species including the red imported fire ant Solenopsis invicta, the big-headed ant Pheidole megacephala and yellow crazy ants Anoplolepis gracilipes have been introduced across the world and have often become invasive. Whilst too small to damage most adult birds, they can have severe impacts on chicks. Due to their huge numbers and adaptability eradication is rarely an option (although see ‘Control invasive ants on islands’). Therefore preventing them from accessing nests may be the best intervention.
Supporting evidence from individual studies
A randomised, replicated and controlled study in March-July 2006-7 in a grassland/oak-juniper woodland mosaic in Texas, USA (Campomizzi et al. 2009) found that 18 white-eyed vireo Vireo griseus nests, protected from red imported fire ants Solenopsis invicta with a physical barrier and a chemical repellent, had significantly higher fledging success than 26 unprotected nests (31% vs. 10%). The same effect was seen in 13 experimental and 14 control black-capped vireo V. atricapilla nests, but this difference (13% vs. 7%) was non-significant. The physical barrier was Tanglefoot – a gum resin that traps crawling insects, applied to the branch >25 cm from each nest; the repellent was Arinix™ spiral wrap – a permethrin releasing plastic wrapped around the branch on top of the Tanglefoot.