Can seed-eating birds spread viable canola seed?

Abstract

The potential for seed-eating birds to disperse viable canola (Brassicaceae: Brassica napus) seeds and establish feral populations or disperse genetically modified cultivars was investigated in captive feeding trials determining the: 1) acceptability of canola as food, 2) passage time of canola through the gut (PT), and 3) viability of passed seed. Four dove/pigeon, one finch, and two duck species were tested. Only Crested Pigeons Ocyphaps lophotes and some Wood Ducks Chenonetta jubata ate canola seed in significant amounts in the presence of other food. Over 460 faecal pellets were examined for the presence of whole/viable seed, but only seven pellets (~1.5%), all from Wood Ducks, contained whole seed. Of the 11 passed seeds (represents <0.01% of seed ingested by these ducks), only five germinated successfully (cf. 50 of 50 control seeds). Mean passage time of seed was quick for most species, ranging from 0.5 h in Senegal Doves, Streptopelia senegalensis, 1.3 h in Bronzewing Pigeons, to 2-3 h in the ducks C. jubata, and Anas superciliosa. This suggests that potential seed dispersal distances via these birds may generally be short (<10 km). Although the passage of viable diaspores was rare, the large number of birds likely to be feeding on canola seed in agricultural fields or at spillages on roadsides and loading zones suggests there is the potential for birds to disperse viable canola seed, including viable seed from genetically modified canola crops. Management options such as avoiding large piles of spilt seed or storing canola seed near watercourses would minimize this risk. However, the eradication of any established feral herbicide-resistant GM-canola plants could remain problematical.