Passage through bird guts increases germination rate and seedling growth in Sorbus aucuparia


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  • 1On the west coast of Norway, Turdus spp. (Thrushes) are important dispersal agents of Sorbus aucuparia L. (Rowan) seeds, and avian and mammalian gut treatment often alters seed germination characteristics. In the present study the effects of avian gut treatment on S. aucuparia seeds are described, with emphasis on subsequent seedling growth.
  • 2Seeds ingested by Turdus spp. and non-ingested control seeds were sown singly or multiply in soil, in pomes, or in bird droppings.
  • 3Defecated seeds were ≈9% heavier than control seeds, and seedling growth was faster from defecated seeds than controls. In addition, differences in the rate of seedling emergence were found, with seedlings from ingested seeds appearing first.
  • 4The increased growth may be due to seedlings emerging earlier from defecated seeds, giving them an extended growth period at a time of increasing day length.
  • 5We argue that factors such as seedling growth, rate of seedling emergence and seed mass, in addition to percentage seed germination, are important in determining seedling survival.