The ecological role of Southern Caracaras (Caracara plancus) and Black-chested Buzzard-eagles (Geranoetus melanolecus) as long distance secondary seed dispersers

COSTAN, A.; SARASOLA, J.H.

Bariloche

Conferencia; I Worldwide Raptor Conference; 2013

Secondary seed dispersal is a multistep system affecting plant population dynamics that includes two or more dispersal processes increasing the distance over which seeds of plants may establish in new sites. Here we evaluated the trophic relationships between two raptor species, the Southern Caracara and the Black-chested Buzzard-eagle, and one non-raptor, the Eared Dove (Zenaida auriculata). We particularly assessed if this predator-prey interaction facilitates long distance dispersion of seeds of two plant species, the red grass (Amaranthus quitensis) and the annual bugloss (Lycopsis arvensis), in semiarid forest of central Argentina. We captured doves to sample seeds contained in their crops. We simultaneously collected pellets of the two raptors species and a control sample of seeds directly from plants. All seeds were examined for viability and germination. A total of 789 and 918, and 511 and 1834, red grass seeds and annual bugloss seeds were found in the pellets of caracaras (n = 83) and eagles (n = 98) respectively. The viability of seeds obtained from plants was 91% and 95%, with a germination rate of 87% and 57% for red grass and annual bugloss respectively. Viability and germination of seeds obtained from dove crops was 72% and 91%, and 41% and 45%, for red grass seed and annual bugloss, respectively. Red grass seeds found in the pellets of caracaras and eagles had a viability of 35% and 40%, and a germination of 34% and 38%, respectively. Annual borage showed a viability of 9% and 89%, and a germination of 7% and 14%, respectively. Our results indicate that though passage of seeds thought raptor?s guts may reduce germination and viability, raptors are able to disperse seeds of these two plant species, conferring to these raptor species an overlooked and key ecosystem function other than their role as top predators.