Nest site characteristics and Parental activity: effects on predation and cowbird parasitism in the Brown-and-yellow Marshbird

SVAGELJ, W. S.; FERNÁNDEZ, G. J.; MERMOZ, M. E.

Puyehue, Chile

Congreso; VII Neotropical Ornithological Congress; 2003

Neotropical Ornithological Society

Nest site and microhabitat characteristics (i.e. concealment, height, distance to neighboring nest, etc.) has been suggested to affect nest predation and cowbird parasitism risks. Also, activity at the nest could influence nest detection by predators and brood parasites. Nest defense could repel predators, but increased parent activity at any nesting stage could increase nest predation and parasitism. We assess if nest site characteristics affect predation and brood parasitism by cowbirds on Brown-and-yellow Marshbird (Pseudoleistes virescens) nests. Also, we assess if parent activity at the nest increase predation and brood parasitism. We compared the survival and parasitism rates of natural nests during egg stage with those of the same nests after nesting cycle was completed (removing then, the parental activity). We did not find a strong association between nest site characteristics and parasitism or predation. We found that parental activity did not affect the probability of nest predation nor the egg losses by cowbirds. Cowbirds pecked and broke eggs at unattended nests, but they rarely parasitized them. Then, parental activity at the nest do not appear to affect the nest detection nor to avoid egg losses by cowbirds, instead of the active nest defense that Brown-and-yellow Marshbird perform. However, cowbirds used parental activity to effectively parasite this host. No differences were found between survival rates of experimental and natural nests. Then, predators did not appear to use parental activity to localize Brown-and-yellow Marshbird nests.