Efecto del tamaño de nidada y parasitismo de cría en la reducción de nidada en Pecho Amarillo, Pseudoleistes virescens.

DURÉ-RUIZ, NATALIA; M.E. MERMOZ; FERNÁNDEZ, G. J..

Buenos Aires

Congreso; XI Reunión Argentina deOrnitología; 2005

Asociación Ornitológica del Plata

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Brood parasitism usually imposes several costs to individual hosts. One of these costs is the increase of the probability of brood reduction. In this paper we analyzed the effect of cowbird parasitism on the probability of brood reduction in the Brown-and-yellow Marshbird, a common host in the Argentinean Pampas. By using a nine-year database of nesting success of Brown-and-yellow Marshbirds, we compared the number of host fledglings produced and assessed the effect of year, parasitism; overall brood size; and hatching delay  onthe probability of brood reduction. Parasitized and unparasitized nests had a similar host clutch size, but parasitized nest produced less number of Brown-and-yellow Marshbird fledglings. About 25 % of nests suffered brood reduction, with most of them parasitized by cowbirds (68 %). Hatching delay was the main factor associated to brood reduction in this species. It was associated to number of cowbird eggs present in the nest and overall brood size. The results we obtained reinforces the idea that cowbird egg laying synchronization impose additional costs to host as it increase the probability of host brood reduction.