A neglected cost of brood parasitism: egg punctures by shiny cowbirds during inspection of potential host nests

VIVIANA MASSONI; JUAN CARLOS REBOREDA

THE CONDOR

The Cooper Ornithological Society

Año: 2002 vol. 104 p. 407 - 412

0010-5422

Parasitized hosts of the Shiny Cowbird (Molothrus bonariensis) suffer several costs, and among the most important is the loss of eggs through egg punctures inflicted by the parasite. Unparasitized nests also have eggs damaged by cowbirds, but researchers usually ignore these losses. To quantify this cost we compared three groups of nests of the Yellow-winged Blackbird (Agelaius thilius): parasitized and unparasitized nests from an area used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. costs, and among the most important is the loss of eggs through egg punctures inflicted by the parasite. Unparasitized nests also have eggs damaged by cowbirds, but researchers usually ignore these losses. To quantify this cost we compared three groups of nests of the Yellow-winged Blackbird (Agelaius thilius): parasitized and unparasitized nests from an area used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. costs, and among the most important is the loss of eggs through egg punctures inflicted by the parasite. Unparasitized nests also have eggs damaged by cowbirds, but researchers usually ignore these losses. To quantify this cost we compared three groups of nests of the Yellow-winged Blackbird (Agelaius thilius): parasitized and unparasitized nests from an area used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. Molothrus bonariensis) suffer several costs, and among the most important is the loss of eggs through egg punctures inflicted by the parasite. Unparasitized nests also have eggs damaged by cowbirds, but researchers usually ignore these losses. To quantify this cost we compared three groups of nests of the Yellow-winged Blackbird (Agelaius thilius): parasitized and unparasitized nests from an area used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism. Agelaius thilius): parasitized and unparasitized nests from an area used by Shiny Cowbirds, and unparasitized nests from an area not used by the parasite. Because cowbirds puncture eggs as soon as the first host eggs are laid, we calculated the clutch size only for those nests found during construction. Unparasitized nests in the area used by cowbirds had lower egg survival rate and hatching success and higher probability of nest desertion than unparasitized nests in the cowbird-free area. Our results indicate that one must consider egg punctures at unparasitized nests to avoid underestimating the impact of parasitism.