NEST MONITORING DOES NOT INCREASE NEST PREDATION IN OPEN-NESTING SONGBIRDS: INFERENCE FROM CONTINUOUS NEST-SURVIVAL DATA

Abstract

Abstract The disturbance associated with nest monitoring raises concerns about the validity of the estimated nest success and the well-being of the populations under study. Observer activity may attract or deter predators to or from bird nests, thus decreasing or increasing nest success. Results of previous studies related nest success to frequency of nest visits or estimated survival over rechecking intervals of different length. Such studies usually cannot reveal the underlying mechanism through which predation rate is influenced, because the timing of predation remains unknown. I measured, using data loggers, the exact survival times of 747 nests of 11 songbird species in fragmented woodland in the Czech Republic in 2001–2003 and analyzed the temporal relationship between predation and observer visits. I found only a short-term observer effect that lowered the hazard of predation during 2 h after a visit but did not appreciably affect the overall nest success. The timing of nest visits and the short du...