Predation pressure on the hatching of the Kentish plover (Charadrius alexandrinus) in clutch protection projects: a case study in north Portugal

Abstract

Context The decline of Kentish plover (Charadrius alexandrinus) populations is related to a great variety of factors, including habitat loss, predators and human activities. In particular, predators have been identified as the main factor of low hatching success in many areas. However, few manipulative experiments have addressed this issue. Aims This study was designed to analyse the advantages, but also threats, of the protection measures commonly adopted in clutch protection programs. Methods Through camera traps, monitoring animal tracks and opportunistic observation we identified potential predators. Additionally, predation risk was assessed through simulated clutches. To improve hatching success, antipredator measures were adopted and their effectiveness analysed. Key results Our results show that under natural conditions, most simulated clutches will not complete the incubation period. Primary causes of hatching failure are predation, flooding, desertion and mechanical cleaning of the beaches, but another cause is accidental trampling. In this regard, protection measures greatly increased hatching success. Conclusions The use of clutch protection measures greatly increases hatching success in Kentish plovers. Nevertheless, protection measures are related to an increasing harassment of incubating adults, which could result in clutch desertion or adult predation. Implications Altogether, current results suggest that the efficiency of protection measures needs to be tested and adapted to each particular area; this is because there are a high number of correlated factors that might drastically affect the results in each case.