Plovers, invertebrates and invasive predators: aspects of the ecology of some island populations

  • James St Clair

Student thesis: Doctoral ThesisPhD


This thesis makes progress in two broad fields of research, descriptive ornithology and invasion ecology, based largely on fieldwork in the Falkland Islands. Populations of two little-studied South American waders, the Two-banded Plover Charadrius falklandicus and the Rufous-chested Dotterel Charadrius modestus, were monitored over a four-year period at a single island site: in chapters two, three and four this thesis presents information on the diel pattern ofincubation sharing by males and females of both species (the two species showed opposite diel sex-roles), data on morphology including sexual dimorphism (male-biased in both species), breeding systems data including estimates of mate fidelity, and for Two-banded Plovers, demographic estimates including annual survival rates of adults and hatching success of nests. These are among the first detailed studies of the breeding behaviour and life-histories of anysouthern South American waders. Concurrent with the single-site wader study, an inter-islandnatural experimental approach was used to investigate the effects of non-native mammalian predators, firstly on the expression of anti-predator behaviour in the Two-banded Plover (chapter five) and secondly on the relative abundance of populations of an endemic insect, the Falkland Camel Cricket Parudenus falklandicus (chapter six). The latter chapters both infer strong effects of non-native mammalian predators: firstly, Two-banded Plovers expressed much larger flushing distances in response to an approaching (human) stimulus at sites where feral cats Felis catus were present, although flushing distances were shorter when background exposure to humans was relatively high (I interpret these effects as generalisation and habituation respectively). Secondly, the relative abundance of Camel Crickets in a given habitat type was substantially higher in the absence of Norway Rats Rattus norvegicus, regardless of whether the rats were naturally absent orhad been deliberately eradicated. Following the apparently strong effect of rats on insects in the Falkland Islands, in chapter seven I use literature from other island groups to review the effects of invasive rodents on island invertebrate populations; I conclude that negative effects are widespread and non-randomly distributed among invertebrate species, with large invertebrates particularly susceptible to rodent impacts. Finally, in chapter eight, potentially productive areas for future research and synthesis are suggested.
Date of Award1 Jul 2010
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorTamas Szekely (Supervisor)

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