Competition for invertebrate food between the endangered Seychelles Magpie Robin and endemic skinks.
Loading...
Date
1998
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The endemic landbirds of the Seychelles granitic islands have suffered considerable losses due to
predation by introduced rats and cats and extensive habitat destruction. With less than 100
individuals, the Critically Endangered Magpie Robin Copsychus sechellarum Newton, faces the
greatest risk of extinction. Translocations to three predator-free islands, Aride, Cousin and
Cousine, have provided valuable opportunities for gaining insights into the ecology of the species.
Of particular interest are links between the Magpie Robin, endemic skinks Mabvya spp., ground-living invertebrates and seabird colonies.
Magpie Robin faecal pellet and skink gut content analysis demonstrated a high degree of dietary
overlap between the species. A widespread exotic cockroach Pycnoscelus indicus was the
favourite prey item for each species. However, behavioural observations and a dietary choice
experiment indicated that there is no significant competition for food during the main seabird
breeding season. Invertebrate sampling on Cousine identified 52 species which were available in
all habitat types currently in use or those considered suitable for the Magpie Robin. Seabird and
skink density counts on Cousine demonstrated the considerable magnitude of vertebrate organic
food also available. Invertebrate sampling results on Cousin and Cousine were used to determine
territory quality and the carrying capacity of each island for the Magpie Robin.
While most seabirds are not breeding, skink survival depends on invertebrate abundance. M.
wrightii weight declined throughout this period but that of M. sechellensis remained fairly stable.
The data were insufficient to conclude that inter-specific competition for food exists between M.
sechellensis and the Magpie Robin during this period. Further expansion of the Magpie Robin
population depends on eradicating mammalian predators from other islands and maximising the
potential carrying capacities of those already supporting the species.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.
Keywords
Birds--Seychelles., Copsychus., Skinks., Species competition., Theses--Entomology.