FORAGING BEHAVIOURAL ECOLOGY OF THE SUPERB LYREBIRD
| Posted: |
06/08/2021 |
| Author(s): |
Alan Lill |
Foraging was investigated in a Superb Lyrebird population in southern Victoria. Soil invertebrate
food resources were moderately patchily distributed and the fact that foraging effort and success varied
greatly spatially suggested that the birds located patches mainly by trial-and-error. The similarity of
the nestling's diet, the soil invertebrate fauna and probably the adult's diet, plus the high mean capture
rate of 14-18 prey per min foraging, indicated relatively unselective prey consumption by adult
lyrebirds. Soil invertebrate abundance exhibited no highly consistent seasonal pattern; however, it
showed some tendency to increase in summer and autumn when fledglings were being reared rather
than in spring during the period of nestling care. Foraging was probably energetically expensive
because >80% of foraging time was spent digging in soil at a mean rate of 78-84 foot movements
per min; only 5-8% of foraging time was spent walking or running at a low speed between excavation
sites which averaged < 2 m apart. Foraging lyrebirds followed both fairly straight and quite circuitous
routes, the latter being more common in the non-breeding season and resulting in intensive exploitation
of a localized area. The mean daytime defecation rate (approx. 3 per h) and faecal energy density
(8.54-9.28 kJ per g dry mass) indicated that the species probably has a slow gut passage rate, but
is highly efficient at assimilating energy from its diet. Lyrebirds' foraging ecology could make them
particularly susceptible to habitat fragmentation and to disturbance that increases the cost of digging.
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