Population dynamics and Productivity of McCown's Longspur at Matador, Saskatchewan
Date
1971-12
Authors
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Publisher
ORCID
Type
Degree Level
Masters
Abstract
Organisms at the carnivore-omnivore level of an ecosystem, such
as birds, do not represent a significant amount of biomass because of the
inefficiency of energy transfer through the trophic levels of a natural
system. Relative to that which is stored by the autotrophs, secondary
consumer energy fixed as production is minimal. Nevertheless, secondary
producers do represent a flow of energy and exert a regulatory effect
on the system through the act of consuming.
Generally, the productivity of an organism can be regulated
through one or more causal pathways as outlined by Watt (1968). Natality,
the birth rate, is determined by the fecundity and fertility of the
species. Those organisms which are born are then subjected to mortality
as a result of predation and other causes. Individuals which escape
mortality produce biomass through increment during growth usually at
a rate specific to the species. Individual characteristics of a species
or group of organisms may add some specific means of productivity such as
the moult and growth of new feathers in birds.
These causal pathways can all be ultimately regulated by the
food energy available to the parent generation during reproduction and to
the offspring during growth. Lack (1968) in his concluding statement
on bird population theory, repeats that the availability of food for the
young and to lesser extent that available to the female combined with the
risks of predation are the most important factors in determining the
course of the evolution of breeding habits in birds.
This study was designed to grossly assess the production aspects
of the life history of McCown's Longspur (Rhynchophanes mccownii Baird)
as a secondary producer in the Matador grassland ecosystem and to determine
the factors which affect the causal patterns of production described
above. Within these terms of reference, habitat preference, density,
standing crop and biomass components of the adult population were
studied. The moult and rate of production of new feathers together with
the effect on body components were also considered. The major source
of productivity through reproduction and growth of offspring was quantified
together with the effects of natality, mortality, growth rate and the
availability and source of food energy.
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Degree
Master of Science (M.Sc.)
Department
Biology
Program
Biology