Investigating the relationships between Taylor's Power Law coefficients, demographic parameters, and population dynamics

Taylor’s power law (TPL hereafter) states that the variance of population size estimates is related to the mean population size by a simple power relationship, characterised by two coefficients, a and b. A long-term multi-species dataset on bird abundance was used to investigate the relationships between TPL coefficients, species demographic traits, habitat types, and also long-term trends in population dynamics. The relationships were investigated using a General Linear Model (GLM) framework. Comparison of TPL coefficients calculated from the first half of the long-term data  (1964-1982) and those calculated using the second half (1983-2000) showed surprisingly little correlation. There was also little correlation, within species, between b values calculated from plots occurring in different habitat types. These results raise concerns regarding the often-cited constancy of b. We show that the parameters of TPL can be related, to some degree, to life-history traits and we discuss the consequences of this for interpreting long-term spatio-temporal dynamics.