A model of northern pintail productivity and population growth rate
Authored by PL Fling, JB Grand, RF Rockwell
Date Published: 1998
DOI: 10.2307/3802565
Sponsors:
United States Geological Survey (USGS)
Platforms:
No platforms listed
Model Documentation:
Other Narrative
Flow charts
Mathematical description
Model Code URLs:
Model code not found
Abstract
Our objective was to synthesize individual components of reproductive
ecology into a single estimate of productivity and to assess die
relative effects of survival and productivity: on population dynamics.
We used information on nesting ecology, renesting potential, and
duckling survival of northern pintails (Anas aouta) collected on the
Yukon-Kuskokwim Delta (Y-K Delta), Alaska, 1991-95, to model the number
of ducklings produced under a range of nest success and duckling
survival probabilities. Using average values of 25\% nest success, 11\%
duckling survival, and 56\% renesting probability from our study
population, we calculated that all young in our population were produced
by 13\% of the breeding females, and that early-nesting females produced
more young than later-nesting females. Further, we calculated, on
average, that each female produced only 0.16 young females/nesting
season. We combined these results with estimates of first-year and adult
survival to examine the growth rate (lambda) of the population and the
relative contributions of these demographic parameters to that growth
rate. Contrary to aerial survey data, the population projection model
suggests our study population is declining rapidly (lambda = 0.6969).
The relative effects ori population growth rate were 0.1175 for
reproductive success, 0.117.5 for first-year survival, and 0.8825 for
adult survival. Adult survival had the greatest influence on lambda for
our population, and this conclusion was robust over a range of survival
and productivity estimates. Given published estimates of annual survival
for adult females (61\%), our model suggested nest success and duckling
survival need to increase to approximately.40\% to achieve population
stability. We discuss reasons for the apparent discrepancy in population
trends between our model and aerial surveys in terms of bias in
productivity and survival estimates.
Tags
Survival
Alaska
Yukon-kuskokwim delta
Nest success