Generation time and temporal scaling of bird population dynamics.
Theoretical studies have shown that variation in density regulation strongly influences population dynamics, yet our understanding of factors influencing the strength of density dependence in natural populations still is limited. Consequently, few general hypotheses have been advanced to explain the large differences between species in the magnitude of population fluctuations. One reason for this is that the detection of density regulation in population time series is complicated by time lags induced by the life history of species that make it difficult to separate the relative contributions of intrinsic and extrinsic factors to the population dynamics. Here we use population time series for 23 bird species to estimate parameters of a stochastic density-dependent age-structured model. We show that both the strength of total density dependence in the life history and the magnitude of environmental stochasticity, including transient fluctuations in age structure, increase with generation time. These results indicate that the relationships between demographic and life-history traits in birds translate into distinct population dynamical patterns that are apparent only on a scale of generations.
Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. bernt-erik.sather@bio.ntnu.no
Bernt-Erik
BE
Saether
Russell
R
Lande
Steinar
S
Engen
Henri
H
Weimerskirch
Magnar
M
Lillegård
Res
R
Altwegg
Peter H
PH
Becker
Thomas
T
Bregnballe
Jon E
JE
Brommer
Robin H
RH
McCleery
Juha
J
Merilä
Erik
E
Nyholm
Wallace
W
Rendell
Raleigh R
RR
Robertson
Piotr
P
Tryjanowski
Marcel E
ME
Visser
D000375:Aging; D000818:Animals; D001717:Birds / Q000145:classification / Q000502:physiology*; D011157:Population Dynamics; D012098:Reproduction / Q000502:physiology; D013269:Stochastic Processes; D015996:Survival Rate; D013997:Time Factors