Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird

Downloaded 121 times.

Primary tabs

Peery, M. Z., Becker, B. H., & Beissinger, S. R. (2006). Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird. Ecological Applications, 16(4), 1516-1528.
PDF
Metadata
TitleCombining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird
AuthorsZ. Peery, H. Becker, R. Beissinger
AbstractIdentifying source-sink dynamics is of fundamental importance for conservation but is often limited by an inability to determine how immigration and emigration influence population processes. We demonstrate two ways to assess the role of immigration on population processes without directly observing individuals dispersing from one population to another and apply these methods to a population of Marbled Murrelets (Brachyramphus marmoratus) in California (USA). In the first method, the rate of immigration (i) is estimated by subtracting local recruitment (recruitment from within the population due to reproduction) estimated with demographic data from total recruitment (f; recruitment from within the population plus recruitment from other populations) estimated using temporal symmetry mark-recapture models developed by R. Pradel. The second method compares population growth rates estimated with temporal symmetry models (λ TS) and/or population growth rates estimated from counts of individuals over multiple sampling periods (λ C) with growth estimates from a stage-structured projection matrix model (λ M). Both λ TS and λ C incorporate all demographic processes affecting population change (birth, death, immigration, and emigration), whereas matrix models are usually constructed without incorporating immigration. Thus, if λ TS and λ C are ≥1 and λ M < 1, the population is sustained by immigration and is considered to be a sink. Using the first method, recruitment estimated with temporal symmetry models was high (f̂ = 0.182, SE = 0.058), the mean adult birth rate, as estimated using the ratio of juveniles to ≥1 year old individuals (observed during ship-based surveys) was low (b̄ A = 0.039, SE = 0.014), and immigration was 0.160 (SE = 0.057). Using the second method, murrelet numbers in central California were stable (λ C = 1.058, SE = 0.047; λ TS = 1.064, SE = 0.033), but were projected to decline 9.5% annually in the absence of immigration (λ M = 0.905, SE = 0.053). Our results suggest that Marbled Murrelets in central California represent a sink population that is stable but would decline in the absence of immigration from larger populations to the north. However, the extent to which modeled immigration is due to permanent recruitment or temporarily dispersing individuals that simply mask population declines is uncertain. © 2006 by the Ecological Society of America.
JournalEcological Applications
Date2006
Volume16
Issue4
Start page1516
End page1528
ISSN10510761
Subjectsbirth rate, conservation, demography, emigration, endangered species, growth rate, immigration, juvenile, mark-recapture method, population dynamics, population growth, recruitment, seabird, survey, animal, article, biological model, Charadriiformes, ecosystem, environmental protection, physiology, time, United States, Animals, California, Conservation of Natural Resources, Models, Biological, Time Factors, North America, Brachyramphus, Brachyramphus marmoratus
NoteCited By (since 1996):36 Marine Mammals, Birds & Turtles, CODEN: ECAPE

Bookmark

Bookmarks: