Table 5. Stochastic growth rates for six models projected over 20 yrs. Subscripts reflect different factors in the model (Sj = juvenile survival (age 0–2), S3-6 = annual survival for birds age 3–6 yrs, Sa = adult survival (age 7+ yrs), Pa = mean number of young fledged per pair, λ = intrinsic rate of increase, t = time in yrs). Effect is calculated as the difference in a scenario’s growth rate relative to the Gannet Islands baseline growth rate.

Site Scenario Hunting Fox Sj S3-6 Sa Pa λ Effect|
Gannet Islands Baseline (no hunting/foxes) - - 0.778 0.970 0.890 0.390 1.007±0.007 -
Current conditions Y Y 0.482 0.970 0.890 0.306 0.957±0.008 -0.050
Fox predation only - Y 0.778 0.970 0.890 0.306 0.990±0.007 -0.017
P during 1980–2002 Y Y 0.482 0.970 0.890 0.615§ 0.973±0.002 -
Machias Seal Island Current conditions - - 0.778 0.912 0.967 0.562 1.058±0.005 -

Juvenile survival estimate from Machias Seal Island (population not exposed to hunting).
Fox predation reduced annual productivity from 0.390–0.306 (see text for explanation).
§ Productivity (0.698 when foxes absent, 0.615 when present) for the Gannet Islands 1980–2002.
|Change in lambda for each scenario relative to the baseline.