DOI: 10.5061/dryad.73n5tb302
title: Subpopulation contributions to a breeding metapopulation of migratory Arctic herbivores: Survival, fecundity, and asymmetric dispersal

description: Estimates of demographic parameters for lesser snow geese (Anser
 caerulescens caerulescens) have become critical to understand ecosystem
 change in northern Canada. Exponential increase in abundance has produced
 hyperdensities of these herbivores that can affect Arctic ecosystem
 stability through intense foraging. Increased and sustained marking of
 individually-identifiable lesser snow geese over their breeding
 distribution now permits joint estimation of local vital rates and
 movement probabilities among widely scattered subpopulations. We used
 multi-state models, including an unobservable state, with live captures
 from 5 subpopulations and dead recoveries to estimate annual probabilities
 of (i) survival, (ii) capture, (iii) reported mortality and (iv) movement
 to other subpopulations, as well as derived estimates for probabilities of
 site fidelity and harvest. Our dataset included 144,754 captures of
 139,177 lesser snow geese marked with metal legbands, from 2006 to 2015,
 of which 5,542 were recaptured near breeding sites and 9,709 were
 recovered dead in North America. The best model supported variation in
 survival by subpopulation and age, with additive effects of subpopulation,
 age and sex on movement probability. Male breeding dispersal was greater
 than by females, and juvenile geese were more likely to move than adults.
 Strong northeastward geographic asymmetry in the probability of breeding
 movement was consistent with an eastward shift in wintering distribution
 observed in hunter recoveries. Mean annual survival ranged from 0.79-0.94
 for adults, and 0.16-0.47 for juvenile geese, with a strong negative
 relationship between regional adult and juvenile survival. Harvest
 probabilities were all ≤ 0.03 for adult and ≤ 0.06 for juvenile geese,
 suggesting little influence from direct anthropogenic exploitation.
 Metrics for subpopulation persistence and contributions of each to the
 metapopulation suggested declines in all but one subpopulation, and a
 declining midcontinent population overall. Our study highlights the
 importance of all subpopulation demographic parameters as modulators of
 persistence at both local and range-wide population dynamics.
description: Geese were captured en masse either as goslings (Age: HY, Hatch
 Year) close to fledging or as geese with adult plumage (Age: AHY, After
 Hatch Year) from 2006 to 2015 in Canada's Arctic and Subarctic.
 Captures were with the use of a helicopter and ground crews to locate and
 guide target groups into portable corral traps. Geese were marked with
 metal legbands only, no neckbands, at each of 5 subpopulations.
 Subpopulations are QMG (State Q, Queen Maud Gulf), SOU (State S,
 Southampton Island), BAF (State B, Baffin Island), LPB (State L, La
 Perouse Bay), and JAM (State J, James Bay). Number of birds banded in each
 year for each subpopulation, as well as year of recovery of dead birds
 (2006-2016), were supplied by the Bird Banding Laboratory, Laurel,
 Maryland, USA. Recaptures of birds already marked with legbands at each
 subpopulation were recorded. Recaptures occurred only between years, so
 all recaptures were of adult (AHY) geese only, whether marked initially as
 goslings (HY) or adults (AHY). Encounter histories of
 139,177 were summarized in the Live-Dead format, with a pair of columns
 for each year. The first column in a pair denotes captures and the second
 column denoting dead recoveries within a year of captures. Captures in the
 first column of each pair were coded with the letter corresponding to the
 geographic state of capture (Q,S,B,L,J) , otherwise zero in not captured.
 Recoveries of dead geese in the second column of each pair were coded with
 a 1, otherwise zero if not recovered. The last four columns in
 "enchist2.inp" represent whether each capture hisotry was of an
 adult males (AM), adult female (AF), juvenile male (JM), or juvenile
 female (JF), respectively. An "unobservable state" was set as
 "U" when importing the encounter history as input data and
 selecting "Multi-state for Live and Dead Encounters" for Program
 MARK. An input data summary of the information in "enhist2.inp"
 can be found in the file "m-ARRAY.txt". Age
 structure in the global and other models was imposed in Program MARK with
 the Parameter Index Matrix (PIM) so that recoveries of birds marked as HY
 geese informed juvenile parameters, but also adult (AHY) parameters if
 recaptured or recovered as adults; sex was structured as a group effect
 (see file 3 "Parameter_Index_Matrix_(PIM)_from_
 Global_Model_(survival_parameters_only).JPG"). Additional constraints
 were imposed to model additive effects between age, sex, state using the
 Design Matrix (DM) of Program Mark (see file 4
 "Design_Matrix_(DM)_Top_Model.csv" as an example).
 Nonidentifiable paramaters resulted form situations where there
 were no captures of geese from which to estimate parameters.
 Nonidentifiable parameters were set to zero; these included male and
 female HY survival in states S and U, capture probabilies for all 4
 age-sex cohorts in state U, transition of male and female HY geese from
 state S, transition of male and female HY geese from state U, and reported
 mortality for male and female HY geese in States S and U.
description: In addition to the multi-state capture-recovery data set as input
 data for Program MARK (file 1 "enchist2.inp"), consult the
 survival portion of the Parameter Index Matrix (PIM) (file "Parameter
 Index Matrix (PIM) from Global Model (survival parameters
 only).JPG"), as well as further constraints imposed by manipulating
 the Design Matrix (DM) (file "Design Matrix (DM) Top
 Model.xlsx") for additional guidance.