DOI: 10.5061/dryad.wh70rxwm0
title: The demographic contributions of connectivity versus local dynamics to population growth of an endangered bird

description: 1. Conservation and management increasingly focus on connectivity, because
 connectivity driven by variation in immigration rates across landscapes is
 thought to be crucial for maintaining local population and metapopulation
 persistence. Yet, efforts to quantify the relative role of immigration on
 population growth across the entire range of species and over time have
 been lacking. 2. We assessed whether immigration limited local and
 range-wide population growth of the endangered snail kite (Rostrhamus
 sociabilis) in Florida, USA, over 18 years using multi-state, reverse-time
 modeling that accounts for imperfect detection of individuals and
 unobservable states. Demographic contributions of immigration varied
 depending on the dynamics and geographic position of the local
 populations, were scale-dependent, and changed over time. 3. By comparing
 the relative contributions of immigration versus local demography for
 periods of significant change in local abundance, we found empirical
 evidence for a disproportionately large role of immigration in
 facilitating population growth of a centrally-located population—a
 connectivity ‘hub’. The importance of connectivity changed depending of
 the spatial scale considered, such that immigration was more important
 driver of population growth at small versus large spatial scales.
 Furthermore, the contribution of immigration was much greater during time
 periods when local population size was small, emphasizing
 abundance-dependent rescue effects. 4. Our findings suggest that efforts
 aimed at improving local breeding habitat will likely be most effective at
 increasing snail kite population growth. More broadly, our results provide
 much needed information on the role of connectivity for population growth,
 suggesting that connectivity conservation may have the greatest benefits
 when efforts focus on centrally located habitat patches and small
 populations. Furthermore, our results highlight that connectivity is
 highly dynamic over time and that interpreting the effects of connectivity
 at local scales may not transfer to region-wide dynamics.
description: We used
 mark-resight data across the breeding range to interpret the role of
 immigration on population dynamics. From 1997 through 2015, multiple
 standardized band-resight surveys (4-6) were conducted during the peak of
 the snail kite breeding season (March 1 –June 30<sup>th</sup>)
 covering the entire known breeding range of the snail kite in Florida
 (Dreitz et al., 2002; Martin, Kitchens, & Hines, 2007; Reichert,
 Kendall, et al., 2016). During this time, 3,327 individually banded snail
 kites were resighted (7,232 total resights, of which 4,522 were in the
 northern region, 798 in Lake Okeechobee, and 1912 in the southern region).
 Of the total resighted individuals, 1,289 were banded before 1997, and
 first observed within this study as adults (&gt;1 year of age). From
 1997 to 2015, 2,888 snail kites were banded in the nest just prior to
 fledging (1,361 in the northern region, 252 on Lake Okeechobee, and 1,275
 in the southern region) and 45 were banded as adults (28 in the northern
 region, 3 in Lake Okeechobee, and 14 in the southern region).
description: This is a multi-state reverse-time
 robust band-resight datset for snail kites covering their entire breeding
 range in Florida from 2015-1997. "0" =
 non-detected,  "S" = snail kites resighted as adults (&gt;1
 year old) in the southern sub-population (south of Lake Okeechobee), 
 "R" = snail kites captured and banded as young (&lt;1 year
 old) in the southern sub-population (south of Lake
 Okeechobee), "K" = snail kites resighted as adults (&gt;1
 year old) in Lake Okeechobee,  "J" = snail kites captured and
 banded as young (&lt;1 year old) in Lake Okeechobee, "N" =
 snail kites resighted as adults (&gt;1 year old) in the northern
 sub-population (north of Lake Okeechobee),  "M" = snail kites
 captured and banded as young (&lt;1 year old) in the northern
 sub-population (north of Lake Okeechobee).  All years have 6 repeat survey efforts,
 except 2002 and 2003, which have 5 and 4, respectively.  To assess the role of immigration in
 maintaining local population growth, we compared the relative contribution
 of total immigration (adult and juvenile) versus the combined
 contributions of local adult survival (and fidelity) and local juvenile
 recruitment for each of the three local populations (northern region,
 southern region, and Lake Okeechobee).  We tested whether contribution
 parameters varied over time using AIC to compare the relative fit of a
 model with time-invariant contribution parameters to that of a model that
 allowed contributions to vary among years. All models were implemented
 using Program MARK 8.1 (White & Burnham, 1999), implemented using
 the R-package, RMark (Laake, 2013).