Abstract

The number of black brant Branta bernicla nigricans nests within major breeding colonies on the Yukon-Kuskowkim Delta has declined since 1992. It has been hypothesized that these declines are partially explained by increased numbers of black brant breeding outside of these colonies. To assess this hypothesis, we analyzed spatiotemporal patterns in numbers of black brant nests occurring outside major colonies. Nesting densities of black brant vary among three strata: 1) peripheral to major colonies, 2) other coastal habitats, and 3) inland habitats. We sampled some substrata within each stratum type only between 1986 and 1999 (historical strata), whereas we sampled others over the period 1986–2016 (long-term strata). We fit regression models with number of nests on a plot as a response variable, a log link, and year as the explanatory variable. We allowed each stratum (e.g., historical peripheral) to have its own intercept to account for variation in mean nest density but constrained linear and quadratic regression coefficients to be the same for strata in similar habitats (e.g., historical and long-term peripheral). We used a negative binomial distribution for nests to allow for substantial variation in nests per plot. We fit models using Markov Chain Monte Carlo methods in JAGS. Ninety-five percent credible intervals for both linear and quadratic coefficients for the peripheral and coastal strata, where most nests occurred, broadly overlapped zero, indicating modest trends in numbers of nests in these strata. We estimated there were 6,584 (95% credible interval: 4,221−11,269) dispersed nests in 1986, increasing to 11,051 (95% credible interval: 7,450−17,460) in 2016. Our results indicated that increases in dispersed nests were unable to replace declines in colony nests. Furthermore, quadratic trends indicated that potential earlier annual increases in dispersed nests have declined to zero. We conclude that total numbers of black brant nests on the Yukon-Kuskokwim Delta are likely declining, consistent with the trend in fall age ratios over the same period. Uncertainty about trends in areas not sampled since 1994 adds to the uncertainty about the precise magnitude of the decline. We recommend that the area sampled by the random plot program be expanded to include strata sampled only before 1995.

Introduction

Spencer et al. (1951) described black brant Branta bernicla nigricans as nesting continuously over much of the coastal zone of the central Yukon-Kuskokwim Delta (YKD), Alaska, and the presence of a high-density concentration (colony) of nesting black brant near the mouth of the Kashunuk River has been known since at least 1924 (Dufresne 1924; Olson 1951). By 1981, the presence of four major colonies, Baird Inlet, Kigigak Island, Tutakoke River, and Kokechik Bay, was known. Sampling in 1981 and 1982 (Byrd and Smith 1981; Byrd et al. 1982) estimated numbers of nests in three major colonies and established large areas of mid- to low-density black brant nesting in association with colonies. Byrd and Smith (1981) did not find, however, that nesting was continuous throughout the area first described by Spencer et al. (1951). It is not clear whether the difference between Spencer et al. (1951) and Byrd and Smith (1981) represented a change in abundance and distribution of black brant nesting on the YKD between 1951 and 1981 or differences in perception between the more subjective assessment of Spencer et al. (1951) and the more quantitative estimates of Byrd and Smith (1981). Sedinger et al. (1993) estimated that 82% of YKD black brant nests were in colonies and that nearly all production of young black brant could be accounted for by the major colonies on the YKD in 1992. Stehn et al. (2011) estimated that an average of 64% of YKD black brant nests were in colonies during 1986–1993, a period when colonies were recovering from catastrophic predation events in the early 1980s (Anthony et al. 1991; Sedinger et al. 2016).

Numbers of nests in colonies declined 46% since the last peak in abundance of black brant on the YKD in 1994−1997 (Stehn et al. 2011; Wilson 2018). Declines in numbers of nests in the major colonies on the YKD is of concern because the YKD has long been recognized as supporting most black brant nests (Sedinger et al. 1993; Lewis et al. 2013). In addition, nest success has been thought to be greater inside than outside colonies (Raveling 1979), and growth rates of goslings were greater for goslings associated with one colony (Tutakoke River) than with dispersed nesting areas (Nicolai et al. 2008). Because gosling growth is highly predictive of first-year survival (Sedinger and Chelgren 2007) and future breeding (Sedinger et al. 2004), these differences between colonial and dispersed-nesting black brant predict greater rates of population decline in dispersed-nesting areas than in colonies, unless dispersal from other nesting areas is counterbalancing in situ decline (Dias 1996) or demographic rates for dispersed-nesting black brant now differ from those indicated by earlier studies. Dispersal rates away from natal nesting areas are low, however, suggesting that rescue by immigration may be unlikely (Lindberg et al. 1998; Sedinger et al. 2008).

The U.S. Fish and Wildlife (USFWS) Service initiated a program of searching randomly located plots in the coastal zone of the YKD in 1985 (Saalfeld et al. 2017; Fischer et al. 2018) to locate nests of waterfowl in response to substantial declines in numbers of geese that nest there (King and Derksen 1986). We initially stratified location of plots to maximize precision of estimates of cackling goose Branta hutchinsii abundance, but we changed stratification in 1994 to improve precision of estimates of spectacled eider Somateria fischeri abundance (Saalfeld et al. 2017).

Stehn et al. (2011) estimated modest declines (λ = 0.99) for black brant nesting in geographical strata of varying densities outside of the major colonies between 1993 and 2011 and greater declines (λ = 0.95) in major colonies, resulting in a net decline in nesting black brant on the YKD over this period. The analysis of Stehn et al. (2011) relied on the Yukon Delta Aerial Breeding Waterfowl Survey (Platte and Stehn 2015), corrected using the relationship between numbers of nests (from random plots; Fischer et al. 2018) and black brant counts from aerial survey segments over the same substrata for areas outside the major colonies, and aerial photographs for the colonies themselves (Anthony et al. 1995; Wilson 2018). There were two areas of uncertainty associated with this analysis. First, the generality of the multiplier relating aerial survey data to ground-based densities based on plots across the full range of nesting densities is not well understood. Second, it is not clear that relationships between counts of black brant from aerial surveys and counts of nests from ground plots can be extrapolated to areas lacking nest plots or aerial photographic surveys. Critically, the analysis may not correctly account for shifts in numbers or distribution of non- or failed-breeding black brant that occur in flocks in some areas of the YKD. For example, nonbreeding black brant may be counted as breeding pairs by aerial observers.

Saalfeld et al. (2017) analyzed spatial-temporal dynamics of greater white-fronted geese Anser albifrons frontalis, cackling geese, emperor geese Anser canagicus, and spectacled eiders in addition to black brant nesting on the YKD over the period 1985–2013 by using data generated by the USFWS random plot program (Fischer et al. 2018). They relied on random forest models (Breiman 2001) that incorporated environmental variables in addition to temporal trends. Saalfeld et al. (2017) reported a slight decline in numbers of black brant nesting predominantly, but not entirely, outside of colonies, although they did not provide estimates for the precision of their abundance estimates. It should also be noted that the principal goal of Saalfeld et al. (2017) was understanding spatial variation and habitat associations of study species, rather than understanding trend. Dynamics of the species included in Saalfeld et al. (2017) all changed abruptly in the mid-1990s, coinciding with the shift in sampled strata, initiated to improve estimates of numbers of spectacled eiders.

We analyzed data generated by the Yukon Delta Nesting Waterfowl Survey (Fischer and Stehn 2014; Fischer et al. 2018) to estimate the numbers of black brant nests in sampled areas between 1986 and 2016. Our goal was to assess temporal patterns in black brant outside of the major colonies on the YKD without the necessity of assumptions required by the use of aerial survey data or the inclusion of plots located within colonies (Saalfeld et al. 2017).

Methods

Each year, two to four individuals searched a sample of randomly located rectangular plots in the central coastal zone of the YKD in an attempt to locate all successful and unsuccessful nests of all waterfowl species (Saalfeld et al. 2017; Fischer et al. 2018). We selected plots from 33 substrata and mapped on Ikonos satellite imagery to aid investigators in locating plots and their boundaries (Table 1; Table S1, Supplemental Material). For our analysis, we used boundaries developed by Stehn et al. (2011) to poststratify plots into five larger strata based on nest density, proximity to black brant colonies, and proximity to the coast. Stehn et al. (2011) labeled these strata periphery, coastal, transition, inland, and upland. The upland stratum contained no black brant nests, so we did not consider it further. Both transition and inland strata supported low densities of black brant nests, and we pooled them for the analyses herein. This left us with three larger strata: peripheral, coastal, and inland (Figure 1). We sampled a subset of the total study area only during 1986–1999 (Table S1); we refer to strata in this area as the historical strata (Figure 1). We sampled 18 substrata representing 36% of the sampled area over the period 1986–2016 (Figure 1), although in this subset, we did not sample substrata associated with the peripheral stratum in 1986. We refer to these strata as the long-term strata. Thus, we defined six strata representing the combination of three density/geographical classes (peripheral, coastal, and inland) and two sampling durations (historical and long-term). Substrata ranged in size from 10.7 to 459.9 km2 during the historical period and from 9.9 to 89 km2 in the long-term data. Rectangular plots were 0.32 km2 in all years except 1995 and 1996, when plots were square and 0.45 or 0.36 km2. We excluded plots ≥0.36 km2 to reduce variance associated with plot size. Data are available in Table S2 (Supplemental Material).

We analyzed number of nests per plot for both the long-term and historical data using a negative binomial regression in a Bayesian framework. We fit the temporal process for the mean of the negative binomial as a log-linear function of year. We allowed for different intercepts for each of the six strata. We fit single linear and quadratic regression coefficients for each stratum type (e.g., historical and long-term peripheral strata). That is, we used data from both the historical and long-term strata to fit a single temporal trend for each density class, while allowing for the potential of different mean densities between the historically and long-term sampled areas as reflected in different intercepts. We included quadratic terms for year in candidate models to allow for nonlinearities in trend through time. We used a vague normal prior, N(0,100), for the log of the stratum-specific negative binomial size parameter (ri) and moment matching (Hobbs and Hooten 2015) to link estimates of the mean and ri to produce estimates of the negative binomial probability parameter (pi). We used vague normal priors, N(0,100), for the parameters in the log-linear functions of the mean. We initially attempted to use a zero inflated regression approach (Kéry and Schaub 2012), also with a temporal trend (modeled with a logit link) on the slope and intercept of the probabilities that plots contained at least one black brant nest (occupancy, modeled using Bernoulli trials). Chains representing the slope and intercept for the trend in the occupancy parameters failed to converge, even after 500,000 iterations. This was also true for zero-inflation models that included only an intercept term for the probability of occupancy. Consequently, we removed zero-inflation from subsequent analyses. We used Markov Chain Monte Carlo (MCMC) to produce posterior distributions of parameter estimates. We ran three chains with 100,000 iterations and a burn-in period of 50,000 iterations; we retained every fifth iteration. We used the Gelman–Rubin diagnostic (R-hat) and visual inspection to assess convergence of MCMC chains.

We estimated numbers of nests per stratum (e.g., peripheral long-term) by multiplying number of nests per plot by the ratio of stratum area to plot area. We estimated posterior distributions for the predicted numbers of nests as the product of the estimated mean of the negative binomial and the ratio of stratum size to plot size for each plot. We estimated the number of nests in each stratum (e.g., peripheral) as the sum of the estimated mean number of nests in the historical and long-term strata of that type in each year from the regressions described earlier. Similarly, we estimated the total number of dispersed nests as the sum of the estimated mean number of nests across the six strata in each year.

We estimated the change in total dispersed nests over the entire study period (1986−2016), for the period between 1993 and 2016, which represented the middle of the 3-y periods centered on the first and last years of video surveys of colonies available to us (Wilson 2018), and for the last decade of the study by subtracting number of nests in 1986, 1993 and 2007 from the number in 2016. We estimated the proportion of black brant nests that occurred in colonies by dividing estimates of numbers of black brant nests in colonies from Wilson (2018) by the sum of estimated numbers of dispersed nests from analyses in this paper and estimates of numbers of colony nests. We assumed estimates of colony nests were normally distributed. We used annual estimates and associated standard errors of colony estimates from Wilson (2018) to parameterize a normal distribution from which we drew a sample in each iteration of the MCMC chain. We estimated the proportion of black brant nests in colonies and 95% credible intervals (CIs) from the median and 2.5 and 97.5% quantiles of the proportion from the MCMC chains. We report medians and 95% CIs for parameter estimates and estimates of numbers of nests. R code for analyses is provided in Table S3 (Supplemental Material).

Results

The historical data set included 63, 43, and 241 plots from peripheral, coastal, and inland strata, respectively (Table 1). Number of plots in each year-substratum combination are in Table S1. Plots from the peripheral stratum from this period were exclusively associated with the Kokechik Bay colony, and areas north or west of the Kashunuk River were sampled only during this period (Figure 1). Most plots contained no black brant nests (30 of 63 from the peripheral stratum, 31 of 43 from the coastal stratum, and 220 of 226 plots from the inland stratum).

The long-term data set included 205, 566, and 945 plots from the peripheral, coastal, and inland strata (Figure 1; Table 1), of which 145, 252, and 155 plots, respectively, contained at least one black brant nest. All MCMC chains converged (R-hat ≤ 1.01) Credible intervals for both linear and quadratic trends in nests per plot substantially overlapped zero for the peripheral and coastal strata, whereas the linear and quadratic terms for the inland stratum were positive and negative, respectively (β = 0.009, 95% CI: −0.117 to 0.126; β = 0.075, 95% CI: −0.030 to 0.179; β = 0.196, 95% CI: 0.065−0.322 for peripheral, coastal, and inland strata, respectively, linear terms and β = −0.0002, 95% CI: −0.0038 to 0.0035; β = −0.0014, 95% CI: −0.0042 to 0.0015; β = −0.0042, 95% CI: −0.0076 to −0.0006 for peripheral, coastal, and inland strata, respectively, quadratic terms), indicating weak or nonexistent trends in numbers of nests in all three strata (Figure 2). We estimated 4,097 (95% CI: 2,262−8,331), 2,151 (95% CI: 1,115−4,483), 147 (95% CI: 62−357), and 6,584 (95% CI: 4,221−11,269) nests in the peripheral, coastal, inland strata, and overall, respectively, in 1986 (Figure 2). We estimated these strata contained 4,437 (95% CI: 2,180−9,392), 5,460 (95% CI: 3,597−7,870), 917 (95% CI: 498−1,798), and 11,050 (95% CI: 7,500−17,460) nests in 2016 (Figure 2). We estimated a median increase of 4,419 (95%CI: −883 to 10,636) in dispersed nests from 1986 to 2016 (Figure 3). Median estimate of increase in nests from 1993 through 2016 was 2,916 (95%CI: −1,493 to 9,623), whereas median number of dispersed nests was stable over the last decade of the study (median change −69 nests, 95% CI: −4,009 to 5,589) (Figure 3). Proportion of black brant nests in colonies declined from 0.71 (95% CI: 0.66−0.75) in 1992–1994 to 0.51 (95% CI: 0.40−0.61) in 2016 (Figure 4).

Discussion

Contributions of dispersed-nesting black brant to the YKD nesting population

Our results, in conjunction with other work (Stehn et al. 2011; Saalfeld et al. 2017), indicate that there is substantial uncertainty regarding the number of black brant breeding outside of colonies on the YKD. Nevertheless, the analyses we present here provide guidance about the likely range of contributions by dispersed-nesting black brant to the YKD nesting population. We estimated a median of 6,584 nests occurred outside of major colonies on the YKD in 1986 and an average of 8,171 such nests existed during 1992–94, the first 3 y of video surveys of the colonies (Anthony et al. 1995). Video surveys estimated an average of 19,969 nests in the colonies on the YKD in 1992–1994 (Wilson 2018). We estimated that dispersed nests represented about 29% of black brant nests on the YKD when video surveys began. We note that three colonies sampled using ground plots in 1981 and 1982 contained 46% more nests than in 1992 (Sedinger et al. 1993; Wilson 2018). Spencer (1951) described a continuous distribution of black brant nesting in coastal habitats, in what we classify as coastal strata, in numbers that were “almost uncountable,” whereas we found that only 43% of plots in coastal strata contained a black brant nest. Thus, abundance of nesting black brant on the YKD in the early years of this study may have been lower than that before 1980.

We estimated a median increase of 2,916 nests outside of colonies from 1993 through 2016. Video surveys of the major colonies indicate declines of 10,270 nests between 1993 and 2016 based on the 3-y averages centered on those years (Wilson 2018). Thus, under the most likely scenario resulting from our analyses, increases of black brant nests in dispersed-nesting areas compensated for approximately 28% of declines in the major colonies. Declines in nests on colonies have increased the relative importance of dispersed-nesting black brant, which we estimated represented 49% of YKD black brant nests in 2016. It is important to recognize that we detected no increase in dispersed-nesting black brant over the last decade of this study, a period during which colonies declined by 4,956 nests.

Uncertainties in trend in dispersed-nesting black brant

There are three important contributors to uncertainty about trend in numbers of nesting black brant outside of major colonies on the YKD. First, there was virtually no overlap in substrata sampled during the historical and long-term periods; in fact, substrata from the peripheral and coastal strata were essentially spatially disjoint between the two periods. For example, substrata comprising the peripheral stratum were adjacent to the Kokechik Bay colony during the historical period, whereas these substrata were adjacent to the Tutakoke and Kigigak colonies in the long-term data. The disjoint nature of substrata between the area sampled only during the first 13 y of this study and the long-term sample creates potential confounding between spatial and temporal variation. We do not believe it is possible to fully reconcile this problem with existing data. In addition, although we estimated trend in each stratum type (e.g., peripheral) using data combined from the historically and long-term sampled areas, trend (and precision of the trend) over the past 22 y of the study was dominated by the long-term strata.

Second, credible intervals for regression coefficients of trends in numbers of nests in long-term strata indicated weak evidence for increases in dispersed-nesting black brant and substantial uncertainty in numbers of dispersed nests during any given year (Figures 2 and 3). We justify our decision to use “nonsignificant” parameter estimates to assess temporal trends as follows. Uncertainty in temporal trends was fully reflected in credible intervals for predicted numbers of nests in each stratum-year combination, although precision of our estimates for the historical strata is contingent on the assumption that trends were similar between the historical and long-term strata over the past 22 y of the study. Nevertheless, patterns in the data that do exist indicate that it is unlikely that increases in dispersed-nesting black brant have been sufficient to offset declines in the major colonies on the YKD.

And third, our results differ from those of Saalfeld et al. (2017) who reported slightly declining densities of nests based on a largely similar data set. Saalfeld et al. (2017) accounted for habitat characteristics, whereas we did not. In contrast, our separation of the data into historical vs. long-term data sets, partially addressed change in sampled area in the mid-1990s, whereas Saalfeld et al. (2017) did not. A small proportion (3%) of the plots analyzed by Saalfeld et al. (2017) were placed in colonies (which we excluded); inclusion of these plots could have influenced the ability of Saalfeld et al. (2071) to detect a trend. The trend in these plots from colonies was not significant between 1993 and 2016, however, and should not have substantially impacted the overall trend they report. For now, however, the contrasting patterns in our study and Saalfeld et al. (2017) suggest caution in interpreting trend in dispersed-nesting black brant on the YKD.

Why are trajectories different for colonial vs. dispersed-nesting black brant?

Although considerable uncertainty exists about trends in numbers of dispersed- nesting black brant on the YKD, our analyses suggest they are either stable or slightly increased, at least until 2007, in contrast to substantial declines in colonial nesting black brant. This result seems surprising, given historically lower nest survival (Raveling 1979) and lower growth rates of goslings originating from dispersed-nesting areas (Nicolai et al. 2008). It is unlikely that differential adult or juvenile survival explains the difference in trajectories between the two groups because declines in adult survival are widespread (Leach et al. 2017) and lower growth rates for goslings from dispersed nests (Nicolai et al. 2008) should reduce their first-year survival below that of goslings originating from colonies (Sedinger and Chelgren 2007; Leach et al. 2017). Dispersal between colonies, or from colonies to dispersed-nesting areas, does not appear sufficient to account for differential dynamics of dispersed- vs. colonial-nesting black brant (Lindberg et al. 1998; Nicolai et al. 2008; Sedinger et al. 2008; Fondell, unpublished data).

One hypothesis is that historical differences in nest success no longer occur. Black brant nesting at Tutakoke River have experienced increased frequency of high rates of nest failure caused by arctic foxes Vulpes lagopus since the early 1980s (Anthony et al. 1991; Sedinger et al. 2016). Patterns in both fall age ratio data and photo surveys of other colonies, however, indicate that high rates of nest failures are widespread (Ward et al. 2018; Wilson 2018). It is, nevertheless, possible that these frequent fox predation events have been more concentrated on colonial nesting black brant such that nest success has been on average higher outside of colonies in recent decades, which has partially buffered dispersed-nesting black brant from the declines apparent in colonies.

Recommendations for the future

We have three principal recommendations. First, we believe nest counts provide a more direct measure of size of breeding populations of black brant than aerial counts corrected by ground and photographic surveys; thus, nest counts should be used as the primary method to inform management decisions for black brant on the YKD until additional assessment has been completed. Second, we recommend expanding the area sampled to re-establish some sampling in the historical strata. This change would establish sampling throughout most of the area on the YKD where black brant nest. Third, we believe it is important to enhance our understanding of the dynamics of black brant nesting outside major colonies. We suggest increased effort to understand nest success and other demographic rates for dispersed-nesting black brant.

Supplemental Material

Please note: The Journal of Fish and Wildlife Management is not responsible for the content or functionality of any supplemental material. Queries should be directed to the corresponding author for the article.

Table S1. Numbers of plots sampled for black brant Branta bernicla nigricans in each substratum and year combination in both historical (sampled only in 1986–1999) and long-term strata (sampled 1986–2016) on the Yukon-Kuskokwim Delta, Alaska. Substratum numbers follow those in Stehn et al. (2011).

Found at DOI: https://doi.org/10.3996/052019-JFWM-037.S1 (20 KB DOCX).

Table S2. Data used to analyze trends in numbers of black brant Branta bernicla nigricans nests outside of major colonies on the Yukon-Kuskokwim Delta, Alaska. Columns are year, BrantNests (number of nests on a plot), plot_area (area of plot in square meters), AGCV_AREA (area of substratum in square meters), AGCV_STRAT (substratum number, used to assign substrata to strata), E2 (indicator assigning plots to sampling area for long-term strata), random (whether a plot was randomly located or not), noncolony (whether a plot was outside one of the major colonies), Stehn_Sedge_stratum (numbers used in jags code to assign plots to long-term or historical peripheral, coastal, or inland strata), Str_area (area of strata in square meters), and occ (whether a plot contained at least one black brant nest or not). We excluded samples for which the noncolony and random variables were zero and samples from long-term strata (Stehn_Sedge_stratum = 2,4,6) for which E2 = 0. We also excluded samples for which plot size was >0.34 km2.

Found at DOI: https://doi.org/10.3996/052019-JFWM-037.S2 (347 KB CSV).

Table S3. R code to handle data, perform analyses and construct graphs for black brant Branta bernicla nigricans nesting outside colonies on the Yukon-Kuskokwim Delta, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037S3 (18 KB DOCX).

Reference S1. Byrd GV, Finger S, Janik CA, Joseph M, Paniyak P. 1982. The status of geese and swans nesting on the coastal fringe of the Yukon Delta National Wildlife Refuge. Unpublished report, Yukon Delta National Wildlife Refuge, U.S. Fish and Wildlife Service, Bethel, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037.S4 (2.27 MB PDF).

Reference S2. Byrd GV, Smith MF. 1981. A summary of data from 160-acre random plots surveyed on the Yukon Delta National Wildlife Refuge in 1981. Unpublished report, Yukon Delta National Wildlife Refuge, U.S. Fish and Wildlife Service, Bethel, Alaska.

Found at DOI: https://doi.org/10.3996/052019-JFWM-037.S5 (1.11 MB PDF).

Reference S3. Dufresne F. 1924. Report on investigations of wildfowl of the Hooper Bay section of Alaska during the spring and summer of 1924. Unpublished report, Biological Survey, U.S. Fish and Wildlife Service, Anchorage, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037.S6 (3.33 MB PDF).

Reference S4. Fischer JB, Stehn RA. 2014. Nest population size and potential production of geese and spectacled eiders on the Yukon-Kuskokwim Delta, Alaska, 1985–2014. Unpublished report, Migratory Bird Management, U.S. Fish and Wildlife Service, Anchorage, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037.S7 (762 KB PDF).

Reference S5. Olson SG. 1951. A study of goose and brant nesting on the Yukon-Kuskowkim Delta. Unpublished report, U.S. Fish and Wildlife Service, Alaska Game Commission Federal Aid Wildlife Restoration Quarterly Report.

Found at DOI: https://doi.org/10.3996/052019-JFWM-037.S8 (5.73 MB PDF); also available at https://ecos.fws.gov/ServCat/DownloadFile/50450?Reference=50036.

Reference S6. Platte RM, Stehn RA. 2015. Abundance and trend of waterbirds on Alaska's Yukon-Kuskokwim Delta coast based on 1988 to 2014 aerial surveys. Unpublished report, U.S. Fish and Wildlife Service, Anchorage, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037.S9 (1.3 MB PDF).

Reference S7. Stehn RA, Platte RM, Wilson HM, Fischer JB. 2011. Monitoring the nesting population of Pacific black brant. Unpublished report, Migratory Bird Management, U.S. Fish and Wildlife Service, Anchorage, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037.S10 (511 KB PDF).

Reference S8. Wilson HM. 2018. Aerial photographic survey of brant colonies on the Yukon-Kuskokwim Delta, Alaska, 2017. Unpublished report, Migratory Bird Management, U.S. Fish and Wildlife Service, Anchorage, Alaska.

Found at DOI: http://doi.org/10.3996/052019-JFWM-037.S11 (485 KB PDF).

Acknowledgments

We thank Michael Swaim for providing random plot data for brant and the hundreds of staff and volunteers that have participated in the Nesting Waterfowl Survey. We thank Jason Schamber for providing some of the unpublished federal government reports included in Supplementary Material. We also thank Courtney Amundson, an Associate Editor, and an anonymous reviewer for helpful comments on an earlier draft of this manuscript.

Any use of trade, product, website, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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Author notes

Citation: Sedinger JS, Riecke TV, Street PA, Fischer JB. 2020. Dynamics of dispersed-nesting black brant on the Yukon-Kuskokwim Delta. Journal of Fish and Wildlife Management 11(1):112–120; e1944-687X. https://doi.org/10.3996/10.3996/052019-JFWM-037

Competing Interests

The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service.