USGS Science⌕ Search
Home/Archive/USGS

USGS · 70196241

Declining survival of black brant from subarctic and arctic breeding areas

Alan G. Leach·David H. Ward·James S. Sedinger·Mark S. Lindberg·W. Sean Boyd·Jerry W. Hupp·Robert J. Ritchie
View original source ↗Export metadata ↓

Abstract

Since the mid 1990s, the number of black brant ( Branta bernicla nigricans ; brant) nests on the Yukon‐Kuskokwim Delta (YKD), Alaska, USA, the historically predominant breeding area of brant, has declined steadily. This has caused researchers and managers to question if arctic breeding populations can compensate for the reduction in brant nests on the YKD. An important component of the assessment of brant population dynamics is having current estimates of first‐year and adult survival. We banded brant at 4 locations in Arctic Alaska and western Canada, and at 1 location in the subarctic, the Tutakoke River (TR) colony on the YKD, 1990–2015. We used joint live and dead mark‐recapture models to estimate first‐year and adult (≥1 yr old) survival of brant. We also used band recovery rates from a Brownie model to assess temporal trends in band recovery rates of adult brant. First‐year survival of brant hatched at TR declined from approximately 0.60 to <0.20 and, although first‐year survival generally was higher for goslings marked in the Arctic, their survival declined from approximately 0.70 in the early 1990s to ≤0.45 in the 2010s. Annual survival of adult females decreased from an average of 0.881 (95% CI = 0.877–0.885) to 0.822 (95% CI = 0.815–0.829) at TR and from 0.851 (95% CI = 0.843–0.860) to 0.821 (95% CI = 0.805–0.836) in the Arctic, from 1990 to 2014. Band recovery rates of adults generally were <1.25% until the last several years of study, when they reached ≤3.5%. Although the current harvest rates may be partially additive to natural mortality, we do not believe that harvest is the main influence on the declines in survival. The general decline in survival rates of brant breeding across a large geographic area may be influenced by a reduction in the quality of migration and wintering ground habitats. We suggest an analysis of seasonal survival of brant to test the hypothesis that declining habitat quality on wintering or spring migration areas is reducing survival. Our results suggest that the number of breeding pairs at TR will continue to decline and also brings into question the ability of arctic breeding populations to grow at a rate necessary to offset the declines on the YKD. Researchers should continue to closely monitor survival and harvest rates of brant, and assess methods currently used to monitor their abundance.

Explore related subjects

Journal of Wildlife ManagementArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Alan G. Leach, David H. Ward, James S. Sedinger, Mark S. Lindberg, W. Sean Boyd, Jerry W. Hupp, Robert J. Ritchie. 2017-06-15. Declining survival of black brant from subarctic and arctic breeding areas. https://doi.org/10.1002/jwmg.21284

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Duck nesting response to experimental management of upland habitats in California

Habitat loss and limited upland nesting cover likely constrain waterfowl productivity in intensively managed wetland landscapes in California, USA. We evaluated whether experimental manipulations of upland habitats, including the seeding of native plants, dense nesting cover, or cereal grains, could enhance nesting vegetation and improve duck nest density and nest survival in a Mediterranean climate. During 2008 to 2013, we used a before-after-control-impact (BACI) experimental design within 15 upland grassland fields (each 12–28 ha in size) at a state wildlife area to evaluate habitat management treatment effects on nest site vegetation, vegetation structure, and reproductive performance of mallard ( Anas platyrhynchos ) and gadwall ( Mareca strepera ). The BACI design allowed vegetation and duck nesting responses in treated fields to be compared to untreated control fields both before and after treatment implementation. Prior to treatment implementation, all study fields consisted of upland grasslands dominated primarily by non-native annual grasses typical of Mediterranean-climate ecosystems in California. Relative to control fields, we observed only limited improvement to duck nest success in fields seeded with cereal grains and dense nesting cover, whereas fields seeded with native plants showed persistently lower duck nest survival. Vegetation composition after treatment application shifted rapidly from plants that were purposefully seeded to non-native grasses (e.g., Italian ryegrass [ Lolium multiflorum ]) by the second and third years after treatment. Vegetation structural metrics (i.e., visual obstruction height, lateral density, and canopy density) also showed limited or no improvement attributable to the experimental treatments. Across nearly all treatment and control fields, duck nest densities increased during the first several years following treatment implementation but later declined towards pre-treatment levels by the fourth year after treatment. However, mallard nest densities increased much more markedly in native fields than in control fields in the early post-treatment years but declined again in later post-treatment years, suggesting limited long-term benefit. Clutch size, nest initiation date, and egg hatching success were not affected by treatments. Our results indicate that vegetation management and direct seeding had limited short-term and no measurable long-term benefits to the vegetation's structure, duck nesting densities, or duck nest survival, and upland habitat conditions showed little sustained improvement during later breeding seasons (years 2–4 post-treatment). Upland restoration efforts in agricultural landscapes may need more continued, multi-year habitat management to improve nesting conditions for waterfowl over the long-term.

California↗
USGS2026

Beginning with a single step: A social theory of change for managing chronic wasting disease

Emerging wildlife diseases, like chronic wasting disease (CWD), not only lead to changing dynamics within the ecology of the susceptible species but also to changes within interrelated social and management systems. Chronic wasting disease has proven challenging to manage partially because the best management practices (BMP) available have conflicted with historical cervid management paradigms. In support of CWD management decisions, we conducted an expert elicitation investigation of potential intervention strategies that experts believed would positively affect CWD management. The most prioritized intervention was “understanding audiences, outreach, and engagement with public.” Using the most prioritized intervention theme, we continued the expert elicitation process to develop a social theory of change that describes the expected results of implementing the intervention theme. The results chain describes a process of conducting social science investigation to gather evidence and understand the situation and use the gathered evidence to support the selection of appropriate behavior change strategies and pathways prior to implementing a desired CWD management action. The produced social theory of change provides CWD managing organizations with a framework for evaluating efforts to engage with the public about the actions they are taking and working to increase support or participation.

Journal of Wildlife Management↗
USGS2026

White light reduces flight height of birds in low-density migration corridor

Artificial light at night (ALAN) has been shown to influence the behavior of migratory birds, yet how different light spectra modulate these effects remains unclear. We conducted a field experiment for 31 nights at a remote site in northern Colorado, USA, using 2 800-W light-emitting diode (LED) floodlights with white, red, amber, and blue lighting treatments during fall migration in 2023 and 2024. Using a vertical-looking radar system, we quantified avian in-flight responses in migration traffic rate, flight height, and flight direction between paired control periods with no light and periods with lighting treatments. Although we found no effects of our treatments on migration traffic rate and weak effects on flight direction, we found that broad-spectrum white light with emissions across a 400–600 nm spectrum reduced mean avian flight height by an estimated 22.57 m (±10.53 SE) compared to dark periods, and this response was stronger than red and blue lighting treatments. Our ability to detect behavior changes from a point source in a rural, low-density migration system supports the notion that the effects of artificial light at night on bird behavior may be more pervasive than is often recognized, and that this varies by ALAN spectra. Beyond providing insight into avian orientation and in-flight behavior, our results have implications for future research, the conservation management of artificial light at night, and lighting designs that minimize effects on migratory birds.

Colorado↗