Journal
JOURNAL OF WILDLIFE MANAGEMENT
Volume 81, Issue 7, Pages 1210-1218Publisher
WILEY
DOI: 10.1002/jwmg.21284
Keywords
band recovery rates; Branta bernicla nigricans; Brownie models; joint live and dead mark-recapture; population dynamics; Seber reporting rate
Funding
- U.S. Geological Survey, Alaska Science Center
- U.S. Fish and Wildlife Service, Migratory Bird Management Region 7
- Ducks Unlimited de Mexico
- Ducks Unlimited
- Arctic Goose Joint Venture
- North American Wetland Conservation Fund
- Environment and Climate Change Canada
- Nature Trust of British Columbia
- Morro Bay Brant Group
- National Science Foundation [OPP 9214970, DEB9815383, OPP9985931, OPP0196406, DEB 0743152, DEB 1252656]
- Conoco-Phillips Alaska
- Great Basin Cooperative Extension Unit (CESU) [G11AC20324]
- U.S. Geological Survey, Alaska Science Center [G11AC20324]
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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. (c) 2017 The Wildlife Society. We found that survival of gosling and adult black brant from subarctic and arctic breeding areas in Alaska and western Arctic Canada has declined since 1990. Numbers of brant nests on major colonies, fall age-ratios, and survival rates have all declined; however, estimates of abundance from mid-winter surveys have increased in recent years, indicating further work is needed to resolve conflicting abundance and demographic data for brant.
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