Temporal Trends in Body Condition of Arctic Geese Wintering in the Mississippi Alluvial Valley

Midcontinent populations of arctic nesting geese (hereafter, arctic geese), including greater white-fronted geese Anser albifrons frontalis, lesser snow geese Anser caerulescens caerulescens, and Ross's geese Anser rossii, have increased in abundance and shifted their winter distribution in recent decades. Consequently, the number of arctic geese wintering in the Mississippi Alluvial Valley (MAV) has increased since the 1980s. Stored endogenous nutrients are critically important to the life cycle of arctic geese as the geese use these stored nutrients to complete long-distance migration events, survive harsh winters, and supplement nutrients needed for reproduction. This study tracked temporal changes in body condition of arctic geese during the wintering period. We collected arctic geese from October–February 2015–2016 and 2016–2017 in eastern Arkansas. We used proximate analysis to determine size of lipid and protein stores as an index of body condition. Protein stores were more stable through time than lipids, but we observed a slight increase in all species as winter progressed. Mean lipid stores were dynamic and were highest in November and lowest in February. Greater white-fronted geese arrived earliest to the MAV and experienced an increase in endogenous lipid stores during early winter when high-energy food resources were most abundant. Conversely, snow and Ross's geese arrived to the MAV later and did not appear to increase their lipid stores upon arrival. All three species experienced a decline in stored lipid mass as winter progressed; a combination of factors such as resource depletion, a shift in dietary needs, physiological factors, hunting pressure, and increased energetic demands may have driven the decline. An improved understanding of the role that “nontraditional” wintering grounds exert on the nutrient dynamics of arctic geese may aid in the management of growing and shifting populations.

Fitness heterogeneity in adult Snow and Ross’s geese: Survival is higher in females with brood patches

Life-history theory broadly predicts a fitness tradeoff between costs of raising offspring and parental survival. Waterfowl with precocial young face particularly high costs of egg production, incubation, and brood-rearing, but not all evidence supports a corresponding decline in survival. We used multi-state mark–recapture–recovery models to estimate annual probabilities of survival, reported mortality, and transition between 2 states for female Ross’s Geese (Anser rossii) and Lesser Snow Geese (A. caerulescens caerulescens) that attempted nesting near Karrak Lake, Nunavut, Canada. States were possession of a brood patch (high likelihood of successful nesting, “B”) vs. no brood patch (attempted nesting but failed, “N”). Based on over 43,000 birds marked from 2000 to 2015, we found that females of each species with a brood patch had consistently higher probabilities of survival than those without, subsequent to capture in early August. Virtually all of the state differences in survival were due to nonhunting mortality. These patterns are consistent with the concept of variable individual quality impacting vital rates across multiple seasons. Higher survival of females with brood patches may be linked to greater breeding success but also to a hypothesized dominance advantage afforded to family groups of geese during winter. Moreover, although hunting pressure can play a key role in regulating Arctic goose populations, it does not appear to affect this relationship between inferred breeding state and survival. Instead, coincident with recent declines in harvest rate in these populations, higher individual quality of breeding females appears to outweigh the higher hunting vulnerability of presumed parents with young. The potential influence of social dominance in reducing natural winter mortality among families may thus contribute to the survival advantage seen in successful, relative to failed, breeders.

Heterogeneity in body condition, survival, and seasonal origins among lesser snow and Ross's geese

Individual heterogeneity in fitness within a population is well established and provides the required variability for natural selection to take place. Yet, in the case of overabundant midcontinent lesser snow (Anser caerulescens caerulescens) and Ross's geese (A. rossii), individual variation in regards to harvest effects on population growth has largely not been considered when evaluating management actions to reduce population size. In this dissertation, I first examined heterogeneity in body condition among hunter harvested individuals and the general population of midcontinent lesser snow and Ross's geese during the spring Light Goose Conservation Order in 2015 and 2016 across Arkansas, Missouri, Nebraska, and South Dakota. I found a body condition bias in decoy harvested geese, such that individuals removed by hunters were in lower body condition (less lipid content) relative to the general population. This finding suggests that disproportionate removal of lower conditioned individuals is a feature of the currently observed compensatory nature of harvest among midcontinent light geese. I also explored methods to estimate the magnitude of individual variation in survival rates of adult lesser snow geese using mark-recovery data via a Bayesian state-space model. I identified limitations to estimating heterogeneous survival rates using mark-recovery data alone and suggest future simulations to explore alternative methodological approaches. Finally, I evaluated differences in spring body condition among individuals using different wintering habitats through stable isotope analysis. I found that individuals overwintering in coastal marsh habitats had lower lipid reserves relative to those individuals overwintering in rice-based agricultural landscapes, suggesting a carry-over effect from winter habitat use that may influence harvest susceptibility or other fitness parameters. In conclusion, continued research to identify the amount of individual variation in survival parameters of cohort specific geese can further elucidate the role of heterogeneity on the Light Goose Conservation Order attempts to reduce population size.

Ross’s Goose (Chen rossi) Nesting Colony at East Bay, Southampton Island, Nunavut

Most Ross’s Geese (Chen rossi) nest in the central arctic of North America, but the range has expanded eastward in the last two decades. In summer 2014, we discovered a cluster of 48 nesting pairs of Ross’s Geese at East Bay Migratory Bird Sanctuary,Southampton Island, Nunavut. The Ross’s Goose colony was between an upland Lesser Snow Goose (Chen caerulescens caerulescens) nesting area and a low-lying Cackling Goose (Branta hutchinsii) and Atlantic Brant (Branta bernicla) nesting area, in a zone dominated by ponds and lakes and interspersed with areas of moss and graminoids. Our discovery documents a previously unknown level of nesting of Ross’s Geese at East Bay and corroborates unpublished evidence of growing numbers of the species on Southampton Island and expansion of its breeding range.

Evidence for Toxoplasma gondii in migratory vs. nonmigratory herbivores in a terrestrial arctic ecosystem

It is currently unclear how Toxoplasma gondii (Nicolle and Manceaux, 1908) persists in arctic tundra ecosystems in the absence of felid definitive hosts. To investigate potential transmission routes of T. gondii in a terrestrial arctic food web, we collected samples from two migratory herbivores, Ross’s Geese (Chen rossi (Cassin, 1861)) and Lesser Snow Geese (Chen caerulescens (L., 1758)), and from two resident herbivores, Nearctic brown lemmings (Lemmus trimucronatus (Richardson, 1825)) and collared lemmings (Dicrostonyx groenlandicus (Traill, 1823)), trapped at Karrak Lake, Nunavut, Canada. Antibodies were detected in 76 of 234 (32.4%) serum samples from Ross’s Geese and 66 of 233 (28.3%) serum samples from Lesser Snow Geese. We did not detect T. gondii antibodies in filter-paper eluate tested from thoracic fluid samples collected from 84 lemmings. We did not detect T. gondii DNA in brain tissue from these lemmings. Although a small sample size, our findings suggest that lemmings in this terrestrial arctic ecosystem are not exposed to, or infected with, the parasite. This suggests that oocysts are not introduced into the terrestrial arctic ecosystem at Karrak Lake via freshwater runoff from temperate regions. This study demonstrated that live adult arctic-nesting geese are exposed to T. gondii and therefore migratory herbivorous hosts are potential sources of T. gondii infection for predators in terrestrial arctic ecosystems.