Foraging preferences of Canada geese among turfgrasses: Implications for reducing human–goose conflicts

Canada geese (Branta canadensis) can cause serious damage to turfgrass areas and create human health and safety concerns (e.g., collisions with aircraft, disease transmission). We conducted a study during 2005–2007 to determine if Canada geese exhibit a feeding preference among various commercially available turfgrasses. Behavioral responses of captive geese to 9 turfgrasses, bare ground, and litter were observed over 6 4-week trials during July–September following the installation of selected turfgrasses into experimental arenas. Captive geese preferred to forage on Kentucky bluegrass, creeping bentgrass, and fine fescue sods compared to centipedegrass, St. Augustinegrass, and zoysiagrass. Forage qualities and macronutrient levels varied among the turfgrasses and might explain the foraging preferences geese exhibited during this study. Canada goose feeding rate was positively correlated with crude protein, nitrogen content, and calcium, but negatively correlated with acid detergent fiber content, within various turfgrasses. Our findings suggest careful selection of turfgrasses could be an effective method for reducing Canada goose conflicts in urban and suburban areas. © 2011 The Wildlife Society.     

Spring staging in Brent Geese Branta bernicla: feeding constraints and the impact of diet on the accumulation of body reserves

Summary The diet composition of Brent Geese Branta bernicla on a salt-marsh was quantified. Puccinellia maritima was the principal food species, while Plantago maritima and Triglochin maritima were less commonly taken. Festuca rubra only acted as a substitute for Puccinellia when production of the latter species dropped. The metabolizable energy of the food plants ranged from 5 to 11 kJ·g^–1. By assessing the ingestion rates of geese feeding on different food species, the net intake rate could be derived. Plantago and Triglochin appeared to be the most profitable plants to eat. The proportion of these species in the diet was restricted by (1) the capacity of the alimentary tract, since high intake rates combined with high water contents of the food plants easily led to overfill; and (2) the limited distribution of these plants, in combination with their rapid depletion by grazing geese. These latter factors led to an unequal allocation among individual geese. Most Plantago and Triglochin was obtained by dominant pairs within the flocks. The high quality of Puccinellia allowed geese to gain mass in spring, but the metabolizable energy of this plant species declined during the staging period, and Plantago and Triglochin increased in importance in supplying the geese with components with which to build their body reserves. The timing of the onset of spring growth of the various food species differed between years, and plant phenology was shown to have a profound effect on the final body reserves of the geese.     

An approach to the assessment of change in the numbers of Canada Geese Branta canadensis and Greylag Geese Anser anser in southern Britain

Capsule Population change in geese was assessed using an approach that requires a relatively small sampling effort.

Aims During the 1999 breeding season a survey was carried out to determine if the numbers of introduced Canada and re-established Greylag Geese in southern Britain had changed since 1988–91 and whether any change had occurred in areas with previously high or low Canada Goose densities.

Methods A randomized stratified sample of 246 tetrads from the 24 156 tetrads covered between 1988–91 in this area, as part of the New Atlas of Breeding Birds, were resurveyed. Eight habitat categories were used in the stratification and were based on 1-km-square summary data obtained from the CEH Land Cover Map of Great Britain (water cover and urbanization) and LANDCLASS stratification (upland/lowland). The five habitat categories with the highest densities of Canada Geese and the greatest variance in numbers were sampled.

Results Between 1989 and 1999, the number of Canada Geese on land with over 5% water cover and on lowland with some water cover increased by on average 156%, an average rate of increase of 9.9% per annum. Southern Britain probably now holds a minimum of 82 000 Canada Geese. Between 1989 and 1999, the number of Greylag Geese on land with over 5% water cover and on lowland with some water cover increased by on average 214%, an average rate of increase of 12% per annum. Southern Britain probably now holds a minimum of 30 000 Greylag Geese.

Conclusion Maximum densities of Canada Geese may have been reached in high-density habitats but their numbers are still increasing very rapidly. Greylag Geese are increasing even more rapidly.     

Black Brant Harvest,Density Dependence,and Survival: A Record of Population Dynamics

ABSTRACT We analyzed 53 years of banding and band recovery data along with estimates of harvest and population size to assess the role of harvest and density dependence in survival patterns and population dynamics of black brant (Branta bernicla nigricans) over the period 1950–2003. The black brant population has declined steadily since complete annual surveys began in 1960, so the role of harvest in the dynamics of this population is of considerable interest. We used Brownie models implemented in Program MARK to analyze banding data. In some models, we incorporated estimated sport harvest to test hypotheses about the role of harvest in survival. We also examined the hypothesis of density-dependent regulation of mortality by incorporating estimates of population size as a covariate into models of survival. For a shorter period (1985–2003), we also assessed hypotheses about the role of subsistence harvest and predation as sources of mortality. The best supported model of variation in survival and band recovery allowed survival rates to vary among 2 age classes (juv, second-yr plus ad brant) and the 2 sexes. We constrained survival probabilities to be constant within decades but allowed them to vary among decades. We also constrained band recovery rates to be constant within decades and to vary in parallel among age and sex classes. We were limited to decade-specific estimates of survival and band recovery rates because some years before 1984 lacked any banding, and banding in some other years was sparse. A competitive model constrained survival estimates to be the same for males and females. No model containing harvest or population size was competitive with models lacking these covariates (relative quasi-Akaike's Information Criterion adjusted for small sample size [βQAIC_c] > 13). In the best supported model, band recovery rates declined from 0.038 ± 0.0028 (F) and 0.040 ± 0.0031 (M) to 0.007 ± 0.0007 (F) and 0.007 ± 0.0007 (M) between the 1950s and 2000s, a clear indication that harvest rates declined over this period. Survival rates increased from 0.70 ± 0.02 and 0.71 ± 0.02 for adult males and females, respectively, in the 1950s to 0.88 ± 0.009 and 0.88 ± 0.01 for males and females, respectively, in the 1990s. Survival rates in the 1990s were among the highest estimated for brant and did not increase in the 2000s with additional reductions in sport harvest. For the shorter data set from 1985 to 2003, models containing covariates for either sport or subsistence harvest were less competitive than models lacking these terms (βQAIC_c > 3). For the best model containing subsistence harvest, the estimate of β linking subsistence harvest to survival, although imprecisely estimated, was near zero (β = −0.04 ± 0.30), consistent with the hypothesis that subsistence harvest had little impact on survival during this period. We conclude that while harvest likely influenced survival and population dynamics in earlier decades, it is most likely that continued population decline at least since 1990 is a result of low recruitment.     

Multistate Mark–Recapture Model Selection Using Score Tests

Summary Although multistate mark–recapture models are recognized as important, they lack a simple model‐selection procedure. This article proposes and evaluates a step‐up approach to select appropriate models for multistate mark–recapture data using score tests. Only models supported by the data require fitting, so that over‐complicated model structures with too many parameters do not need to be considered. Typically only a small number of models are fitted, and the procedure is also able to identify parameter‐redundant and near‐redundant models. The good performance of the technique is demonstrated using simulation, and the approach is illustrated on a three‐region Canada goose data set. In this case, it identifies a new model that is much simpler than the best model previously considered for this application.     

High fidelity does not preclude colonization: range expansion of molting Black Brant on the Arctic coast of Alaska

High rates of site fidelity have been assumed to infer static distributions of molting geese in some cases. To test this assumption, we examined movements of individually marked birds to understand the underlying mechanisms of range expansion of molting Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain (ACP) of Alaska. The Teshekpuk Lake Special Area (TLSA) on the ACP was created to protect the primary molting area of Brant. When established in 1977, the TLSA was thought to include most, if not all, wetlands used by molting Brant on the ACP. From 2010 to 2013, we surveyed areas outside the TLSA and counted an average of 9800 Brant per year, representing 29–37% of all molting Brant counted on the ACP. We captured and banded molting Brant in 2011 and 2012 both within the TLSA and outside the TLSA at the Piasuk River Delta and Cape Simpson to assess movements of birds among areas across years. Estimates of movement rates out of the TLSA exceeded those into the TLSA, demonstrating overall directional dispersal. We found differences in sex and age ratios and proportions of adult females with brood patches, but no differences in mass dynamics for birds captured within and outside the TLSA. Overall fidelity rates to specific lakes (0.81, range = 0.49–0.92) were unchanged from comparable estimates obtained in the early 1990s. We conclude that Brant are dispersing from the TLSA into new molting areas while simultaneously redistributing within the TLSA, likely as a consequence of changes in relative habitat quality. Shifts in distribution resulted from colonization of new areas by young birds as well as low levels of directional dispersal of birds that previously molted in the TLSA. Based on combined counts, the overall number of molting Brant across the ACP has increased substantially.