Summary

1
For many species, human-induced disturbances can severely influence an individual's pay-off; however, energy-cost variations from different disturbance types have rarely been reported.

2
We evaluated the dynamic behavioural responses of staging greater snow geese Anser caerulescens atlanticus to different types of disturbance in southern Quebec, Canada, between 1997 and 2000. We specifically considered the impact of a unique measure, a spring conservation hunt implemented in agricultural habitats in 1999.

3
We tracked 237 radio-tagged females for 2764 h and recorded 697 take-offs following fortuitous disturbance, scaring and hunting in three regions characterized by different habitats. Geese used cornfields in south-western Quebec, Scirpus marshes and hayfields in the upper St Lawrence estuary, and Spartina marshes and hayfields in the lower estuary.

4
Overall, disturbance levels increased in the upper and lower estuary during years with hunting, mostly through an increase in hunting and scaring activities.

5
The probability of geese returning to a refuge after disturbance in agricultural habitats increased in years with hunting except in the corn-growing region. The short-term energy gain of geese resuming feeding after disturbance was less than before disturbance, and this difference was greater in years with hunting. Distances flown after disturbance decreased with flock size and were longer after scaring and hunting than after fortuitous disturbances in the Scirpus region.

6
Overall, habitat use varied among years and associated estimated energy gain decreased markedly in both years with hunting in the Spartina and corn-growing region, but did not change in the Scirpus region. Changes in behaviour due to disturbance, and especially those associated with hunting, probably contributed to the reduced body condition of staging greater snow geese during years with hunting.

7
Synthesis and applications. From a methodological viewpoint, we highlight the importance of tracking the behaviour of individual animals after disturbance to properly evaluate its impact. From a conservation perspective, we provide empirical arguments to limit the hunting of breeding waterfowl during their prenuptial migration in order to facilitate their fattening and forthcoming reproduction. From a management standpoint, we suggest that a side-effect of disturbance induced by spring hunting to control overabundant populations may be reduced fattening and breeding output among birds that survive. Together, these data emphasize further the importance of measuring the direct and indirect effects of disturbance rather than assuming effects from the incidence of the disturbance alone.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.0021-8901.2004.00928.x

The effects of disturbance on behaviour, habitat use and energy of spring staging snow geese

I review diet selection in grouse and waterfowl in the context of their herbivorous diets and discuss adaptations to herbivory in these groups. Both grouse and waterfowl prefer plant foods containing higher concentrations of protein than nonpreferred foods; grouse and small waterfowl include invertebrates in the diet to meet protein demands during periods of high tissue production. Grouse tend to avoid plant foods containing high concentrations of anti-herbivore compounds and the relative roles of these compounds versus nutrients in diet selection by grouse is presently unclear. Grouse and waterfowl have similar digestive morphology, except for the ceca, which are 5 times longer in grouse than in geese. Enlarged ceca are associated with improved nitrogen economy in grouse; evolution of these structures in geese may have been precluded by energetic costs of carrying enlarged ceca during migration.

Adaptations to and consequences of an herbivorous diet in grouse and waterfowl

Winter Diets and Nutrition of Midcontinental Lesser Snow Geese

We monitored evening flights of female Northern Pintails (Anas acuta) from Lacassine National Wildlife Refuge (NWR) in southwestern Louisiana during winters of 1991-1992 and 1992-1993. We analyzed the influence of female age, winter, and date within wintering period on three flight parameters: distance, duration, and departure time. Flight distance and duration increased with date within wintering period, and age differences in flight distance and duration were not consistent between winters. Females departed 12 min later, on average, on clear, moonlit evenings than on overcast, moonless evenings, and 4 min later when winds were light rather than heavy. After controlling for variation due to environmental conditions, immature females departed Lacassine NWR 1.3 min earlier, on average, than did adults. Flight parameters of females did not differ between hunting and non-hunting time periods. Estimated daily transit costs ranged from 27-54% of basal met- abolic rate, 7-19% of daily energy expenditure, and 8-20% of daily dietary intake of rice (Oryza sativa). Our findings that flight distance and duration increased with date within wintering period were consistent with predictions of refuging theory, but alternative hy- potheses also could explain these results. Evening flights of Northern Pintails roosting on Lacassine NWR were greater in distance and duration than those reported for most other species of wintering waterfowl. We recommend that proximity of refuges to feeding sites be considered in conservation and management plans for wintering Northern Pintails and other refuging waterfowl.

http://www.rnr.lsu.edu/people/afton/PubPDFs/Condor%2098_810-819.pdf

Evening flights of female northern pintails from a major roost site

Summary

1. We examined impacts of nutrient loading, particularly of nitrogen and phosphorus, from greater snow geese (Chen caerulescens atlantica) on a reservoir in south-eastern Pennsylvania, U.S.A. Approximately 100 000 geese use the reservoir for 2–6 weeks prior to their spring migration northward.



2. We estimated the magnitude of nutrient loading by geese during their presence and compared that to surface input and output rates. We also conducted nutrient limitation bioassay experiments to examine patterns of algal nutrient limitation upstream and downstream of the reservoir.



3. During their presence from 1 February to 27 March 2001, snow geese contributed 85–93% of the phosphorus and 33–44% of the nitrogen loaded to the reservoir. Both nutrients were exported from the reservoir slowly rather than as a quick pulse. Consequently, phosphorus concentrations in the outflow were higher than in the inflow from February to the end of July. However, nitrogen concentrations were consistently lower in the outflow than the inflow.



4. Nutrient limitation bioassays conducted in June and July indicated that primary production in the outflow was limited by nitrogen whereas the inflow was co-limited by nitrogen and phosphorus. Further downstream from the reservoir, primary production was consistently phosphorus limited. Therefore, nitrogen limitation persisted long after the geese had left, but was relatively localised.

Impact of migratory snow geese on nitrogen and phosphorus dynamics in a freshwater reservoir

Time-activity budgets for fall-migrating lesser snow geese (Anser caerulescens) were studied at DeSoto National Wildlife Refuge (NWR) during 1976-77. Temperature, wind speed and direction, time of day, seasonal period, and habitat type significantly affected time spent in various activities. Geese spent about 13% of each 24-hour day feeding, primarily on waste corn. Feeding was most intense in early morning and late afternoon. Differences in feeding activity among seasonal periods were evidently caused by changes in weather conditions, food availability, and goose population size. Less than half of an esti- mated 500 metric tons of corn required by the geese during fall was potentially available within refuge boundaries. Although ample corn was available within 8 km of the refuge, fall harvest and plowing caused large seasonal fluctuations in availability of waste corn.

http://www.jstor.org/stable/pdfplus/3808550.pdf

Resource use and behavior of migrating snow geese1

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Resource use and behavior of migrating snow geese1