NOCTURNAL FORAGING BEHAVIOR OF WINTERING SURF SCOTERS AND WHITE-WINGED SCOTERS

Abstract We studied the nocturnal foraging behavior of Surf Scoters (Melanitta perspicillata) and White-winged Scoters (Melanitta fusca) during winter in coastal British Columbia, Canada. Using radio telemetry, we collected nocturnal and diurnal data documenting the frequency of foraging dives and the location of scoters in relation to their intertidal foraging grounds. We found that dive foraging rarely occurred during nocturnal periods for either species. Only 2% of nocturnal observation blocks for both scoter species contained diving, compared with 98% of diurnal observation blocks. This corresponded to an average of only 0.1 min spent underwater per half-hour observation block during the night and over 7 min during the day. Both species of scoters were located farther offshore and in deeper waters during nocturnal hours, indicating that they were not using intertidal foraging areas at night. Our results suggest that Surf Scoters and White-winged Scoters face daylight-imposed limits on the amount of available foraging time. These potential day-length restrictions should be considered when reviewing human activities that potentially alter the amount of available foraging time or food supplies in winter habitats. Comportamiento de Forrajeo Nocturno de Melanitta perspicillata y M. fusca Resumen. Se estudió el comportamiento de forrajeo nocturno de Melanitta perspicillata y M. fusca durante el invierno en la costa de British Columbia. Utilizando radio-telemetría, se colectaron datos nocturnos y diurnos sobre la frecuencia de buceos para alimentarse y la ubicación de las aves con relación a la zona intermareal. Se encontró que los buceos nocturnos son infrecuentes para ambas especies. Sólo en el 2% de las observaciones nocturnas de ambas especies se presentaron instancias de buceo, en comparación con el 98% de las observaciones diurnas. Esto corresponde a un promedio de 0.11 minutos bajo el agua por cada 30 minutos de observación durante la noche y más de 7 minutos durante el día. Ambas especies se ubicaron más alejadas de la costa y en aguas más profundas durante la noche, indicando que los individuos no utilizaron zonas intermareales durante este periodo. Estos resultados sugieren que M. perspicillata y M. fusca enfrentan restricciones en el número de horas disponibles para alimentarse en función de la cantidad de luz. El efecto de la duración del día debe ser considerado cuando se estudia el impacto de actividades humanas que pueden alterar el tiempo disponible para forrajeo o la cantidad de alimento durante el invierno.

[1]  G. Pyke.  Optimal Foraging Theory: A Critical Review , 1984 .

[2]  Gary C. White,et al.  Analysis of Wildlife Radio-Tracking Data , 1990 .

[3]  Joep J. de Leeuw,et al.  Diving costs as a component of daily energy budgets of aquatic birds and mammals: generalizing the inclusion of dive-recovery costs demonstrated in tufted ducks , 1996 .

[4]  P. Drapeau,et al.  THE OCCURRENCE AND ADAPTIVE SIGNIFICANCE OF NOCTURNAL HABITS IN WATERFOWL , 1992 .

[5]  T. Bowman,et al.  CORRELATES OF HARLEQUIN DUCK DENSITIES DURING WINTER IN PRINCE WILLIAM SOUND, ALASKA , 2000 .

[6]  A. Kacelnik,et al.  Optimal Foraging and Beyond: How Starlings Cope with Changes in Food Availability , 1998, The American Naturalist.

[7]  J. Lovvorn,et al.  Diet and body condition of spectacled eiders wintering in pack ice of the Bering Sea , 2003, Polar Biology.

[8]  W. D. Klimstra,et al.  Activity Patterns of Canada Geese during Winter , 1972 .

[9]  Coping with darkness and low temperatures: foraging strategies in Steller's eiders, Polysticta stelleri, wintering at high latitudes , 2001 .

[10]  E. Nol,et al.  Foraging behaviour of American oystercatchers in response to declining prey densities , 1997 .

[11]  S. Wanless,et al.  Diving patterns of full-grown and juvenile rock shags , 1991 .

[12]  Jean-Carlo Pedroli.  Activity and time budget of Tufted Ducks on Swiss lakes during winter , 1982 .

[13]  C. Griffin,et al.  FEEDING BEHAVIOR AND FOOD HABITS OF WINTERING HARLEQUIN DUCKS AT SHEMYA ISLAND, ALASKA , 2000 .

[14]  Gary C. White,et al.  Error in telemetry studies: Effects of animal movement on triangulation , 1990 .

[15]  M. Guillemette.  The effect of time and digestion constraints in Common Eiders while feeding and diving over Blue Mussel beds , 1998 .

[16]  David R. Anderson,et al.  Model selection and multimodel inference : a practical information-theoretic approach , 2003 .

[17]  Gary C. White,et al.  Accessing accuracy of a radiotelemetry system for estimating animal locations , 1985 .

[18]  R. Littell.  SAS System for Mixed Models , 1996 .

[19]  R. Ydenberg,et al.  The role of energy intake rate in prey and habitat selection of common eiders Somateria mollissima in winter : a risk-sensitive interpretation , 1992 .

[20]  Eric C. Palm,et al.  Surf Scoter (Melanitta perspicillata) , 1998 .

[21]  J. Coulson,et al.  Marine birds : their feeding ecology and commercial fisheries relationships , 1985 .

[22]  S. Baird,et al.  The birds of North America , 1974 .

[23]  D. W. Sparks,et al.  RADIO TELEMETRY DOCUMENTS 24-HOUR FEEDING ACTIVITY OF WINTERING LESSER SCAUP , 1996 .

[24]  M. Guillemette,et al.  Habitat selection by common eiders in winter and its interaction with flock size , 1993 .

[25]  A. Poole,et al.  White-winged Scoter (Melanitta fusca) , 1997 .

[26]  L. Nilsson.  Food-seeking activity of south Swedish diving ducks in the non-breeding season , 1970 .

[27]  K. Erikstad,et al.  BEHAVIORAL RESPONSES TO DECREASING DAY LENGTH IN WINTERING SEA DUCKS , 2000 .

[28]  Guy Beauchamp.  Diving Behavior in Surf Scoters and Barrow's Goldeneyes , 1992 .

[29]  D. Esler,et al.  Surgical and immediate post-release mortality of harlequin ducks (Histrionicus histrionicus) implanted with abdominal radio transmitters with percutaneous antennae. , 1999, Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians.