Catherine Bajzak - Academia.edu (original) (raw)
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Papers by Catherine Bajzak
Marine Ecology Progress Series, 2009
Canadian Journal of Zoology, Nov 1, 2011
Harp seals ( Pagophilus groenlandicus (Erxleben, 1777)) required drifting pack-ice for birth, nur... more Harp seals ( Pagophilus groenlandicus (Erxleben, 1777)) required drifting pack-ice for birth, nursing, and as a resting platform for neonates after weaning. Data on the yearly location of whelping patches in the Gulf of St. Lawrence collected between 1977 and 2011 were combined with ice cover data (thickness and duration) to examine whether female harp seals actively select particular ice features as a breeding platform and to describe how these ice features have varied over the last 40 years at three spatial scales: the entire Gulf of St. Lawrence, the southern gulf, and the “traditional whelping area” within the southern Gulf. From our analyses, harp seals prefer the thickest ice stages available in the Gulf: grey–white and first-year ice. Lower than normal ice coverage years were more frequent for the required grey–white and first-year ice than for the total ice cover and less frequent at the “traditional whelping area” scale close to the northwestern coast of the Magdalen Islands than at the Gulf of St. Lawrence scale. The frequency of light ice years increased and the duration of the ice season decreased throughout the last decade. Our study showed that the temporal availability and the spatial distribution of the suitable ice are important when evaluating the effect of changes in ice conditions rather than overall ice extent.
Polar Biology, 2012
Over the last few decades, the period of ice cover in Hudson Bay has decreased, owing to climate ... more Over the last few decades, the period of ice cover in Hudson Bay has decreased, owing to climate warming, with breakup occurring approximately 3 weeks earlier than it did 30 years ago. The trend towards lengthening of the open water season has led to speculation that ringed seal numbers would decline, but then harbour seals might become numerous enough to replace ringed seals in the diet of polar bears. The movement patterns of 18 harbour seals equipped with satellite-linked transmitters in the Churchill River estuary (western Hudson Bay) were examined, as well as the dive behaviour of 11 of these seals. During the ice-free period, seals followed a general central place-foraging strategy, making repeated trips between their haul-out site in the Churchill River estuary and nearshore areas (\20 km) near the river mouth and estuary. Seal behaviour changed significantly as ice started to form along the coast of western Hudson Bay: animals remained significantly farther from the Churchill River haul-out site and from the coast and performed longer and deeper dives. However, throughout the entire tracking period, whether ice was present or not, all animals restricted their movements to a narrow band of shallow coastal waters (\50 m depth) along a 600-km stretch of the western Hudson Bay coastline, centred on the Churchill River estuary haul-out site. This natural self-limitation to nearshore shallow waters could restrict the potential for the population to increase in size and replace ringed seals as a primary energy resource for polar bears.
Ethology, 2008
Early breeding is associated with greater reproductive success in many species. In king penguins,... more Early breeding is associated with greater reproductive success in many species. In king penguins, Aptenodytes patagonicus, laying extends for 6 mo. Early breeders may fledge a single chick at best, but late breeders virtually never fledge a chick. For early and late breeders, we compared colored ornaments known to be important in mate choice: yellow–orange feathers of the breast and auricular areas, and an ultraviolet and yellow–orange beak spot. Our purpose was to discern differences between males and females in this highly sexually monomorphic species, as well as to discern whether colored ornaments are more important for the more successful early breeders (aspects of color were hue, chroma, and brightness). For this, we weighed and measured 130 penguins. Early males had greater reflectance of ultraviolet color from the beak spot than did early females and late breeders of both sexes, and the early males were heavier and in better condition than late breeding males or females. Lat...
Proceedings of the Royal Society B: Biological Sciences, 2005
After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea... more After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea exulans) are able to pinpoint a specific remote island where their nests are located. This impressive navigation ability is highly precise but its nature is mysterious. Here we examined whether albatrosses rely on the perception of the Earth's magnetic field to accomplish this task. We disturbed the perception of the magnetic field using mobile magnets glued to the head of nine albatrosses and compared their performances with those of 11 control birds. We then used satellite telemetry to monitor their behaviour. We found that the ability of birds to home to specific nest sites was unimpaired by this manipulation. In particular, experimental and control birds did not show significant differences with respect to either foraging trip duration, or length, or with respect to homing straightness index. Our data suggest that wandering albatrosses do not require magnetic cues to navigate ba...
Animal Behaviour, 2004
Previous work has shown that blue petrels need olfaction to home. We investigated whether they al... more Previous work has shown that blue petrels need olfaction to home. We investigated whether they also recognize an olfactory signature of their own nest. We performed T-maze experiments in which maze arms were connected with the subject bird's burrow and with the burrow of a conspecific neighbour. Of 23 birds, 16 were able to recognize the arm leading to their own burrow. In a second experiment, we positioned the maze in front of the subject's burrow but the maze arms were closed and did not enter the burrow. Consequently, no burrow odours could be sensed by the bird. In this case, 85% of birds (17 of 20) failed to choose, suggesting that petrels were not motivated to choose by positional cues in the absence of odour cues. We explored this idea further by performing a homing experiment whereby homing birds had to relocate an artificially displaced burrow entrance. Blue petrels homed, ignoring the natural burrow entrance and using the new artificial one. The ability to smell their own burrow allows blue petrels to return to the colony at night and to find the correct nest.
Proceedings of the Royal Society B: Biological Sciences, 2005
After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea... more After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea exulans) are able to pinpoint a specific remote island where their nests are located. This impressive navigation ability is highly precise but its nature is mysterious. Here we examined whether albatrosses rely on the perception of the Earth's magnetic field to accomplish this task. We disturbed the perception of the magnetic field using mobile magnets glued to the head of nine albatrosses and compared their performances with those of 11 control birds. We then used satellite telemetry to monitor their behaviour. We found that the ability of birds to home to specific nest sites was unimpaired by this manipulation. In particular, experimental and control birds did not show significant differences with respect to either foraging trip duration, or length, or with respect to homing straightness index. Our data suggest that wandering albatrosses do not require magnetic cues to navigate back to their nesting sites.
Marine Ecology Progress Series, 2009
Canadian Journal of Zoology, Nov 1, 2011
Harp seals ( Pagophilus groenlandicus (Erxleben, 1777)) required drifting pack-ice for birth, nur... more Harp seals ( Pagophilus groenlandicus (Erxleben, 1777)) required drifting pack-ice for birth, nursing, and as a resting platform for neonates after weaning. Data on the yearly location of whelping patches in the Gulf of St. Lawrence collected between 1977 and 2011 were combined with ice cover data (thickness and duration) to examine whether female harp seals actively select particular ice features as a breeding platform and to describe how these ice features have varied over the last 40 years at three spatial scales: the entire Gulf of St. Lawrence, the southern gulf, and the “traditional whelping area” within the southern Gulf. From our analyses, harp seals prefer the thickest ice stages available in the Gulf: grey–white and first-year ice. Lower than normal ice coverage years were more frequent for the required grey–white and first-year ice than for the total ice cover and less frequent at the “traditional whelping area” scale close to the northwestern coast of the Magdalen Islands than at the Gulf of St. Lawrence scale. The frequency of light ice years increased and the duration of the ice season decreased throughout the last decade. Our study showed that the temporal availability and the spatial distribution of the suitable ice are important when evaluating the effect of changes in ice conditions rather than overall ice extent.
Polar Biology, 2012
Over the last few decades, the period of ice cover in Hudson Bay has decreased, owing to climate ... more Over the last few decades, the period of ice cover in Hudson Bay has decreased, owing to climate warming, with breakup occurring approximately 3 weeks earlier than it did 30 years ago. The trend towards lengthening of the open water season has led to speculation that ringed seal numbers would decline, but then harbour seals might become numerous enough to replace ringed seals in the diet of polar bears. The movement patterns of 18 harbour seals equipped with satellite-linked transmitters in the Churchill River estuary (western Hudson Bay) were examined, as well as the dive behaviour of 11 of these seals. During the ice-free period, seals followed a general central place-foraging strategy, making repeated trips between their haul-out site in the Churchill River estuary and nearshore areas (\20 km) near the river mouth and estuary. Seal behaviour changed significantly as ice started to form along the coast of western Hudson Bay: animals remained significantly farther from the Churchill River haul-out site and from the coast and performed longer and deeper dives. However, throughout the entire tracking period, whether ice was present or not, all animals restricted their movements to a narrow band of shallow coastal waters (\50 m depth) along a 600-km stretch of the western Hudson Bay coastline, centred on the Churchill River estuary haul-out site. This natural self-limitation to nearshore shallow waters could restrict the potential for the population to increase in size and replace ringed seals as a primary energy resource for polar bears.
Ethology, 2008
Early breeding is associated with greater reproductive success in many species. In king penguins,... more Early breeding is associated with greater reproductive success in many species. In king penguins, Aptenodytes patagonicus, laying extends for 6 mo. Early breeders may fledge a single chick at best, but late breeders virtually never fledge a chick. For early and late breeders, we compared colored ornaments known to be important in mate choice: yellow–orange feathers of the breast and auricular areas, and an ultraviolet and yellow–orange beak spot. Our purpose was to discern differences between males and females in this highly sexually monomorphic species, as well as to discern whether colored ornaments are more important for the more successful early breeders (aspects of color were hue, chroma, and brightness). For this, we weighed and measured 130 penguins. Early males had greater reflectance of ultraviolet color from the beak spot than did early females and late breeders of both sexes, and the early males were heavier and in better condition than late breeding males or females. Lat...
Proceedings of the Royal Society B: Biological Sciences, 2005
After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea... more After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea exulans) are able to pinpoint a specific remote island where their nests are located. This impressive navigation ability is highly precise but its nature is mysterious. Here we examined whether albatrosses rely on the perception of the Earth's magnetic field to accomplish this task. We disturbed the perception of the magnetic field using mobile magnets glued to the head of nine albatrosses and compared their performances with those of 11 control birds. We then used satellite telemetry to monitor their behaviour. We found that the ability of birds to home to specific nest sites was unimpaired by this manipulation. In particular, experimental and control birds did not show significant differences with respect to either foraging trip duration, or length, or with respect to homing straightness index. Our data suggest that wandering albatrosses do not require magnetic cues to navigate ba...
Animal Behaviour, 2004
Previous work has shown that blue petrels need olfaction to home. We investigated whether they al... more Previous work has shown that blue petrels need olfaction to home. We investigated whether they also recognize an olfactory signature of their own nest. We performed T-maze experiments in which maze arms were connected with the subject bird's burrow and with the burrow of a conspecific neighbour. Of 23 birds, 16 were able to recognize the arm leading to their own burrow. In a second experiment, we positioned the maze in front of the subject's burrow but the maze arms were closed and did not enter the burrow. Consequently, no burrow odours could be sensed by the bird. In this case, 85% of birds (17 of 20) failed to choose, suggesting that petrels were not motivated to choose by positional cues in the absence of odour cues. We explored this idea further by performing a homing experiment whereby homing birds had to relocate an artificially displaced burrow entrance. Blue petrels homed, ignoring the natural burrow entrance and using the new artificial one. The ability to smell their own burrow allows blue petrels to return to the colony at night and to find the correct nest.
Proceedings of the Royal Society B: Biological Sciences, 2005
After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea... more After making foraging flights of several thousands of kilometres, wandering albatrosses (Diomedea exulans) are able to pinpoint a specific remote island where their nests are located. This impressive navigation ability is highly precise but its nature is mysterious. Here we examined whether albatrosses rely on the perception of the Earth's magnetic field to accomplish this task. We disturbed the perception of the magnetic field using mobile magnets glued to the head of nine albatrosses and compared their performances with those of 11 control birds. We then used satellite telemetry to monitor their behaviour. We found that the ability of birds to home to specific nest sites was unimpaired by this manipulation. In particular, experimental and control birds did not show significant differences with respect to either foraging trip duration, or length, or with respect to homing straightness index. Our data suggest that wandering albatrosses do not require magnetic cues to navigate back to their nesting sites.