“…Among five recent studies in seabirds, three have shown a compensatory response from the partners of handicapped birds [10], [11], [80] and two did not find such a response ([66] and our own). Consequently, it seems that compensatory behaviour is not consistent and may depend on the overall availability of food in a given year.…”
Section: Discussioncontrasting
confidence: 55%
“…Chicks of handicapped parents grew slower because handicapped parents fed their chicks less (Figs. 1, 2), as is the case in penguins ([65], but see [66]). Handicapping had a smaller effect on chick wing growth, which is largely maintained during very poor years at the expense of body growth, as wing growth is essential for fledging [67], [68].…”
Section: Discussionmentioning
confidence: 84%
“…Because they integrate information over large oceanic regions, seabirds are useful indicators of marine changes [94], [95], [96], [9]. Experimental studies, such as our own and those of Gill et al (2002), are useful for pinpointing what metrics are most useful and for understanding the mechanisms underlying correlations between environmental proxies and their impacts on seabirds [11], [12], [66], [83]. For example, due to earlier ice break-up in Hudson Bay, murres at our study site have switched from larger to smaller prey items and chicks grow less quickly [43], [44], [45]; energy costs for delivery of many small items is greater than a single large item [46].…”
Life history theory predicts that parents will balance benefits from investment in current offspring against benefits from future reproductive investments. Long-lived organisms are therefore less likely to increase parental effort when environmental conditions deteriorate. To investigate the effect of decreased foraging capacity on parental behaviour of long-lived monogamous seabirds, we experimentally increased energy costs for chick-rearing thick-billed murres (Uria lomvia). Handicapped birds had lighter chicks and lower provisioning rates, supporting the prediction that long-lived animals would pass some of the costs of impaired foraging ability on to their offspring. Nonetheless, handicapped birds spent less time underwater, had longer inter-dive surface intervals, had lower body mass, showed lower resighting probabilities in subsequent years and consumed fewer risky prey items. Corticosterone levels were similar between control and handicapped birds. Apparently, adults shared some of the costs of impaired foraging, but those costs were not measurable in all metrics. Handicapped males had higher plasma neutral lipid concentrations (higher energy mobilisation) and their chicks exhibited lower growth rates than handicapped females, suggesting different sex-specific investment strategies. Unlike other studies of auks, partners did not compensate for handicapping, despite good foraging conditions for unhandicapped birds. In conclusion, parental murres and their offspring shared the costs of experimentally increased foraging constraints, with females investing more than males.
“…Among five recent studies in seabirds, three have shown a compensatory response from the partners of handicapped birds [10], [11], [80] and two did not find such a response ([66] and our own). Consequently, it seems that compensatory behaviour is not consistent and may depend on the overall availability of food in a given year.…”
Section: Discussioncontrasting
confidence: 55%
“…Chicks of handicapped parents grew slower because handicapped parents fed their chicks less (Figs. 1, 2), as is the case in penguins ([65], but see [66]). Handicapping had a smaller effect on chick wing growth, which is largely maintained during very poor years at the expense of body growth, as wing growth is essential for fledging [67], [68].…”
Section: Discussionmentioning
confidence: 84%
“…Because they integrate information over large oceanic regions, seabirds are useful indicators of marine changes [94], [95], [96], [9]. Experimental studies, such as our own and those of Gill et al (2002), are useful for pinpointing what metrics are most useful and for understanding the mechanisms underlying correlations between environmental proxies and their impacts on seabirds [11], [12], [66], [83]. For example, due to earlier ice break-up in Hudson Bay, murres at our study site have switched from larger to smaller prey items and chicks grow less quickly [43], [44], [45]; energy costs for delivery of many small items is greater than a single large item [46].…”
Life history theory predicts that parents will balance benefits from investment in current offspring against benefits from future reproductive investments. Long-lived organisms are therefore less likely to increase parental effort when environmental conditions deteriorate. To investigate the effect of decreased foraging capacity on parental behaviour of long-lived monogamous seabirds, we experimentally increased energy costs for chick-rearing thick-billed murres (Uria lomvia). Handicapped birds had lighter chicks and lower provisioning rates, supporting the prediction that long-lived animals would pass some of the costs of impaired foraging ability on to their offspring. Nonetheless, handicapped birds spent less time underwater, had longer inter-dive surface intervals, had lower body mass, showed lower resighting probabilities in subsequent years and consumed fewer risky prey items. Corticosterone levels were similar between control and handicapped birds. Apparently, adults shared some of the costs of impaired foraging, but those costs were not measurable in all metrics. Handicapped males had higher plasma neutral lipid concentrations (higher energy mobilisation) and their chicks exhibited lower growth rates than handicapped females, suggesting different sex-specific investment strategies. Unlike other studies of auks, partners did not compensate for handicapping, despite good foraging conditions for unhandicapped birds. In conclusion, parental murres and their offspring shared the costs of experimentally increased foraging constraints, with females investing more than males.
“…Although long-living seabirds are not expected to increase their breeding investment in response to a reduction in parental care by the partner (Beaulieu et al 2009), Harding et al (2009c) suggested that little auks have the capacity to increase the provision rate in response to reduced efforts of the mate. A possible explanation of this compensatory behaviour is an increased chick begging behaviour in response to increased corticosterone secretion (Kitayski et al 2001).…”
We studied the effects of loggers attached to chick-rearing little auks (Alle alle) on their daily time budget (proportion of time spent in the colony and at sea), foraging activity (duration and proportion of long and short foraging flights), chick provisioning rate and their growth and development on Spitsbergen. We found that experimental parent birds performed shorter but more frequent long foraging flights and reduced the frequency of short foraging flights. They spent more time at the colony and reduced chick provisioning rate compared to control birds. Nestlings reared by experimental parents weighed significantly less at their middle, peak and fledging age and departed colony later than chicks of control parents. Little auks depend on energy-rich copepods associated with cold Arctic waters and are expected to face the climate-induced worsening of the foraging conditions, which may have negative impact on their time/energy budget and survival. The study may help to determine the level of extra effort little auks need to invest to breed successfully.
“…A recent study conducted by Beaulieu et al (2009) showed that Adélie penguins handicapped by back-mounted, dummy Plexiglas devices performed longer foraging trips. Here, to examine such instrumentation effects, we monitored (via visual observations of the nest every 2h) the durations of foraging trips of 6 unequipped male control birds and then compared them with control birds equipped with loggers.…”
Hormones link environmental stimuli to the behavioural and/or physiological responses of organisms. The release of corticosterone has major effects on both energy mobilization and its allocation among the various requirements of an individual, especially regarding survival and reproduction. We therefore examined the effects of experimentally elevated baseline corticosterone levels on the foraging behaviour of Adélie penguins Pygoscelis adeliae during chickrearing. We monitored the at-sea behaviour of corticosterone-implanted and control male birds using time-depth recorders, and monitored the effects of corticosterone treatment on their body conditions as well as their chicks' body masses and survival. Bio-logged data were examined via traditional measures of diving behaviour as well as fractal analysis as an index of behavioural complexity. Corticosterone administration caused a transient decrease in both overall foraging effort (i.e. reductions in the duration of at-sea trips, the time spent diving and the number of dives performed) and foraging complexity. In contrast, per-dive performance indices suggested an increase in both efficiency and prey pursuit rates. Ultimately, however, we observed no short-term effects of treatment on adult body condition and chick body mass and survival. We conclude that under higher corticosterone levels, sequences of behaviour may become more structured and periodic, as observed in treated birds. The increased energy allocation to dive-scale behaviours observed in treated birds might then reflect an adjustment to intrinsic constraints allowing reductions in energy expenditure at the trip-scale. This study highlights the utility of using both traditional and fractal analyses to better understand scale-dependent responses of animals to energetic and various other environmental challenges.
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