Increased energy expenditure by a seabird in response to higher food abundance

Abstract

Variability in forage fish abundance strongly affects seabird behavior and reproductive success, although details of this relationship are unclear. During 1997 and 1998, we measured (1) daily energy expenditure (DEE) of 80 parent black-legged kittiwakes Rissa tridactyla at 2 colonies in Prince William Sound, Alaska (North Icy Bay and Shoup Bay), (2) abundance of surface-schooling forage fishes within the foraging range of each colony, and (3) diet composition, energy delivery rates to nestlings, and reproductive success of kittiwakes at these same colonies. Female DEE was highest at North Icy Bay in 1998, while male DEE did not differ by colony year. Abundances of Pacific herring Clupea pallasi and sand lance Ammodytes hexapterus were highest near North Icy Bay in 1998 and nearly equal in density, although Age 1+ herring comprised the majority of the diet there. Energy delivery rates to nestlings, nestling growth rates, and productivity were also highest at North Icy Bay in 1998. We suggest that female kittiwakes responded to the increased abundance of Age 1+ herring near North Icy Bay in 1998 by increasing their DEE, which in turn positively affected reproductive success. Given that adult kittiwakes have been shown to suffer decreased survival as a response to increased energy expenditure during brood rearing, the positive correlation we observed between increased abundance of a high quality food source, parental effort, and productivity is consistent with maximizing lifetime reproductive success. The lack of a response in male DEE suggests that broodrearing roles in kittiwakes differ between genders.

Trade-offs in prey quality and quantity revealed through the behavioral compensation of breeding seabirds

“…Compensation can take a variety of forms, such as a bimodal foraging strategy (Chaurand & Weimerskirch 1994, Weimerskirch et al 2003, Welcker et al 2009a), individual differences in foraging habitats (Elliott et al 2008b(Elliott et al , 2009, or simply an increase in trip duration and/or foraging distance (Suryan et al 2002, Burke & Montevecchi 2009, Pichegru et al 2010. In some cases adults expend more energy to increase feeding rates and/or take higher quality prey (Jodice et al 2006, Deagle et al 2008, Welcker et al 2009b; but see Welcker et al 2010). To successfully fledge chicks, any seabird must ultimately maintain a minimum rate of energy (calories from food) delivery to the colony.…”

“…To successfully fledge chicks, any seabird must ultimately maintain a minimum rate of energy (calories from food) delivery to the colony. From the offspring's perspective, therefore, energy delivery rate can be treated as a provisioning currency, and this has been used to measure the net result of provisioning (Lewis et al 2003, Weimerskirch et al 2003, Jodice et al 2006. Energy return rate to chicks can be disarticulated into 2 variables: (1) energy per meal, reflecting the type and quality of prey, and (2) meal delivery rate, relating both the quantity of prey delivered and the time invested in provisioning.…”

Food web interactions in the southwestern Barents Sea: black-legged kittiwakes Rissa tridactyla respond negatively to an increase in herring Clupea harengus

“…The fact that increased herring abundance is probably acting negatively on black-legged kittiwakes at Hornøya is the reverse of the positive effect found at some colonies in Prince William Sound, Alaska, where an increased abundance of juvenile Pacific herring Clupea pallasi resulted in higher delivery rates, chick growth and breeding success (Suryan & Irons 2001, Jodice et al 2006a). This was, however, at the expense of female parental effort, which increased with juvenile herring abundance, though probably not at a rate high enough to compromise lifetime reproductive success (Jodice et al 2006a).…”

“…Other colonies in Prince William Sound had periodical access to both sand eels (e.g. Pacific sand lance Ammodytes hexapterus) and capelin and substantial variation in annual rates of productivity were associated with diet composition (Jodice et al 2006a). When prey were close to the colony, production was high, but when prey was difficult to access breeding failure was common (Jodice et al 2006b).…”

“…This was, however, at the expense of female parental effort, which increased with juvenile herring abundance, though probably not at a rate high enough to compromise lifetime reproductive success (Jodice et al 2006a). The positive effect of increases in juvenile herring in Prince William Sound is in contrast to the negative effect found in this study.…”