812 [Auk, Vol. 117 Short Communications The Auk 117(3):812–817, 2000 Body-mass Dynamics of King Eiders During Incubation DANA K. KELLETT 1,3 AND RAY T. ALISAUSKAS 1,2 1 Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada; and 2 Prairie and Northern Wildlife Research Center, Canadian Wildlife Service, 115 Perimeter Road, Saskatoon, Saskatchewan S7N 0X4, Canada Several studies have demonstrated the importance of maintaining parental body reserves to successful- ly complete incubation or to raise offspring without affecting parental survival (e.g. Tombre and Erikstad 1996, Merila ¨ and Wiggins 1997, Zicus 1997). Re- straint in use of reserves could be favored if females with greater reserves after laying had higher repro- ductive success or survival. Erikstad and Tveraa (1995) suggested that optimal clutch size in Common Eiders (Somateria mollissima) is determined by an in- teraction between allocation of endogenous reserves to egg production and energy needed for incubation and brood rearing. Depletion of reserves before hatching may lead to nest failure through nest aban- donment or decreased nest attentiveness. Moreover, high nest attentiveness may reduce predation by re- ducing the amount of time that nests are unattended and by reducing incubation duration (Milne 1976, Aldrich and Raveling 1983). Nest failure during in- cubation, therefore, may be a consequence of nest abandonment or predation, either of which may be linked to female body condition. Gloutney and Clark (1991) found that female Mal- lards (Anas platyrhynchos) and Northern Shovelers (A. clypeata) that nested successfully were heavier than unsuccessful females, but this pattern was ab- sent in Blue-winged Teal (A. discors). Canvasbacks (Aythya valisineria) and Redheads (Aythya americana) used stored reserves during egg production and in- cubation, but body mass during late incubation pre- dicted nesting success only for yearling Canvasbacks (Arnold et al. 1995). Blums et al. (1997) investigated this hypothesis in a large sample of Common Po- chards (Aythya ferina) and Tufted Ducks (A. fuligula); late-incubation body mass predicted nesting success in Tufted Ducks and adult Common Pochards, but not in yearling Common Pochards. Hence, whereas all three studies documented effects of body mass on nesting success, in at least some species and/or age groups, these effects did not apply. Because arctic-nesting species contend with colder temperatures and possibly lower food availability 3 Present address: Prairie and Northern Wildlife Research Center, Canadian Wildlife Service, 115 Pe- rimeter Road, Saskatoon, Saskatchewan S7N 0X4, Canada. E-mail: dana.kellett@ec.gc.ca (Ankney and MacInnes 1978, Gloutney et al. 2000), they may rely more heavily on endogenous reserves during incubation than do temperate-nesting spe- cies. In any environment, stability of thermal and gaseous environments for developing embryos re- quires high incubation constancy (Drent 1975). Low- er ambient temperatures can increase rates of egg cooling (Caldwell and Cornwell 1975, Afton and Paulus 1992), which may make high incubation con- stancy crucial for embryonic development and fe- male energy conservation, especially in arctic envi- ronments. Moreover, if food is scarce during incu- bation, arctic-nesting waterfowl may have little choice but to rely on stored reserves. In contrast, en- dogenous reserves meet only a small fraction of en- ergy requirements in temperate-nesting waterfowl (Afton and Paulus 1992), either because food is abun- dant on nesting areas, or because milder conditions allow lower nest attendance without compromising the nest environment. The importance of endoge- nous reserves for successful incubation has been demonstrated in arctic-nesting Lesser Snow Geese (Chen caerulescens; Ankney and MacInnes 1978) and coastal-nesting Common Eiders (Korschgen 1977). Successful Snow Geese collected late in incubation weighed more than did failed nesters, and both weighed more than birds that had starved to death on their nests (Ankney and MacInnes 1978). Similar- ly, heavy Common Eider females were less likely to abandon nests than were lighter females (Korschgen 1977). Lesser Snow Geese and Ross’s Geese (Chen ros- sii) acquire few nutrients between arrival on the breeding grounds and the end of incubation (An- kney and MacInnes 1978, Gloutney et al. 2000), likely because little vegetation is available to foraging geese in large colonies. Food appears to be abundant for breeding Common Eiders, yet females feed little during laying and incubation (Korschgen 1977). We examined body-mass dynamics of King Eiders (Somateria spectabilis) to evaluate the degree to which females relied on endogenous reserves during incu- bation. We assumed that female King Eiders would exhibit high levels of nest attentiveness owing to low ambient temperatures and therefore predicted that they would rely more on endogenous reserves dur- ing incubation than do temperate-nesting species. We were especially interested in how depletion of re- serves influenced nesting success, and we predicted Downloaded from https://academic.oup.com/auk/article/117/3/812/5561649 by guest on 26 September 2022