Rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata breeding in a seasonal environment

Abstract

2004. Rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata breeding in a seasonal environment. Á/ J. Avian Biol. 35: 224 Á/236.We removed first eggs from early-laying females to measure rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata at Triangle Island, British Columbia, Canada. Based on egg size and composition, the investment that Cassin's auklets made in first eggs was very close to that predicted from adult body mass, whereas rhinoceros auklets invested more. In both species, a high percentage of females relaid (90% of Cassin's and 87% of rhinoceros auklets). Breeding success declined weakly with later laying among control Cassin's auklet pairs, but pairs that we induced to relay bred more successfully than naturally late pairs, and similar to values predicted from laying dates of their first eggs. Their chicks also fledged heavier and younger than late control chicks, and similar to values in early control chicks, but followed the population-wide seasonal decline in wing length at fledging. Nestling diets were dominated by Neocalanus copepods until late in the season, a sign that feeding conditions remained favourable until late. In contrast, rhinoceros auklet pairs induced to relay followed the population-wide seasonal decline in breeding success, which was driven by a decline in hatching success. Pacific sandlance Ammodytes hexapterus, thought to be a preferred prey species, virtually disappeared from nestling diets in mid-to-late season, yet there was no seasonal decline in fledging mass. However, chicks from replacement eggs followed the declines among control chicks in both age and wing length at fledging. Despite the female having produced a replacement egg, and despite delayed breeding, there appeared to be little immediate consequence associated with relaying for Cassin's auklets, except for a tendency for their chicks to fledge with short wings. Consequences were more marked in rhinoceros auklets (greatly reduced hatching success, and having their chicks fledge with short wings), and this may have been due to the large investment made in eggs, and/or to delayed breeding. Results of this study show that attributes of Cassin's and rhinoceros auklets that lay at different times in the season can be important in driving seasonal declines in breeding performance, as found in studies on other Alcidae. They also show how decisions taken during the egg stage can have variable yet potentially important implications for fitness, even in relatively long-lived species that lay single-egg clutches.

Yolk carotenoids and stable isotopes reveal links among environment, foraging behavior and seabird breeding success

“…Again, this might indicate that females have little difficulty meeting their physiological requirements for carotenoids in any year, even though rhinoceros auklets lay larger eggs relative to body mass (Hipfner et al 2004). In contrast to Cassin's auklets, however, we did find the predicted positive relationship between the mean total yolk carotenoid concentration and the proportion of females in the population that raised their single offspring to fledging in a given year, especially among the relaying females themselves.…”

“…In a species that consumes large quantities of carotenoid-rich prey, and that lays a relatively small (Hipfner et al 2004), single egg (Biard et al 2006), females may have little difficulty in meeting their physiological requirements for carotenoids. This might be especially true of early-laying females, whose diets can be especially rich in crustaceans (Sorenson et al 2009), and at our study site, which lies within an extremely productive marine system (Ware and Thomson 2005).…”

Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids

“…Prey items: We collected prey items delivered to Cassin's auklet and rhinoceros auklet nestlings at the colony, using standard methods (Hipfner et al 2004). Provisioning Cassin's auklets were intercepted in pheasant nets set up at the base of the breeding colony, removed by hand and induced to regurgitate food loads into plastic bottles.…”

Matches and mismatches: ocean climate, prey phenology and breeding success in a zooplanktivorous seabird

“…Fledging masses did not decline more steeply with later hatching in warmer than in colder years (P4), and there was only a weak tendency for survival to do so (P6). Experiments on several seabird species (Hatchwell 1991, De Forest & Gaston 1996, Daunt et al 1999, including Cassin's auklets (Morbey & Ydenberg 2000, Hipfner et al 2004, indicate that differences in the parental capacities of early and late breeders, rather than seasonal deteriorations in feeding conditions, often drive the ubiquitous seasonal declines in offspring performance. Thus, while the result is not consistent with predictions of the match-mismatch hypothesis, it is difficult to draw firm conclusions about the putative role of feeding conditions without experimenting to control for confounding factors.…”