Seasonal changes of the at‐sea distribution and food provisioning in rhinoceros auklets

Abstract

Central-place foraging seabirds increase foodloads and decrease meal frequency when they forage in areas that are distant from the breeding colony. In 2001-2002, we studied the seasonal changes in at-sea distribution, food-load mass, meal frequency, and fledging mass in rhinoceros auklets (Cerorhinca monocerata), which forage in coastal waters during the day and feed their chicks at night. In both years, greater numbers of auklets were observed flying in northern waters that are more distant from the colony in June (65 km) and July (65-66 km) than in May (38-47 km). In July of both years, many auklets flew northward across the transect set 65-120 km north of the colony at sunrise; the birds returned south again at sunset, indicating that they foraged in waters outside the study area. This seasonal northward movement of the foraging area may reflect the migration of their main prey item, the Japanese anchovy (Engraulis japonicus), which move with the Tsushima Warm Current flowing from the southern Sea of Japan. Food-load mass did not increase seasonally. In both years, the estimated daily meal frequency was lower in July than in May or June, partly because of the increased foraging distance in July. Late-hatched chicks also displayed lighter fledging masses than early chicks in both years. We suggest that late breeders are required to forage at great distances for longer periods, which may result in decreased meal frequency and lighter fledging mass of their chicks.

Individual foraging location, but not dietary, specialization: implications for rhinoceros auklets as samplers of forage fish

“…Auklets travelled farther from the colony than previous observations (Cody 1973, Deguchi et al 2010, but were within the maximum foraging range estimated for this species (Kato et al 2003). Maximum foraging distance for Middleton birds was roughly twice the distance for auklets at the Farallon Islands, California (~27 km; Wilkinson et al 2018).…”

Foraging strategy of the little auk Alle alle throughout breeding season – switch from unimodal to bimodal pattern

“…Indeed, empirical data show some seabirds during the incubation period perform longer foraging trips in both duration and distance [chinstrap penguin Pygoscelis antarctica , king penguin Aptenodytes patagonicus , wandering albatross Diomedea exulans , Brűnnich's guillemot Uria lomvia (Charrassin et al , Benvenuti et al , Shaffer et al , Ichii et al , Ito et al )], dive shallower [king penguin, black‐vented shearwater Puffinus opisthomelas , Brűnnich's guillemot (Charrassin et al , Keitt et al , Benvenuti et al , Ito et al )] or forage more efficiently [wandering albatross (Shaffer et al )] compared to the chick‐rearing period. However, duration and destination of foraging trips may vary in relation to location as well as inter‐ and intra‐seasonal fluctuations in the availability of prey (Deguchi et al ), Thus, the extent to which seabirds adjust their foraging tactics during the transition from incubation to provisioning a chick is not fully understood.…”

Flexibility of foraging strategies of the great skua Stercorarius skua breeding in the largest colony in the Barents Sea region

“…The changing degree of central-place constraint in successive phases of the breeding and seasonal changes in prey availability may affect distribution, activity patterns or diet of seabirds [ 4 , 15 , 16 ]. Foraging strategies may also vary within a single breeding season as a response to fluctuations in prey availability that is driven by prey biology, environmental conditions and/or prey depletion near the colony due to intense foraging (“Storer-Ashmole’s halo” [ 17 – 20 ]). Moreover, some species (albatrosses, petrels, little auk Alle alle ) adopt an unimodal foraging strategy during incubation (trip of similar duration) and bimodal strategy during chick-rearing, alternating short trips to nearby locations to collect food for chicks, and long trips to further location mainly for self-feeding (e.g.…”