Geology topics

Bay D. Roberts

Publications and source records attributed to Bay D. Roberts.

7 recordsLinked to original sources

USGS2008

Adult survival of Black-legged Kittiwakes Rissa tridactyla in a Pacific colony

Breeding Black-legged Kittiwakes Rissa tridactyla survived at a mean annual rate of 0.926 in four years at a colony in Alaska. Survival rates observed in sexed males (0.930) and females (0.937) did not differ significantly. The rate of return among nonbreeding Kittiwakes (0.839) was lower than that of known breeders, presumably because more nonbreeders moved away from the study plots where they were marked. Individual nonbreeders frequented sites up to 5 km apart on the same island, while a few established breeders moved up to 2.5 km between years. Mate retention in breeding Kittiwakes averaged 69% in three years. Among pairs that split, the cause of changing mates was about equally divided between death (46%) and divorce (54%). Average adult life expectancy was estimated at 13.0 years. Combined with annual productivity averaging 0.17 chick per nest, the observed survival was insufficient for maintaining population size. Rather, an irregular decline observed in the study colony since 1981 is consistent with the model of a closed population with little or no recruitment. Compared to their Atlantic counterparts, Pacific Kittiwakes have low productivity and high survival. The question arises whether differences reflect phenotypic plasticity or genetically determined variation in population parameters.

Alaska↗

USGS1994

Chick movements and adoption in a colony of Black-Legged Kittiwakes

We studied Black-legged Kittiwakes ( Rissa tridactyla ) in an Alaskan colony where movement of young among nests was possible because of moderate terrain and close nest spacing. Thirty-three percent of chicks in a focal group departed their nests prior to fledging, and seven of the vagrant chicks (58%) were adopted by foster parents. The overall frequency of adoption in three years was 8% of 88 chicks from 57 focal nests. Premature nest-departure occurred at different stages among first- and second-hatched chicks. Departing second-hatched chicks were usually expelled by their nest mates within a few days after hatching. First-hatched chicks left at all stages and usually were the sole nest occupant when they departed. The evidence for parent-offspring recognition was equivocal. Adults accepted alien chicks that appeared in the nest and also occasionally attacked their own young outside the nest. However, asymmetry in the response of parents and nonparents to vagrant chicks seeking access to a nest suggested that adults were often able to discriminate appropriately. Vagrant chicks appeared to have little control over their fate-most entered nests where they were smaller than the resident young and suffered nest-mate aggression. Reproductive error seems the likely explanation for the acceptance and foster caregiving observed in adult kittiwakes.

Alaska↗

USGS1993

Behavioral ecology of black-legged kittiwakes during chick rearing in a failing colony

Compared with their Atlantic counterparts, Black-legged Kittiwakes ( Rissa tridactyla ) in North Pacific colonies are notably unproductive. A large colony on Middleton Island, Alaska, has in most years since 1981 seen complete breeding failure and the population has declined by half. We compared parent-offspring behaviors in this colony during two years that differed in overall breeding success. Potential indicators of food stress included parental attendance at the nest, foraging trip lengths, chick feeding and begging rates, and sibling aggression. Whereas chick feeding and begging rates were strongly correlated with overall breeding performance, patterns of time allocation by adults (nest attendance and foraging trips) were not. Contrasts between years and comparisons with data from other colonies in and outside Alaska point to food shortage as the likely cause of recurrent breeding failure on Middleton.

Alaska↗

USGS1990

Colony attendance and population monitoring of Least and Crested auklets on St. Lawrence Island, Alaska

Diurnal and seasonal patterns of attendance of Least Auklets ( Aethia pusilla ) and Crested Auklets ( A. cristatella ) were studied in 1987 at breeding colonies on St. Lawrence Island, Alaska. Numbers of auklets attending eight 200-m 2 plots on talus slopes were counted throughout the day by observers on 11 occasions through the breeding season. Numbers attending smaller plots were recorded on time-lapse film on 71 different days. Another 16 200-m 2 plots were censused for auklets using surface counts. Within-day patterns of attendance were extremely variable over small and large temporal scales. Peaks of attendance occurred in late morning and late evening, with a 7- to 12-hr period of absence in the middle of the day. Attendance varied markedly between days, and numbers were negatively correlated with wind speed and the magnitude of tidal oscillations. Patterns of attendance also varied with stage of breeding, and counts were least variable during incubation and early chick rearing. Whereas Least Auklet numbers peaked during prelaying, Crested Auklet numbers peaked during incubation. Counts indicated that auklets at Kongkok Bay have increased about twofold since studies in the mid-1960s. Recommendations are made for future monitoring of auklet populations.

Alaska↗

USGS1990

Effects of human disturbance on breeding Least and Crested Auklets at St. Lawrence Island, Alaska

We studied breeding success, chick growth, and diets of Least ( Aethia pusilla ) and Crested ( A. cristatella ) auklets on St. Lawrence Island, Alaska, in summer 1987. Least Auklets had higher breeding success on control plots (50-66%) than on disturbed plots (36%). Crested Auklets had a breeding success of 42% on disturbed plots. Predation by microtine rodents and weather accounted for most natural chick mortality. Least Auklet chicks grew at a maximum rate of 4.9 g/day, and Crested Auklet chicks at 12.8 g/day. Least Auklet chicks were fed mostly copepods ( Neocalanus plumchrus ), whereas Crested Auklet chicks were fed Thysanoessa euphausiids.

Alaska↗

USGS1990

Monitoring St. Lawrence Island and Cape Thompson seabird populations

About 1.8 million seabirds of 12 species breed on St. Lawrence Island (Figure 1) - one of the largest aggregations of breeding seabirds in the subarctic Pacific. Colonies of least and crested auklets alone, totaling 1.5 million birds, contain a substantial proportion (perhaps 20%) of these species’ world populations. Large seabird colonies occur also at Cape Thompson (Figure 2), where thick-billed and common murres (ea. 360,000) and black-legged kittiwakes (ea. 26,000) are the numerically dominant species. Although critical nesting and foraging habitats of Cape Thompson and St, Lawrence Island seabirds have so far remained mostly free from disturbance or alteration, there is a possibility of adverse effects on either or both components of the birds’ environment from the exploration, production, or transport of oil and gas in the region.

Conference Paper↗

USGS1988

Populations, productivity, and feeding habits of seabirds on St. Lawrence Island, Alaska: Final report

A field camp was established at Kongkok Bay near the southwest cape of St. Lawrence Island and occupied continuously from 24 May to 2 September 1987. Permanent study plots were selected for both cliff and crevice-nesting species, and regular observations were made throughout the breeding season to document attendance patterns, breeding phenology, and success. Periodic collections of adults offshore and of chick meals in the colonies were used to determine the food habits of study species. Additional plots for population monitoring of murres and kittiwakes were established in colonies near Savoonga on the north side of the island, and counts were made there between 23 July and 1 August. Shore based work was supplemented with offshore studies of seabird foraging distribution from the USFWS vessel TIGLAX between 18 August and 3 September 1987. Populations of all study species in the Kongkok Bay area increased since the last study of seabirds there (murres 20, kittiwakes 87, Least Auklets 8, Crested Auklets 442). Pelagic Cormorants, Common Murres, and Thick-billed Murres exhibited average, or above average, breeding success at Kongkok in 1987. Black-legged Kittiwakes exhibited near-total reproductive failure. Crested and Least Auklets had high levels of breeding success after the effects of observer disturbance were taken into account. Predation by microtine rodents and foxes was a significant source of chick mortality on auklets. Feeding concentrations were found primarily north of Gambell in the Anadyr Strait or western Chirikof Basin. Kittiwakes were dispersed widely over the study area. Diets of all species studied were normal and, with the exception of kittiwakes, there was no evidence of problems in obtaining food. Current methods for assessing population changes in cliff-nesting species are considered adequate, but better techniques are needed for crevice-nesting auklets. Time-lapse photography offers the greatest potential for monitoring auklet numbers. A protocol is suggested for monitoring populations of murres, kittiwakes, and auklets at colonies in the Bering and Chukchi Seas. It calls for annual visits to selected colonies during two stages of the nesting cycle to assess numbers and breeding productivity. The breeding failure of Black-legged Kittiwakes on St. Lawrence Island in 1987 was part of a pervasive syndrome of failure in this species observed throughout the Bering Sea and Gulf of Alaska in recent years. The causes of recurrent, widespread breeding failure need to be identified if kittiwakes are to have a role in area-wide population monitoring during the period of Alaskan development by the oil and gas industry.

Alaska↗