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Because many seabirds depend on the inaccessibility of their breeding sites to deter terrestrial predators (Lack 1967), the effects of predator invasion of seabird colonies can be drastic. In this paper, I report visitation by ermine (Mustela erminea) to several Black Guillemot (Cepphus grylle) colonies at a low arctic site, and describe its consequences. I studied the breeding and feeding habits of guillemots during the 1981-1983 nesting seasons at colonies near the juncture of Hudson Bay and Hudson Strait (62023'N, 78*01'W). Islands used for nesting had low relief, and breeding populations ranged from a few to 190 pairs. Most work was done on Pitsulak City, but 11 other nesting islands were also visited. Laying peaked in late June-early July, with the hatching peak following one month later. Gaston et al. (in press) described the biota of the area, and named the islands here mentioned. I saw no ermine in 1981 or 1982, and no sightings were reported from biologists' and Inuit camps on the mainland and on large islands in the area. In 1983, ermine were frequently seen around camps, and invaded several islands where guillemots nested. Table 1 summarizes evidence for ermine visitation of islands. Ermine presence was confirmed on three islands by direct sightings. On three other isla ds, low breeding success and other circumstantial evidence also suggested ermine visitation. On one of these islands (Black), I found plundered eggs inside nest cavities, where they could not have been reached by gulls, and, on Kingituayu, I found three carcasses of adult guillemots

Birds with petroleum-coated plumage may ingest and/or inhale substantial amounts of the substance while preening (Hartung 1963); small amounts of ingested oil have resulted in marked physiological changes in nestling larids (Miller et al. 1978, Butler and Lukasiewicz 1979) and alcids (Peakall et al. 1980). Similar oil-induced physiological aberrations in adult birds may well impair reproductive success. In the present study, we examined the effect of sub-lethal oil ingestion by adult Leach's Storm-Petrels (Oceanodroma leucorhoa) on the survival and growth of their chicks. Leach's Storm-Petrels are small (adult weight 45 g), pelagic-feeding, burrow-nesting procellarids with long incubation (45 days), and chick growth (63-70 days to fledging) periods (Palmer 1962). They are ideal subjects for the study of oil effects on reproduction because: (1) they feed on the surface, where oil slicks are located; (2) their burrow nest provides the chicks with a uniform environment, and allows easy access to both adults and chicks with little disturbance to the rest of the colony; and (3) like all procellarids, they lay only a single egg. Because of their low reproductive potential, members of this order may be particularly vulnerable to the impact of oil contamination. Our study was conducted during the 1979 and 1980 breeding seasons on an island 12 km off the coast of Maine. We located nest burrows while the petrels were incubating eggs, and made a small opening (10 x 10 cm) into each nest chamber for easy access to the birds. A cedar shingle was placed over the hole, covered with the excavated soil, and weighted with a large painted stone. Adult storm-petrels were banded within two days after their chicks hatched. Each burrow was randomly assigned to one of three groups: control burrows, burrows from which one adult was dosed, and burrows from which both adults were dosed. Adults from experimental burrows were given a single 0. 1-ml dose of Prudhoe Bay crude oil (PBCO; chemical analysis in Peakall et al. 1982) by intubation. Adults from control burrows were sham-dosed, i.e., handled and intubated exactly like dosed birds except that nothing was put into the stomach. One-half of all control burrows had both adults sham-dosed while in the remaining control pairs only one adult was so treated. Each treatment group was subdivided into two separate experiments. In the first experiment, adults were dosed while brooding twoto three-day-old chicks (chick body weight 10 ? 1 g). In the second, adults were dosed when their chicks were 10-15 days old (chick body weight 29 + 3 g). Adults brooding young chicks were captured in their burrows during the day; those with older chicks were captured with a trap at night when they returned to feed their offspring. The trap allowed the returning adult to enter the burrow and feed its chick, but prevented it from leaving. Chicks were weighed when adults were dosed and at three-day intervals for 21 days thereafter. A sub-sample of adults was captured and killed at the end of the experiment. Livers, nasal glands, and adrenal glands were removed and weighed. In a final experiment, chicks weighing about 28 g (10-15 days of age) were dosed with 0.05 ml PBCO by intubation. Chicks were weighed at three-day intervals for 21 days, and their growth and survival were compared to those of sham-dosed control chicks. The 0.1-ml dose level used for adults is equivalent to 2.5 ml/kg body weight and is intermediate to doses given to other wild and captive seabirds (0.3-5 ml/kg). Chicks were approximately one-half adult weight when dosed and were therefore given a 0.05-ml dose. Earlier studies on Herring Gulls (Larus argentatus; Miller et al. 1978, Butler and Lukasiewicz 1979) and Black Guillemots (Cepphus grylle; Peakall et al. 1980), used PBCO at this same 2.5 ml/kg dose level. All statistical comparisons, unless otherwise noted were done using ANOVA and Duncan's New Multiple Range Tests. Values appearing in the text are expressed as mean ? standard error with sample sizes in parentheses. All chicks of control adults (n = 16) survived the 21day experimental period. However, in the first experiment (adults brooding twoto three-day-old chicks), chick survival was reduced to 70% when one adult (n = 23) was dosed and to 52% when both adults (n = 21) were dosed (P < 0.01 for both groups using the test for differences in equality of two percentages). All mortality occurred within six days of dosing. The growth rates (g/day) for all chicks surviving to three days indicate that experimental birds gained significantly less weight than controls (mean weight gains were 1.5 ? 0.2 g/day for controls; 0.7 ? 0.2 g/day for chicks with one dosed adult, and 0.5 ? 0.2 g/day for chicks with two dosed adults; P < 0.01 for both groups). When data for chicks surviving to 21 days were considered, the only significant difference was that the growth rate at 6 days was lower (1.0 ? 0.3 g/day compared to a control value of 1.8 ? 0.1 g/day) for the group in which both parents were dosed. The control growth rates were similar to published values (Ricklefs et al. 1980). In the second experiment (adults with chicks 10-15 days

I studied chick growth and parental provisioning behavior of Black Guillemots (Cepphus grylle) in Hudson Bay, Canada. Chicks received benthic blennies, principally Stichaeus punctatus and Eumesogrammus praecisus, which parents caught in water less than 40 m deep close to the colony. Chick feeds were more frequent in the morning but feeding rates did not vary with age of young. Size of prey items increased during the nestling period, and energy intake peaked at about 780 kJ/day/chick when chicks were 25 days of age. Black Guillemots can maintain higher reproductive rates than offshore-feeding Alcidae because their short foraging range and the temporal and spatial predictability of their benthic prey permit higher rates of chick provisioning.