. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 225 The Silver Gull (Lams novaehollandiae) Gulls were present on the islands in greater numbers by day than by night. Indeed, during much of the night no gulls were present at all and must either have gone to sea or moved to a different island to roost. Alternatively, they may have been disturbed by the researchers before detection and may have flown to another island. Silver Gulls were found to be very sensitive to human disturbance at night during banding activities (M. Jones, personal observations). General
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 225 The Silver Gull (Lams novaehollandiae) Gulls were present on the islands in greater numbers by day than by night. Indeed, during much of the night no gulls were present at all and must either have gone to sea or moved to a different island to roost. Alternatively, they may have been disturbed by the researchers before detection and may have flown to another island. Silver Gulls were found to be very sensitive to human disturbance at night during banding activities (M. Jones, personal observations). Generally, numbers gradually increased during the day and then declined again toward evening (Fig. 5). The gulls were exceptional in consistently having as large a population on Price Cay as on Frigate Cay. On both cays, numbers in winter were lower than in summer, perhaps reflecting differences in their general abundance in the Swains at these times of year. Silver Gulls move among islands and between mainland and islands, tracking temporary food sources (Walker, 1988). They are predators of eggs and small chicks at tern and booby colonies (Walker, 1988) and consequently may have been attracted to these cays by the summer peak of breeding of terns and Brown Boobies (Table 1; Figs. 3, 5-7). PRICE. JANUARY 1987 PRICE, JULY 1987 FRIGATE. JANUARY 1988 FRIGATE. JULY 1991 J o C 2 D Z 0 400 800 1200 1600 2000 2400 TIME (HRS) Figure 5. Numbers of Silver Gulls counted at different times of day and at different seasons on Price Cay and Frigate Gulls were mostly scattered around the beach, singly or in twos and threes. This distribution may have provided them good vantage points from which to view birds returning with fish to feed their chicks (Hulsman, 1976). The exceptions were aggregations of gulls in the vegetated zone in the middle of the afternoon, the hottest. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability
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