Influences of Larus gulls and nocturnal environmental condition on Leach's storm-petrel activity patterns at the breeding colony

• Main Author: Bryant, Shelley L.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1993
• Subjects: Gull Island; Newfoundland; Green Island
• Online Access: https://research.library.mun.ca/4155/; https://research.library.mun.ca/4155/1/Bryant_ShelleyL.pdf; https://research.library.mun.ca/4155/3/Bryant_ShelleyL.pdf

The risk of predation is perhaps the most serious pressure an animal must contend with during its lifetime. Predation risk has played a strong selective force in many aspects of life history, including the activity patterns of prey species. Leach's Storm-Petrels (Oceanodroma leucothoa) arrive and depart from breeding colonies only at night. Anecdotal reports suggest that storm-petrels return to the colony later on bright nights than on overcast or foggy ones, and that fewer birds are seen at the colony on bright nights. These are considered predator avoidance behaviours as diurnal gulls prey on storm-petrels, especially on bright moonlit nights. -- This study examined the effects of the presence of predators on the activity and parental care patterns at two Leach's Storm-Petrel colonies - one with gulls (Gull Island) and one without (Green Island). Data were collected on storm-petrel flight and vocalization activity, reproductive chronology, chick interfeed interval, and gull activity and predation on Leach's Storm-Petrels. A model gull experiment was conducted on Green Island to determine storm-petrel responsiveness to gulls at this colony. In addition, fledging mass and winglength measurements were collected from five colonies; four in Newfoundland and one in Maine. -- Differences were found in storm-petrel responses to nocturnal environmental condition both between the colonies and between the reproductive phases of incubation and chick rearing. At both colonies, and over the entire reproductive season, storm-petrels arrived and began to vocalize later on bright evenings than on intermediate or dark ones, and under clear versus cloudy or foggy skies. Leach's Storm-Petrels on Gull Island were also quiet on arrival for a longer period than those on Green Island. Once at the colony, the behaviour of the storm-petrels was similar under a variety of nocturnal environmental conditions at Gull and Green Islands, although the storm-petrels at Green Island were apparently less affected by nocturnal environmental ...