Sex differences in reproductive effort and the potential for a mixed reproductive strategy in the Atlantic puffin (Fratercula arctica)

Creelman, Elizabeth (1987) Sex differences in reproductive effort and the potential for a mixed reproductive strategy in the Atlantic puffin (Fratercula arctica). Masters thesis, Memorial University of Newfoundland.

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Abstract

Atlantic Puffins (Fratercula arctica) on Gull Island, Newfoundland were studied in order to compare the sexes in their patterns of parental activities during the breeding season. Time allocation was categorized as on the slope, in the burrow, and away from the colony. Compared to males, females spent more time in the burrow during pre-laying and incubation, and more time away during the chick-rearing period. With the exception of pre-laying, males spent more time on the slope throughout the season than females. Males were involved in a greater number of burrow maintenance activities and aggressive interactions than females, but because males spent more time on the slope, there were no differences in the rates of these activities. Females delivered more fish meals to chicks per season than did males. No sex differences occurred in the number, size or species of fish per meal, suggesting that the longer absence by females may have been due to greater time spent foraging for chick meals. Male and female Atlantic Puffins both perform all of the breeding activities to some extent, and probably contribute similar amounts of time and energy to reproductive effort. Although females may contribute more towards short-term breeding effort by investing more in current young, males may contribute more towards long-term breeding effort by investing slightly more in activities which serve burrow defense functions. -- This study also attempted to determine whether extra-pair copulations and mate-guarding are important components of the Atlantic Puffins' reproductive strategy. Males apparently attempted to secure extra-pair copulations, as 39% of those observed on the water during the pre-laying stage solicited more than one female. Some of these males may have been mated as males spent more time away from mates during pre-laying and the early part of incubation, but this difference decreased as the number of females yet to lay eggs decreased. Female time away did not show this pattern. Evidence of mate-guarding by males includes observations that mates spent more time paired, and were involved in a greater number of synchronous arrivals and departures, during the pre-laying stage than after. However, greater time paired indicates only greater mate proximity; it does not indicate whether one sex was more responsible than the other for maintaining proximity. In addition, there was no difference in which sex departed or arrived first when pairs arrived and departed together. Because successful copulations appeared to involve only paired birds, females may provide confidence of paternity by rejecting the solicitations of other males.

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