Egg Mass, Position in the Laying Sequence, and Brood Size in Relation to Canada Goose Reproductive Success

-TO better understand the effects of egg mass and position in the laying sequence on reproductive success of Canada Geese (Brunta canadensis), I determined the fate of eggs, marked embryos near hatching, and recaptured goslings near fledging. Hatching success did not correlate with egg mass and position in the laying sequence. The probability of recapturing marked goslings near fledging was not associated with relative egg mass or position in the laying sequence. These results suggest that egg mass and position in the laying sequence have no short-term implications for the fitness of the chick produced. A reduced survival rate of goslings in larger broods in one year suggests that brood size could be a factor limiting clutch size in Canada Geese. Received 17 Mar. 1986, accepted 16 Mar. 1987. Hatching and fledging success in Anserinae can be reduced by extrinsic (environmental) factors such as predation (Vermeer 1970, Cooper 1978), climate (Cooper 1978), and intraspecific competition (Ewaschuk and Boag 1972). Intrinsic factors such as egg size, egg quality, and position in the laying sequence have been shown to correlate with hatching and fledging success in some nidicolous species (Parsons 1970, Murton et al. 1974, Howe 1976, O’ Connor 1979, Rofstad and Sandvik 1985) but in contrast, little is known regarding these factors for nidifugous species. Brood size also influences fledging success in some nidifugous species (Safriel 1975, Andersson and Eriksson 1982), but not in others (Heusmann 1972, Glasgow 1977, Clawson et al. 1979, Rohwer 1985). Here, I examine the effects of egg size and position in the laying sequence on hatching and fledging success of Canada Geese (Branta canadensis). I address the following questions: (1) Are hatching and fledging success related to egg mass at laying and position in the laying sequence? (2) Does brood size at hatching correlate with brood size near fledging? STUDY AREA AND METHODS The study was carried out in 1983 and 1984 near Brooks, Alberta (50”35’N, 111’54’W). From late March to early May each year, I searched for nests daily at Gleddie Lake. In six other reservoirs nearby, I searched for nests every 2 to 4 days. Nearly all nests had 1 or 2 eggs when found, although some had 3. When more than 1 egg was found in a nest, the degree of staining of eggs was used to assess the order of laying (Cooper 1978). Subsequent I Dept. Zoology, Univ. Alberta, Edmonton, Alberta T6G 2E9, Canada. (Present address: 447, Rang 8, Saint-Sylvkre, Quebec GOZ 1 HO, Canada.)