. Die kanadische Feld - naturforscher. 1980 Notizen 183 in Abbildung 1 dargestellt. Die nördlichste Siedlung gefunden wurde, in der Nähe von einem namenlosen See bei 54° 12' N. Die nördliche Grenze der gemeldeten Zucht Bereich der Great Blue Heron in Saskatchewan und Manitoba deckt sich in etwa mit dem südlichen Rand der Cana- dian Schild. Ein paar kleine Reiher Kolonien haben von der Schutzabdeckung Bereiche, z.b. berichtet, Talbot Lago (54° 07' N, 99° 53' W) und vielen Buchten See (52°40'N, 97°00'W) Manitoba (Vermeer 1973). Die Kolonien wurden deutlich nördlich der Zucht von Godfrey gegeben (1966), in der alle 14 Kolonien in unserem Gestüt wurden

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. The Canadian field-naturalist. 1980 Notes 183 shown in Figure 1. The most northerly colony found was near an unnamed lake at 54° 12'N. The northern limit of the reported breeding range of the Great Blue Heron in Saskatchewan and Manitoba coincides approximately with the southern edge of the Cana- dian Shield. A few small heron colonies have been reported from Shield areas, e.g., Talbot Lake (54°07'N, 99°53'W) and Many Bays Lake (52°40'N, 97°00'W), Manitoba (Vermeer 1973). Those colonies were considerably north of the breeding range given by Godfrey (1966), as were all 14 colonies in our study area. Great Blue Herons have also been observed on Charlton Island, James Bay (H.G. Lumsden, Ontario Ministry of Natural Resources, personal communica- tion). It seems possible that the breeding range extends across Ontario to the northern limits of the boreal forest. Habitat and Nest-site Selection Eight of the 14 colonies were on lake islands (Table 1). All but two colonies were at the water's edge. The herons nested in Jack Pine {Pinus banksiana) or in Black Spruce {Picea mariana) — White Birch {Betula papyrifera) associations. Two colonies were entirely in living Jack Pine with the remaining nine situated in mixtures of dead, dying, and living trees (Table 2). The colonies entirely in living Jack Pine were small (well below the average colony size in this area), sug- gesting that they were newly established and had not yet progressed to a point where heron guano had begun to kill the trees. Miller (1944) hypothesized that an adequate food supply and suitable nesting habitat are the two prime. Figure 1. Map of northwestern Ontario, illustrating the location of new-found Great Blue Heron colonies. The stippled area represents the previously described breeding range, after Godfrey (1966). Table 1—Location and habitat type of active Great Blue Heron colonies observed in northwestern Ontario, 1978 Location of colony Primary nest- tree species No. of nests No. of succe

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