. The Canadian field-naturalist. 258 The Canadian Field-Naturalist Vol. 78 100. 2 3^ ^? 5 MAY JUNE 2 3 4 12 3 JULY AUGUST Figure 22. Composition of the Brandt's Cormorant roost on Mandarte Island in the course of the summer (weekly averages). adult Brandt's Cormorant to the Mandarte roost in 1958 (aged by plumage by van Tets). The number using the roost during the winter is indicated by the following counts: 500, January 17, 1959; 800, December 29, 1959. Peak numbers are usually seen only at dusk, with less than 100 birds present by day. Birds in immature plumage can be seen to court and build
. The Canadian field-naturalist. 258 The Canadian Field-Naturalist Vol. 78 100. 2 3^ ^? 5 MAY JUNE 2 3 4 12 3 JULY AUGUST Figure 22. Composition of the Brandt's Cormorant roost on Mandarte Island in the course of the summer (weekly averages). adult Brandt's Cormorant to the Mandarte roost in 1958 (aged by plumage by van Tets). The number using the roost during the winter is indicated by the following counts: 500, January 17, 1959; 800, December 29, 1959. Peak numbers are usually seen only at dusk, with less than 100 birds present by day. Birds in immature plumage can be seen to court and build flimsy nests of grasses and algae throughout June, but up to 1962 no eggs have been laid. Kortlandt (1942) made an intensive study of Dutch colonies of Phalacrocorax carbo, and found that almost all one and two year old birds live in the colonies in May, displaying immature reproductive behaviour and building play nests. He found the species to start breeding at three years, though many individuals first bred at four and five years. Of interest here is that though birds usually bred in the natal colony, they often spent the immature years in other colonies, and Kortlandt gathered suggestive evidence that new colonies originate in three phases. First the cormorants use the site as a sleeping place, next immatures move in during the breeding season and go through play nesting, still returning to the natal colony when mature however, and finally the colony becomes established when birds with previous breeding experience elsewhere settle and begin to nest. We feel that the Mandarte roost of Brandt's Cormorant repre- sents the second phase, namely use of the site as winter roost and occupation by immatures in the breeding season, and consider it likely that a nesting group will be established in the next few Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustra
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