Breeding Phenology and Clutch Size in the Marbled Murrelet

Abstract

THE Marbled Murrelet (Brachyramphus marmoratus) is the only species of bird considered to breed regularly in North America whose nest has not been found on this continent, despite recent publicity (Audubon Field Notes 1970). During a study of the feeding and breeding ecology of the Marbled and Ancient (Synthliboramphus antiquus) Murrelets (Sealy 1972) on and in the vicinity of Langara Island, Queen Charlotte Islands, British Columbia (Figure 1), I made observations and obtained information from collected specimens of Marbled Murrelets that indicate its clutch size and the pattern and timing of its breeding cycle there. Although I did not locate any Marbled Murrelet nests, the information contributes to our knowledge of its biology and provides dates between which certain events of its breeding cycle occur in that area. Such information may aid other workers in the ultimate discovery of its nest. A detailed account of the breeding biology of the Marbled and Ancient Murrelets is to be presented elsewhere (Sealy 1972, MS). Several accounts of the many unsuccessful attempts to find the Marbled Murrelet's nest and speculations regarding its location are available (e.g. Young 1930; Guiguet 1950, 1956; Gabrielson and Lincoln 1959; Drent and Guiguet 1961). I do not intend to repeat all these observations but will utilize those from the Queen Charlotte Islands and those of particular interest. The Marbled Murrelet has a disjunct distribution. Its range shows a gap bracing the Aleutian chain with subspecific differences on either side of this gap-B. m. marmoratum of the Northeastern Pacific coast, the race studied here, and B. m. perdix of the Northwestern Pacific coast (see Dement'ev and Gladkov 1951: 245-248; Udvardy 1963: 99).