Chapter 3 



Comparative Reproductive Ecology of the Auks 

 (Family Alcidae) with Emphasis on the Marbled Murrelet 



Ton! L. De Santo' : S. Kim Nelson 1 



Abstract: Marbled Murrelets (Brochyramphus marmoratus) are 

 comparable to most alcids with respect to many features of their 

 reproductive ecology. Most of the 22 species of alcids are colonial 

 in their nesting habits, most exhibit breeding site, nest site, and 

 mate fidelity, over half lay one egg clutches, and all share duties 

 of incubation and chick rearing with their mates. Most alcids nest 

 on rocky substrates, in earthen burrows, or in holes in sand, 

 around logs, or roots. Marbled Murrelets are unique in choice of 

 nesting habitat. In the northern part of their range, they nest on 

 rocky substrate; elsewhere, they nest in the upper canopy of coastal 

 coniferous forest trees, sometimes in what appear to be loose 

 aggregations. Marbled Murrelet young are semi-precocial as are 

 most alcids, yet they hatch from relatively large eggs (relative to 

 adult body size) which are nearly as large as those of the precocial 

 murrelets. They also share with precocial murrelets an early age of 

 thermoregulation. as indicated by a short brooding period. Hatching 

 success in monitored Marbled Murrelets nests was somewhat 

 lower and fledging success was markedly lower than for other 

 alcids. The lower rate of reproduction was attributed in part to 

 egg and chick predation. Marbled Murrelet young raised in forest 

 nests may incur additional mortality on their trips from inland 

 nest sites to the ocean. El Nino effects may also decrease produc- 

 tivity in this species. To document murrelet reproduction more 

 fully, further study of individually marked, breeding Marbled 

 Murrelets and their young conducted during periods without El 

 Nino influences is needed. 



The family Alcidae is composed of 22 living species of 

 marine diving birds representing 12 genera (table 1). These 

 birds, commonly referred to as auks, murres, guillemots, 

 murrelets, aukJets. and puffins, inhabit oceans of the Northern 

 Hemisphere (Nettleship and Evans 1985; Udvardy 1963). 

 Although seabird research is logistically difficult, much 

 information has been gathered on the reproductive biology 

 of alcids. Such research has been facilitated by the colonial 

 nature of most species and by the accessibility of some 

 breeding areas to scientists (Birkhead 1985). Thorough 

 reviews have been published on nearly half of the species. 

 For instance. Birkhead (1985), Gaston (1985), Harris and 

 Birkhead (1985). Hudson (1985), and Nettleship and Evans 

 (1985) present reviews of the reproductive biology of Atlantic 

 alcids (Dovekie, Razorbill, Common Murre, Thick-billed 

 Murre. Black Guillemot, Atlantic Puffin, and the extinct 

 Great Auk [Plautus impennis]). Reviews of four auks that 



1 Research Wildlife Biologists. Oregon Cooperative Wildlife Research 

 Unit. Oregon State University. Nash 104, Corvallis. OR 97331-3803 



: Current address: Postdoctoral Research Associate, Pacific Northwest 

 Research Station. USDA Forest Service. 2770 Sherwood Lane, Suite 2A, 

 Juneau. AK 99801-8545 



breed on the Farallon Islands in the Pacific Ocean (Common 

 Murre, Pigeon Guillemot, Cassin's Auklet, Rhinoceros Auklet, 

 and Tufted Puffin) are presented by Ainley (1990), Ainley 

 and others (1990a, b, c) and Boekelheide and others (1990). 

 Four inshore fish feeding alcids of the northern Pacific Ocean 

 (Kittlitz's Murrelet, Pigeon Guillemot, Spectacled Guillemot, 

 and Marbled Murrelet) are reviewed by Ewins and others 

 (1993) (also see Marshall 1988a for a review of the Marbled 

 Murrelet). The Ancient Murrelet, another inhabitant of the 

 northern Pacific Ocean, has been reviewed by Gaston (1992). 



Alcids that nest in small, loosely-aggregated colonies, as 

 isolated pairs, or in areas less accessible to researchers, have 

 not been well studied. For instance, the reproductive biology 

 of Craven's and Kittlitz's murrelets and Spectacled Guillemots 

 is largely unknown. Although Marbled Murrelets have received 

 considerable attention during the last two decades, the 

 reproductive ecology of this species is not well understood. 

 Unlike many other alcids, Marbled Murrelets do not nest in 

 conspicuous colonies on cliffs, in rock crevices, or in burrows 

 in the ground. Instead, this species nests on the alpine tundra 

 or in the upper canopy of old-growth coniferous trees (Hamer 

 and Nelson, this volume b; Marshall 1988a). Additionally, 

 Marbled Murrelets are secretive around their nests and active 

 during low light periods at dawn and dusk. Consequently, 

 few nests have been located and observed, and few quantitative 

 data have been collected. 



This paper summarizes the reproductive ecology of the 

 auk family and specifically compares Marbled Murrelets to 

 the other alcids. Such a comparison may allow for a better 

 understanding of the reproductive strategy of Marbled 

 Murrelets and should provide useful information for 

 conservation and management of this species. 



Nest Sites and Coloniality 



The nest sites of all alcids have been described, although 

 few nests of some species have been located (e.g., Kittlitz's 

 and Marbled murrelets). Murres and Razorbills nest primarily 

 on cliff ledges or in crevices or caves. The nests of Common 

 and Thick-billed murres are in the open whereas those of 

 Razorbills are typically partially or fully enclosed (Byrd and 

 others 1993; Harris and Birkhead 1985). Puffins and 

 Rhinoceros Auklets nest in burrows they excavate. Addition- 

 ally, nests of these species are found in rock crevices (Tufted 

 and Homed, on the level ground of forested islands (Rhinoceros 

 Auklet), and among boulders and rocks of islands lacking 

 soft substrate for burrowing (Atlantic Puffin) (Byrd and 

 others 1993; Hatch and Hatch 1983). The guillemots nest in 

 cracks and crevices of cliffs, among stones or boulders, in 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



33 



