Nelson and Hamer 



Chapters 



Nest Success and Effects of Predation 



Table 1 continued 



1 ?Predation = predation known or suspected based on available evidence. 



2 ?Predator = suspected predator, species seen in vicinity of nest 



3 Common Raven flushed adult off one of these nests; this may have had an impact on its abandonment which occurred 2 days later. 

 > Quintan and Hughes, 1990 



b Naslund and others, in press 



c Twelve Mile Ann nest Brown, pets. comm. 



d Unusual ground level nest located on tree roots above 1 1 m cliff in Log Jam Creek; Brown, pers. comm. 



* Manley and Kelson, in press 

 f Jordan and Hughes, in press 



* Hughes, pers. comm. 

 h P. Jones, pers. comm. 



1 Hamer. unpublished data 



J Ritchie, pers. comm. 



k Nelson, unpublished data; Nelson and Peck, in press 



1 Nelson, unpublished data 



Binford and others 1975. 



Singer and others 1991. 



Singer and others, in press. 

 p Kerns, pers. comm. 



nest from the trunk, limb dia icter at the nest, and nest 

 substrate type (i.e., moss or diff). Edges were defined as 

 unnatural openings, including, but not limited to, roads and 

 clearcuts. Differences in the mean characteristics (ranks) 

 were considered significant at P < 0.05. 



Results and Discussion 



Nest Success and Failure 



Nesting success or failure was documented at 49 percent 

 (32 of 65) of the nests (table 2). Timing of discovery (after 

 the nesting season), limited evidence, or inadequate monitoring 

 prevented conclusions about the outcomes at the remainder of 

 nests. Therefore we limit our discussion to these 32 tree nests. 



Seventy-two percent (23 of 32) of the nests were 

 unsuccessful (tables 1 and 2). Known causes of nest failure 

 included predation of eggs and chicks, nest abandonment 

 by adults, chicks falling from nests, and nestlings dying 

 (tables 1 and 3). Nesting success of 28 percent is lower than 

 reported for 1 7 other alcid species ( x = 57 percent, range = 

 33-86) (De Santo and Nelson, this volume), and for 11 

 species of sub-canopy and canopy nesting neotropical 

 landbird migrants ( x = 5 1 percent, range = 20-77) (Martin 

 1992). However, some species of seabirds (e.g., Xantus' 

 Murrelet [Synthliboramphus hypoleucus]) and forest nesting 

 neotropical migrants (e.g., Western Kingbird [Tyrannus 

 verticalis]), also experienced low nesting success (33 and 

 20 percent, respectively) in some years (Martin 1992; Murray 

 and others 1983). Hatching and fledging success of Marbled 

 Murrelet nests were 67 and 45 percent, respectively. Fledging 

 success was also lower than reported for all other alcid 

 species ( x = 78 percent, range = 66-100, n = 16) (De Santo 

 and Nelson, this volume). 



For all nests, 52 percent of the failures occurred during 

 the egg stage, whereas in Washington, Oregon, and California 



most (62 percent) failed during the chick stage (table 3). The 

 difference in stage of failure between the southern portion of 

 the murrelet' s range and all known nests can be explained by 

 greater abandonment of eggs at nests in Alaska (Naslund, 

 pers. comm.). The high incidence of abandonment in eggs in 

 Alaska between 1991 and 1994 may have been related to 

 limited food resources (Kuletz, pers. comm.). 



Failure during the egg stage was caused by abandonment 

 and predation. Failure during the chick stage occurred because 

 of predation, death from a burst aorta (Palco nest in California), 

 and falling from the nest. Chicks may fall from nests because 

 nests are located on small platforms, or in response to 

 unfavorable weather conditions, such as high winds, or other 

 natural and unnatural disturbances. In Oregon, a 6-day-old 

 chick may have fallen from its ridgetop nest tree (Five 

 Rivers) because of gusty winds that occurred during a midday 

 storm. Chicks are also occasionally very active on the nest, 

 picking at nesting material, changing positions, snapping at 

 insects, exercising their wings, and pacing on the nest limb 

 (see Nelson and Hamer, this volume a). They could easily 

 fall from the nest platform during these times of activity. In 

 addition, predator activity could cause chicks to fall from the 

 nesting platform. 



In addition to failure documented at active nests, nestlings. 

 fledglings, and eggs have been found on the ground during 

 the breeding season at numerous sites throughout North 

 America (table 4). Chicks and eggs located on the ground 

 probably fell from nests as indicated above. However, eggs 

 could also be carried by predators and dropped in locations 

 distant from nest sites. 



Fledglings have been discovered on the ground at varying 

 distances from the ocean during the breeding season (up to 

 101 km inland). Many of these birds still retained an egg 

 tooth and small traces of down on their head and back, 

 indicating recent fledging. Marbled Murrelet hatch-year birds 



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



91 



