Varoujean and Williams 



Chapter 31 



Abundance and Distribution in Oregon and Washington 



Table 5 Diving data for radiotagged Marbled Murrelets tracked during the 1988 field 

 season in Oregon, and the 1991 field season in northern California (Varoujean and others 

 1989; Varoujean, unpubl data). 



Mean (s.e.) duration of dive episode: 



X D = 0.30 hours ( 0.04), n = 13 days 



Mean ( s.e.) percentage of time during dive episode spent submerged below the surface: 

 Xj = 67.6 percent ( 1 .0 pet), n = 20 dive episodes 



Percent time spent diving during daylight hours: 



Dive episodes occur 6 times/day from 0530-2130 h (16 h period): 



6 (Xp) = 1.80 h ( 0.24), which is 1 1 .3 percent ( 1.5) of a 16 h day, or a range 



with + 2 s.e. of 8.3-14.3 percent 



Percent time spent actually below the surface during daylight hours: 



Ranges from (Xj - 2 i.e.K8.3 pet) to (Xj + 2 j.<r.X14.3 pet), or 5.4 to 9.9 percent 



Table 6 Number (and percent) of Marbled Murrelets seen as singles, birds in pain and in 

 groups of >2 birds for birds in alternate, and black and white plumage. Data includes att 

 sightings made during aerial surveys of the Oregon coast over the period 22-23 August 1993 



'Groups ranged in size from 3-12 birds (alternate), and 3-5 birds (black/white) 



Table 7 Number (and percent) of Marbled Murrelets seen as singles, birds in pairs and in 

 groups of>2 birds for birds in alternate, and black and white plumage. Data includes all 

 sightings made during aerial surveys of the outer coast of Washington, and the western 

 Strait of Juan de Fuca over the period 4-6 September 1993. 



Groups ranged in size from 3-18 birds (alternate), and 3-4 birds (black/white) 



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



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