Speich and Wahl 



Chapter 30 



Marine Habitat Preferences, Variability in Washington 



Puget Sound. Of particular note, are the nearshore subregions 

 along western portion of the Strait of Juan de Fuca where 

 they are found less often during the winter period. This area, 

 particular in Puget Sound, is exposed to winter storm activity, 

 as it opens directly to the Pacific Ocean, while those Strait of 

 Juan de Fuca subregions to the east of Dungeness Spit are 

 relatively protected from western approaching winter storms. 

 The densities in these subregions also suggest a shift of birds 

 from the Strait of Juan de Fuca during the spring and summer 

 periods, to areas in the San Juan Islands and the eastern bays 

 during the fall and winter periods. In addition, as demonstrated 

 in Speich and others (1992), there is apparently an additional 

 influx of Marbled Murrelets into the latter areas from the 

 north, presumably British Columbia. A shift in Marbled 

 Murrelets from the Strait of Juan de Fuca alone cannot 

 account for the increases in numbers in these areas. Similar 

 patterns, though on a lesser scale, are likely present in other 

 areas of Puget Sound. 



An estimate of the size of the Marbled Murrelet population 

 found in the marine waters of Washington during the spring- 

 summer breeding period has been made by Speich and others 

 (1992), calculated at approximately 5,000 birds. Estimates 

 were made for each of four marine regions: southern outer 

 coast. <500 birds; northern outer coast, 1 ,900; southern Puget 

 Sound, 480; and northern Puget Sound, 2, 100. Except for the 

 southern outer coast figure, in reality an educated guess, 

 estimates of breeding populations were based on data from 

 censuses that sampled specific areas, calculated projected 

 numbers for sub-regions (see Wahl and others 1981), then 

 adjusted for the proportions of non-breeding birds and those 

 not present on the water during censuses but incubating and 

 brooding at inland nest sites (Speich and others 1992). We 

 consider these only approximations of the numbers of breeding 

 Marbled Murrelets, requiring a better defined baseline for 

 detecting and appraising potential changes in the future. 



There may be several factors that could explain the 

 observed apparent decrease in rnurrelet abundance in the 

 Grays Harbor study area in the nearshore continental shelf 

 waters. Some may suggest that the population has been 

 reduced by the accumulative removal of terrestrial nesting 

 habitat areas. Such action has the potential to affect Marbled 

 Murrelet populations and may have in particular locations. 

 However, such an evaluation is beyond this paper (see Ralph 

 1994). In our paper, in the time period presented (1971- 

 1993), there are recent indications of changes in the marine 

 carrying capacity of waters over the continental shelf and 

 slope, off Grays Harbor and beyond. This is reflected in the 

 recent record low abundances reported for several species of 

 marine birds, birds representing several different foraging 

 techniques and positions in marine food changes, and of 

 various geographic affinity. On a slightly larger scale, the 

 reduced abundance of Common Murres in the study areas 

 since 1989 suggests that marine food chains have been 

 reduced, or have otherwise become unavailable to Common 

 Murres for several years, because breeding colonies as far 

 south as Oregon have experienced depressed reproduction 



rates (Varoujean, pers. comm.). The study area numbers in 

 part reflect the abundance of murres moving north from 

 Oregon breeding colonies after the breeding period. 

 Additionally, the Common Murre breeding population in 

 Washington has declined over the past decade (Ainley and 

 others 1994; Wilson 1991). Although the Marbled Murrelet 

 is not as oceanic a species as other species reported on here, 

 the documented declines in abundance and local breeding 

 success suggest that fundamental changes in marine systems 

 have occurred, likely expressed by the reduced availability 

 of prey. Considering the temporal and geographic scale of 

 reported effects it is perhaps not surprising that Marbled 

 Murrelet abundance in the Grays Harbor study area was 

 lower the past two years in particular, or even for the past 

 several years. 



The patterns of abundance and occurrence presented 

 herein are descriptive in nature, and represent the "what" 

 stage of the continuing investigation of the Marbled Murrelet 

 in the marine waters of Washington, in this case, Puget 

 Sound. There is certainly the need to advance our 

 understanding of the marine biology of the Marbled Murrelet 

 beyond the descriptive phases of investigation. We need to 

 address, as we have started to do here, "why" Marbled 

 Murrelets are found distributed as they are. However, such 

 post priori explanations are limited by their nature in their 

 potential to allow understanding of the causes of Marbled 

 Murrelet distribution and abundance patterns. Clearly, the 

 development and testing of a priori questions, hypotheses, 

 and the development of models are appropriate and necessary 

 steps for meaningful advancement of our understanding of 

 Marbled Murrelet biology. However, as necessary and 

 desirable as these last steps are, a sound and basic knowledge 

 of the natural history of the species is necessary for the 

 interpretation and evaluation of study and test results and for 

 our understanding of the factors influencing and controlling 

 Marbled Murrelets (see interesting discussion in Oreskes 

 and others [1994]). 



Puget Sound is by its very nature a complex system of 

 bays, estuaries, channels, passages and straits, greatly 

 influenced by tidal and wind patterns, by the influx of fresh 

 water and nutrients from several river systems, and by its 

 connections to the Pacific Ocean. Perhaps a better 

 understanding of, and precision in predicting, the temporal 

 and spatial variable distribution and abundance of the Marbled 

 Murrelet in Puget Sound and along the Pacific Ocean coast 

 would result from an increased understanding of marine 

 physical and biological processes and how they link with 

 Marbled Murrelets. 



Acknowledgments 



This paper is the result of combining the data from 

 several different projects. Consequently, the list of persons 

 and organizations who contributed in many different ways is 

 long. Specific acknowledgments are found in documents 

 cited herein as are the many sources of support (see also 



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



325 



