Speich and Wahl 



Chapter 30 



Marine Habitat Preferences, Variability in Washington 



Dungeness Spit: six showed decreases and six showed no 

 change. East of Dungeness Spit, four subregions showed 

 increases, one showed a decrease and four showed no change. 

 The Dungeness Spit subregion showed no change in density 

 or projected total of birds. 



A different pattern was observed when spring-summer 

 densities and calculated totals were compared with those of 

 winter in more northern and eastern areas of northern Puget 

 Sound. Within the eastern bays and passages of Whatcom 

 and Skagit counties, the area to the east of Rosario Strait, 

 including Bellingham, Padilla, Samish. Fidalgo and Lummi 

 bays, murrelets were more plentiful during the winter period 

 in five of the seven (71 percent) subregions and there was no 

 change in the other two subregions (29 percent). 



This pattern was also observed in the bays and passages 

 of the San Juan Islands. There, Marbled Murrelet densities 

 and projected totals were greater in 1 1 (52 percent) of the 21 

 subregions of this geographic area. Values decreased in only 

 five subregions (24 percent) and remained the same in five 

 others (24 percent). 



Long-Term Trends in Abundance and Occurrence - 

 Puget Sound 



As reported earlier (Speich and others 1992), there are 

 no data that will allow for the quantification of long term 

 changes in the abundance of Marbled Murrelets in Washington 

 marine waters. Qualitative statements in early accounts suggest 

 that the species was once more abundant than present in 

 Puget Sound waters. 



Long-Term Trends in Abundance and Occurrence - 

 Pacific Ocean Coast 



There are no data that we are aware of that allow a direct 

 appraisal of the long term stabili ty, or instability, of populations 

 along the Pacific Ocean coast of Washington, over the last 

 century, or even over the last several decades. The only 

 quantified information available is the data set collected by 

 Wahl from offshore birding trips ifom Grays Harbor to over 

 the continental shelf break, covering the years 1971 through 

 1993 (table 3, fig. 12). Therein, no long term trend in the 

 abundance of Marbled Murrelets is evident, except that since 

 1989. yearly abundance is visibly diminished. The lowest 

 level of murrelet abundance over the entire study period 

 occurred in 1993. 



We are unable to directly predict if the pattern of 

 abundance observed in nearshore waters near Grays Harbor 

 are indicative of abundance patterns along the entire outer 

 coast of Washington. However, some insight is obtained 

 by considering the yearly patterns of relative abundance of 

 other marine bird species occurring in nearshore and 

 continental shelf waters off of Grays Harbor. Several marine 

 species, consisting of four families of birds, and comprising 

 local breeders, migrants, and winter visitors, were less 

 abundant in recent years in the Grays Harbor study area. 

 Wahl's unpublished observations are summarized below. 

 The lowest abundances since 1971 were recorded during 



the past two years for eight species (Sooty Shearwater 

 [Puffinus griseus], Red-necked Phalarope [Phalaropus 

 lobatus], Sabine's Gull [Xema sabini], Arctic Tem [Sterna 

 paradisaea], Common Murre [Uria aalge], Cassin's Auklet 

 [Ptychoramphus aleuticus], Rhinoceros Auklet, Tufted 

 Puffin [Fratercula cirrhata]).and during one of the last 

 two years for two species (Fork-tailed Storm-Petrel 

 [Oceanodroma furcata], Red Phalarope [Phalaropus 

 fidicarid}). Of interest, Common Murre abundance decreased 

 noticeably in 1989, and has remained low, after several 

 years (1980-1988) of relative high abundance. The 

 abundance pattern of the last species corresponds to that 

 observed for the Marbled Murrelet, relative low abundance 

 since 1989 (fig. 12). 



Discussion 



The overall pattern of abundance (density) and occurrence 

 of Marbled Murrelets observed in the marine habitats of 

 Puget Sound is one of variability. Our impression of Marbled 

 Murrelets in Puget Sound before this limited analysis was of 

 a species that moves about a great deal on several temporal 

 scales: seasons, daily, and hourly. Indeed, we have often 

 observed Marbled Murrelets foraging in a particular area 

 then departing that area in a short period of time, and flying 

 out of our sight to another unknown location. Such movements 

 may account for the generally low probability of encountering 

 murrelets on censuses within habitat types. Thus, the observed 

 occurrence patterns are not surprising. However, there are 

 sources of noise in the original census program that could 

 give a partially false impression of this species' patterns of 

 occurrence. Specifically, not discounting our general 

 impression of variability, we have noticed that they are often 

 found in specific areas, while other areas are less likely to 

 contain them. Thus, since any specific habitat type presented 

 is usually represented by several spatially distinct censuses 

 and the mixing of censuses, some often with and without 

 detecting murrelets, leads to lowered occurrence rates. We 

 predict that this will be the case, and that the habitat spatial 

 scale we presented here for Puget Sound will turn out to be 

 too coarse. 



Our field observations of Marbled Murrelets in Puget 

 Sound, during the course of formal censuses and otherwise, 

 suggest that the foraging distribution is closely linked to 

 tidal patterns, in particular to specific locations when tidal 

 flows are clearly evident. The locations of tidal activity 

 covered by data that are presented here (fig s. 5 and 6) are 

 well known and particularly prominent places of tidal activity. 

 However, tidal activity is observable throughout Puget Sound 

 and is likely the single dominant and persistent physical 

 process there. We suggest that analysis of our data at the 

 level of individual censuses may give insight into the relative 

 importance of tidal activity in determining the movements 

 and foraging areas of Marbled Murrelets. 



As recognized previously, there are seasonal regional 

 patterns in the distribution and abundance of murrelets in 



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



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