Common Murre Uria aalge Scientific name definitions
Version: 2.0 — Published August 6, 2021
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Conservation and Management
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Considered by the International Union for the Conservation of Nature (IUCN) as a species of Least Concern, a classification consistent with the Common Murre’s abundance and wide distribution in the Arctic and Subarctic (detailed in Population Status). IUCN also considered species to be increasing, which on a global scale is debatable (see Population Status: Trends). Protected under Migratory Birds Convention Act of 1917 between Canada, United States, and eventually Mexico; and Wildlife Act (in Canada) as well as many other U.S. federal and state statutes. That convention was amended in 1976 to include the Convention of Migratory Birds and their Environment with the Union of Soviet Socialist Republic. In the Northeast Atlantic region, protected since 1869 by the Protection of Birds at Sea Act. In 1979 the European Union protected murres through passage of the Council Directive 79/409/EEC on the conservation of wild birds, with subsequent updates; and in 1992 passed Council Directive 92/43/EEC on the conservation of natural habitats of wild fauna and flora. The species is considered of importance in the United Kingdom owing to >20% of European population breeding in the region (532). It is not considered a species of concern in the Baltic and Scandinavian regions (533).
Effects of Human Activity
Habitat Loss and Degradation
Habitat Alteration and Disturbance
Sensitive to human intrusion. Panic flights from colonies generated by: low-flying aircraft, especially helicopters (<1,000 m), or close approach (<200 m) by humans on land or in boats and even kayaks (535, 536). Total collapse of colonies in southern Norway caused by increased approach of pleasure boats (537). Researchers, by flushing adults from ledges, can also adversely affect reproductive performance if their activities are not executed with extreme care (364, 538).
Murres are subject to increased levels of mammalian (e.g., S. Wilhelm and G. Robertson, ECCC-CWS) and avian (e.g., 351) predation and at some point relevant agencies may have to discuss whether to attempt to decrease the numbers of predators.
Changes in prey base due to direct human harvesting and indirect changes due to increased ocean temperatures are also likely to increasingly affect prey availability during breeding and throughout the rest of the year. Capelin stocks in the northwest Atlantic have generally decreased and the timing of inshore spawning has become more variable. These changes have affected the growth and survival of murre chicks and have impacted parental foraging effort, mass, and physiology (181, 420, 279, 234).
Indirect Effects of Commercial Fisheries
High metabolic costs require a significant daily ration of coastal fish (see Diet and Foraging: Nutrition and Energetics, and Metabolism), which places murres in direct conflict with commercial fisheries. Extent of conflict intensifies when large murre populations forage in areas of high commercial catch (539). Examples of conflict: Alaska ‒ two murre species, plus kittiwakes (Rissa), on Pribilof Islands and St. Matthew-Hall islands, respectively, consume 5,000 and 2,000 tons of pollock (target for one of world's largest fisheries) during summer (540). Common Murre consumption of Pacific herring (Clupea pallasii) in Prince William Sound may inhibit recruitment of juveniles into the commercial stock (231). Other important prey are also commercial species (Appendices 10, 11, 12). In Shetland Islands, Scotland, year-round population of 168,000 murres during 1981–1983 consumed 14,400 tons of sandlance, or 32% of commercial take (541, 542). In Barents Sea, 2.05 million adult murres (and 340,000 chicks) during 1950s (present only 120 d), consumed 74.9 million tons fish, or 13% of commercial take in 1950s, 7% in 1970s (references in 543). A decrease in availability of capelin, owing to overfishing, has resulted in a steep murre population decrease in the Barents Sea (107). In Prince William Sound, murres take up to 80% of the herring consumed by seabirds during winter (about 6% of herring stock; 231); among Gulf Islands, British Columbia, during winter, 4,000 murres consumed >1,000 kg herring/d; with 3 other species, annually took 14% of herring stock (544). In Oregon, year-round population of about 103,000 murres (with 34,500 fledged chicks), in early 1970s, was estimated to have consumed 21,142 metric tons of prey/yr, 19,872 tons of which was fish, equaling 22% of annual fish production (272). However, Oregon breeding population size likely closer to 350,000 pairs (101), so above estimate is low. In California, murre populations decreased, or failed to recover from oil spills and gill netting, when commercial fishing depleted rockfish (prime breeding season prey), but began to increase with closure of those fisheries and recovery of the rockfish (82, 249). At low population levels, they consumed 8,500 t of forage fish during the breeding season, but with greater than two orders of magnitude increase in their population, murres now consume >60,000 t during the breeding season (83). Common Murre is among the top five seabird consumers of forage fish in the Barents Sea, at 33,000 t per annum, as well as being major consumers in the Norwegian Sea, though orders of magnitude less abundant (274).
Impacts of fish exploitation on murre populations potentially important (on basis of models), but difficult to assess (as above). Major potential for conflicts in Bering Sea, owing to huge fishery for Alaska pollock (Gadus chalcogrammus), a principal murre prey item as juveniles, but system large, with no long-term directed effort of data collection in place (on ecosystem processes), and dramatic climate change obscures the picture (540, 545, 251; see Priorities for Future Research). Over short term, breeding success, chick growth rates, and colony attendance all affected directly by prey abundance (see Demography and Populations: Measures of Breeding Activity). Best example of long-term population change from North Sea, a closed system in which fishery catch-toll and murre populations and biology monitored for decades (see above). Originally, murres (and other seabirds) and predatory fish competed for prey. Excessive exploitation of predatory fishes by 1950s allowed seabird populations to increase; when commercial fisheries then exploited forage fishes, murre (and other seabird) populations declined (494, 546, 547, 548, 549, 109). Over the longer term of the previous century, however, murres have proved to be resilient to altered prey availability (104).
On the Isle of May, Scotland (as detailed in 174, 175, 550, M. P. Harris and S. Wanless, personal communication), one of the best studied murre-prey scenarios, downward trends in breeding success have been synchronized in Common Murre, Razorbill (Alca torda), Atlantic Puffin (Fratercula arctica), Black-legged Kittiwake (Rissa tridactyla), and European Shag (Phalacrocorax aristotelis). However, there has been considerable unexplained annual variation highlighting that different species are impacted differently by environmental conditions. In the case of murres, no evidence that the local sandlance (Ammodytes marinus) fishery had a significant effect on breeding success. Thus, in contrast to kittiwakes, the closure of areas to commercial sandlance fishery along the east coast of Britain did not have a beneficial effect on murre breeding success. Rather it seemed that breeding success became lower in years when thermal conditions for a key prey species of forage fish, Calanus finmarchicus, were unfavorable. Murre breeding success was also sensitive to changes in length of sandlance >1 yr of age, with higher success when fish were larger. The mechanisms underlying these relationships are still unknown but it does appear likely that changing conditions as a result of climate change are important.
Effects of Invasive Species
Predatory mammals, such as foxes, upon access to breeding sites, cause major reductions in murre populations or delays in breeding which later adversely affect breeding success (346, 347, 192, 339). Presence of 2 red fox on Shaiak Island, Aleutian Islands, Alaska, caused loss of practically all eggs of 25,000 pairs during 1976; besides eggs taken by foxes, gulls also took them when pairs departed (551). Foxes introduced historically (for fur farming) to 455 Alaskan islands still remained on 46 islands by 1990 (552); on basis of surveys on 22 Aleutian islands, Murie (335) examined 2,501 arctic fox scats and found 58% bird remains, 1% of which were murres; actual percentage of consumed birds likely higher owing to differential rates of digestion between birds and other food groups.
Hunting and Trapping
Currently hunted in Newfoundland and Labrador from 1 September to 10 March, with 250,000–300,000 shot/yr from small boats (1997–1998: 5% Common Murres, 95% Thick-billed Murres [Uria lomvia], ca. 50% first-year birds; 553, 554). During 1970s–1980s, 600,000–900,000 taken/yr (553); meat eaten fresh or frozen; canned "turr" supported minor industry in 1940s–1950s (38), subsequently replaced in late 1960s–1970s by large, illegal sales (519, 547, 553). Beginning in 1993, harvest and illegal sale reduced by regulations (20 birds/hunter/d, over a maximum of 3.5 mo). Effect on populations not directly known, but current harvest unlikely to cause severe declines (47, 553, 48, 507; see Demography and Populations: Population Regulation). Although the number of hunted birds has decreased, the proportion of Common Murre in the hunt has increased in recent years (G. Robertson, ECCC-CWS). The winter hunt may also damage non-captured murres by increasing their energy output to evade hunters (555) since wintering birds are operating at a barely sustainable level of energy use (168).
Marked declines at 18 breeding sites in the Faeroe Islands, from 390,000 pairs in 1972 (556) to 300,000 by 1984 and further decreases to 100,000 pairs by 1997–1999 (557). Causes of declines multi-factoral, from intense egging and hunting through to drowning in fish-nets and changes in availability of principal fish prey from over-fishing and climate change (see 47; for magnitude of conservation problem, see 558). Conservation efforts presently underway: restrictions on hunting, egging, and disturbance at colonies during breeding season (e.g. Lyngs and Kampp 1996, for Danish waters). Also now a member of the Nordic Seabird Colony Database to enhance monitoring of murres and other seabird species in the Faeroes (559).
Commercial egging common in past, not much at present. An estimated 10 million eggs taken from Farallon Islands, California, during the period 1850–1900, with comparable numbers worldwide (560, 561, 562, 101). Commercial egging, along with disturbance, at Farallon Islands caused population to decrease from 200,000–500,000 pairs in mid-1800s to 45,000–90,000 pairs by 1896, when large-scale egging stopped; likely largely responsible for continued decline to <17,000 pair by 1911 (562, 99, 101). Egging also blamed for dramatic decline in Funk Island, Newfoundland population during 1874 to 1887; population rebounded when egging ceased (518). Egging and hunting all but exterminated colonies along North Shore of Gulf of St. Lawrence and southern Labrador during the late 1800s and early 1900s; despite conservation efforts, illegal egging and shooting remains significant, though declining, along lower North Shore (563, 535, K. A. Blanchard, personal communication) and southern Labrador (48). Eggs still taken sparingly in Alaska; e.g., 5–10 dozen/household/yr taken by community at Cape Thompson (564, 5). Commercial egging (~50,000 /yr) at Bempton Cliffs, northern England 1800–1954 resulted in population decline (565).
Direct Effects of Commercial Fisheries
Besides oil pollution, gill nets are the scourge of both murre species. Other than tallies of mortality (below), impact to populations difficult to perceive for same reasons listed below for oil-spill assessment.
U. a. inornata: Killed/year, northern Gulf of Alaska and Bering Sea: 1952–1978 (fishery phased out thereafter), surface salmon nets, 588–1,020 (566, 567), or as high as 1,850 (568); Prince William Sound, 332 (only 1990–1991 data available); Unimak Pass, 212 (both species, only 1990 data available; 569). Current total for Alaska may be higher, as few of the widespread coastal Alaskan gill-net fisheries monitored (569). Gill-net fisheries are likely in part responsible for the large decrease in murres in northern Japan waters (110).
U. a. californica: British Columbia: mortality likely widespread (e.g., Barkley Sound and Strait of Juan de Fuca in 1979-1981), but data incomplete (570, H. R. Carter, personal communication). Washington: murres make up 39–95% of all seabirds entangled; in 1994 alone, 2,713 killed in salmon fishery (surface nets) in the vicinity of the San Juan Islands (571; see also 572). California: central coast in 1979–1987, bottom nets deployed in shallow, inshore waters caught thousands/yr, with a peak of 25,000+ killed in 1983 (>75,000 murres total; 567, 573, 495, 574). Small fishery restrictions in 1982–1987 and major ones in 1988–1995 (due to concern about impacts on seabirds, especially murres, and marine mammals) closed fishing in various areas. Mortality substantially reduced (i.e., from 5,000 murres in 1986, to 2,600 in 1990, to 200 in 1994). Fishing effort in Monterey Bay increased thereafter, resulting in kills of 1,400–3,100 murres/yr in 1996–2000 (575, 576, 577, 578). Direct bycatch is 90% males, but orphaned chicks would die as well (Moss Landing Marine Laboratory July–August 1999, unpublished data data courtesy of H. Nevins). In September 2000, fishery restricted to >120 m, effectively closing it.
Unknown numbers of murres also taken in surface nets deployed off California (sharks; 568).
U. a. aalge: Mortality in Witless Bay and adjacent regions, Newfoundland, from surface salmon and bottom cod nets increased from low level in 1950s–1960s to 20,000–30,000 in 1971; with decrease in capelin stocks and demise of cod stocks (commercial fishing reduced), murre mortality decreased to ~8,000 by 1981 (579). Along the coast from Funk Island to Cape St. Mary's, 1981–1984, mortality of 22,070 estimated (580). Little monitoring elsewhere of extensive fisheries (e.g., Grand Banks), but evidence indicates high mortality (579, 580). The fishing industry is currently depressed due to collapse of cod and capelin fisheries (581) and the decrease in gill-nets have likely been the cause of recent increase in murre numbers (582). Similar development has been observed in northern Norway (107). Pre-1985, drowning in salmon drift nets and cod nets was a major source of mortality and population decline (583). Salmon drift nets were banned in 1989. Following an intense fishery from 1970–1985, the capelin stock in the Barents Sea collapsed in 1986, and as a result, the Common Murre population in the Barents Sea declined by 70–90% due to starvation during the winter 1986–1987 (107). Recently, the mortality in fishing gear has been relatively low (584).
Lost, abandoned, and discarded nets also a problem: e.g., one abandoned salmon net found near Agattu Island, Alaska, in 1979, had >400 drowned seabirds, including murres, entangled within it (568, 585, 586).
Pesticides and Other Contaminants/Toxics
In eggs from Farallon Islands, California, collected in 1968–1970, average concentrations of DDE (297 ppm), PCB (168 ppm), and dieldrin (0.021 ppm) were higher than in eggs collected in 1913 (401). Although shells were 13% thinner than normal (see Breeding: Eggs), no crushing or elevated prebreakage noted (DGA). In central Oregon, higher concentrations of chlorinated hydrocarbons (DDE; 8.7 ppm wet mass) in brain tissues of murres found dead on beach (during 1969 "die-off") compared to birds shot at sea (when no "die-off" in 1970; 1.1 ppm); PCB levels (4.0 ppm) also higher than in live birds (1.1 ppm). Above-normal levels of DDE found in brain tissue of dead murres also during a "die-off" in central California (478); sublethal levels during food stress, as in 1969, may contribute to mortality (488). In egg albumen from Farallon Islands, collected in 1993 (n = 15), levels of DDT (and derivatives; 8,200 µg/kg dry mass), PCB (and related compounds; 5,900 µg/kg), and mercury (550 µg/kg) elevated in accord with higher trophic level compared to various prey; lead and selenium present at low levels not in accord with trophic level (587); dioxins and dibenzofuran also noted, but not at toxicologically significant levels and not in accord with trophic level (587; see also 402). Recent measurements suggest that Common Murre and other seabirds have high mercury levels in eastern Canada (588).
Two main sources of oiling are the offshore petrochemical industry and oil from vessel bilge discharge (e.g., 489, 487). Significant mortality from oil pollution (petroleum) suffered during past 100 yr, for instance during World War II (105), and may well continue in many Atlantic and Pacific regions in accord with continental shelf drilling for oil (522, 322: Fig. 5.1, 101). The southern end of murres’ eastern North Pacific range coincides with many natural oil seeps (Santa Barbara Channel).
Mortality mainly due to hypothermia and malnutrition after oiled feathers lose insulating properties; upon ingestion during preening, toxic properties of oil exert longer-lasting effects (589, 590, 470, 591). Shock and stress lead to acute, deep anemia, which affects foraging abilities. Reproductive capacity reduced (reviewed in 470) and virus infection elevated (468).
In part, susceptibility to oiling drives much of the research on this species' natural history (e.g., 592, 593, 494). Among the most affected by oil pollution of all marine birds, because of (1) low reproductive rate, (2) large populations, (3) dense concentrations in coastal habitats (coincident with major shipping channels), and (4) persistent presence on the water (594, 273, 595, 596, 91; see Habitat; also Demography and Populations). Since mid-1980s in eastern North Pacific, a specialized group of agency and private personnel have assessed impacts of spills to seabirds (e.g., 528, 597, 598, 273); agencies then attempt to recover financial compensation for injury to natural resources along with fines and other forms of financial mitigation.
No portion of northern North American coast where murres occur has been exempt from major kills due to oil spills during past 50 yr (522, 217). Mortality estimates before 1980 mostly rough body counts; later ones based on sophisticated models considering oil trajectories, densities at sea, body counts, and estimated proportions reaching shore and being recovered (597, 599, 600). Known major kills (>2,000 murres) occurred in eastern Canada: 1951, 1970, and 1979 (601); Alaska: 1970 and 1989 (590, 600); southwestern Canada and northwestern United States: 1956, 1988, and 1991 (602, 603, 604); California: 1937, 1971, 1984, and 1986 (597, 599). Other notable murre kills from oil spills in California waters occurred after 1996 (H. R. Carter, unpublished data).
Long-term beached-bird surveys indicate chronic oiling, often without known point source of oil (cf. 322: 28–29). Proportion of murres found oiled: 3–78% of beached birds (e.g., see 601, 480, 602). Off Newfoundland, oiling rate of murres (Thick-billed and Common) found dead was likely highest in the world at large regional scale (605); the estimated annual mortality of murres (Thick-billed and Common) and Dovekie (Alle alle) due to chronic oil pollution in Newfoundland was on average 315,000 ± 65,000 from 1998–2000 (606; 0.77 birds/km, 607). Oiling, measured as total number of oiled birds per kilometer of shoreline, showed a decrease from 1984 to 2006 in Newfoundland, possibly due to better laws and enforcement related to emissions from ships. Oiling rates (number of oiled birds/total number of dead beached birds), however, appears to have increased in summer counts since 1984, but this apparent increase is due to a lower number of unoiled dead birds in the samples. The lower number of unoiled dead birds likely reflects a reduced legal murre hunt and fewer birds drowning in gill-nets. Despite this decrease, the waters around Newfoundland still have a higher number of oiled birds than elsewhere in Atlantic Canada (607).
To monitor the adverse effects of chronic oil pollution on seabirds, beached bird surveys have been conducted in the North Sea since the 1960s (608). In the 1960s, 99% of the beached murres in the North Sea were oiled. The percentage of oiled murres has declined gradually, and was around 19% in the 2010s (609, 608). The decline suggests a consistent decline in chronic oil pollution and consequently reduced impacts on seabirds in the North Sea. In addition to chronic oil pollution, a series of oil spill incidents from wrecked oil tankers have killed a large number of Common Murre in Europe. The Erika accident, December 1999, Bay of Biscay, France, killed 60,000–120,000 Common Murre (610). The Prestige accident, November 2002, Galicia, Spain, killed 26,000–80,000 Common Murre (611). Four oil spill incidents occurring from Galicia to Wales in the period 1992–2002, were associated with a doubling of the mortality of adult Common Murre breeding on Skomer, Wales (596). Non-breeder survival was less affected, and increased immature recruitment compensated for the losses of adult breeding birds (91).
The Exxon Valdez oil spill, March 1989, Prince William Sound, Alaska, for such a relatively small spatial scale resulted in the largest murre kill yet recorded (185,000 birds; 600). Many biologists assessed impacts, including detailed follow-up studies and monitoring (612, 613, 614, 615). Breeding populations and success was depressed (e.g., Barren Island), and timing of egg-laying delayed annually until 1993 (616). Estimates of pre-spill populations imprecise, thus no good measures of population change; many murres wintering from northern Alaska and nonbreeders in spill area at the time (617, 618). Densities at sea in oiled areas depressed slightly and only within 1 year of the spill (613).
In general, effects of spills or chronic pollution on populations difficult to discern owing to sparse data on total mortality, pre- or post-spill colony size, other contributing factors (e.g., gill nets or climate change) and, as most oil-related kills occur during winter, links between wintering and breeding populations; best examples of effects at central California colonies (Farallon Islands) and Cape St. Mary's, Newfoundland (522, 101). Long-term monitoring and studies needed to better demonstrate impact of oil pollution on murre populations.
Ingestion of Plastics, Lead, Etc.
Rarely may swallow small pieces of plastic floating on sea surface; not a problem for this species, which does not normally scavenge dead prey (586). In North Pacific, prevalence of plastic in gizzards increased from 0% in 1969–1977 (n = 191; 619) to 0.8% in 1988–1990 (n = 134; 620).
Because this species breeds in the open at high density and with no nest, human intrusion into or near breeding subcolonies, if not done cautiously, reduces breeding success due to temporary desertion and loss of eggs and chicks to predators, as experienced during commercial egging operations (561, 621, 38, 99, 47, 622). Disturbance from research activity can be high, but level of impact can be maintained at a minimum through careful selection of timing and manner of movement/activity: e.g., numerous breeding and banding studies performed in eastern Canada and Scotland with minimal disturbance (cited throughout present report). Overall, investigators must adhere to rigorous rules, written and unwritten, to ensure future welfare of study subjects.
In the case of radio telemetry and satellite telemetry, external antennae significantly alter breeding behavior (e.g., frequency and length of absence from breeding site) and affect breeding success beyond capability of mates of instrumented birds to compensate (623, 149). Data derived from early telemetry studies, especially on breeding birds, must therefore be interpreted and used with caution. Logger devices are now much smaller than they were 20 years ago (2000 and earlier) and are now attached to leg bands instead being glued to the bird’s back, where likely they interfere with hydrodynamics (624). The decrease in device size and weight reduces the behavioral effects of loggers, allowing us to focus on the new information they provide (e.g., 90, 92).
Protected under Migratory Birds Convention Act of 1916 between Canada, Mexico, and United States, the Wildlife Act (in Canada), and many other U.S. federal and state statutes. The European Union under the Birds Directive has protected murres and other seabirds since 1979, and their habitats under the Habitats Directive since 1992.
Measures Proposed and Taken
Oil-Fouling. Increased control of oil industry due to public pressure (often result of TV images of oiled birds) for increased government regulation resulted in: non-approval and curtailment of continental shelf oil-drilling leases in highly productive biological areas (e.g., Lancaster Sound, eastern Canadian Arctic), initiation of ship traffic control in high-traffic areas, double hulls for tankers, prohibition of releasing ship ballast (oily water) in coastal areas, and installation of oil-slick curtailment measures in all major harbors (322). After every spill, since late 1960s, oiled birds still alive have been cleaned and released within a few days, but survival rate is low (e.g., 625; see below). Off eastern Canada, oil-drilling on continental shelf continues to expand, as does chronic oil pollution (494, 48, 605); far more stringent regulations required on petroleum activity and transport (605). An Amendment to the Canadian Migratory Birds Convention Act increased surveillance, enforcement, and penalties for vessels discharging oily bilge water within the 200-mile limit (607), but it remains very difficult to totally prevent discharges. Burke et al. (626) recommended having industry-independent observers, rather than industry workers, on oil rig platforms to monitor effects on seabirds and other marine wildlife from spills, flares, and collisions.
Commercial Fisheries. Use of gill nets increasingly curtailed in coastal areas of California to reduce by-catch of birds, mammals, and non-target fish (e.g., 574, 578). Experiments in Puget Sound, Washington, with salmon gill-net fishery indicate that murre by-catch could be reduced 40–45% if visual panels and/or acoustic pingers incorporated into all nets (198). A fishery-management plan written for shortbelly rockfish (Sebastes jordani) off California, with ecosystem considerations in mind, restricted fishing, as juvenile rockfish are important forage for salmon (Onchorhynchus spp.), seabirds including murres, and other predators (627, 628, 629). Although current gill-net use near Newfoundland is low following collapse of stocks of the major commercial fish species (Atlantic salmon and northern cod), it remains important to prohibit any future gill-net deployment near capelin ‘hotspots’ (630) and, if they are used, to have gill-net-free buffer zones around murre colonies or have nets only deployed after chicks leave the area (630, S. Wilhelm and G. Robertson, ECCC-CWS). Murre populations in the northwest Atlantic have generally increased since the cod moratorium in 1992 (fewer nets), while the population sizes of surface feeders (less available fish offal) have declined (582). That trend is likely reversing by 2020 with the increase in predation and the decrease in reliable capelin spawning leading to decreased breeding success (see also 109).
Colony Restoration. Direct colony restoration possible through reduction of moderate to high levels of mortality and human disturbance; indirect restoration possible through research, general management (e.g., habitat protection and enforcement), and education. Good examples are programs along North Shore of the Gulf of St. Lawrence (563, 535) and in National Wildlife Refuges on U.S. West Coast. Active colony restoration possible (see below).
Effectiveness of Measures
Noted above (Population Status), although increases and decreases have been noted at regional scales, the global murre population appears to have changed little. In part this is through control of oil pollution, eradication of introduced mammals from islands, and alteration of fishery practices. Recent changes in food webs owing to climate may be having an initial negative effect.
Oil Fouling. Off eastern Canada, percent of oiled alcids increased by 2.6%/yr during 1980s and 1990s (605). Post-released birds significantly lighter than non-oiled individuals, indicating compromised survival (31). Post-spill cleaning of oiled murres continues, but not effective over long term judging from high mortality of rehabilitated birds (as per band recoveries); post release life expectancy 9.6 d, survival 10–20% of released non-oiled murres up to late 1980s (631). Recent efforts to improve oiled wildlife rehabilitation extensive with some positive results (e.g., 22% survival; 632). Changes in Canadian laws and enforcement are thought to be related to the decreased number of beached oiled birds (607, 633), but the incidence of beached oiled birds around Newfoundland is still higher than in other areas in eastern Canada.
Colony Restoration. Effectiveness of passive or active restoration (or even natural recovery) of colonies dependent on health of regional population (161). "Passive" efforts successful as long as all elements of management plan followed: management of colonies on North Shore of the Gulf of St. Lawrence resulted in growth from few birds in 1920s to 5,000 pairs by 1977 and 13,000 by 1988; as soon as efforts relaxed, colonies declined (563, 535), but overall, numbers rebounded since 1984 to reach highest level (20,000 pairs) since 1800s (514, 515, 505; see Appendix 5). Reduction of mortalities by fishery closures and reduced oil pollution led to partial population recovery in central California in 1990s, especially at large colonies (Farallon Islands, California; 249).
Social-attraction techniques (i.e., decoys, mirrors, and call playback) successful at small colonies. Devil's Slide Rock, California, a small nearly extirpated colony (about 1,500 pairs in 1980), reinitiated in 1996 (with social-attraction techniques); grew to 100 pairs by 2001; colony did not appear to be re-establishing itself naturally after extirpation (101, 383).
Fishery Effects. Restoration of key forage species by altered fishery management has provided more resiliency in murre populations to cope with various other impacts, and has led to population recovery in certain regions, such as in the California Current (102, 82, 83, 249) and in the North Atlantic (104, 109).