Black-footed albatross (Phoebastria nigripes) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

Like most pelagic seabirds, Black-footed Albatross are a long-lived, K-selected species with small clutch size and low fecundity (typically < 0.5 chicks reared per breeding pair per year; Whittow 1993; Furness 2003), slow chick growth and lengthy parental care period, delayed age of first breeding, and high adult survival rates (often > 90% per annum for most species) and are thus highly vulnerable to adult mortality. In contrast, a change in reproductive output will likely have a much smaller impact on population dynamics and will require a considerable time lag to become apparent (Tasker et al. 2000; Furness 2003).

Historically, the greatest threats to Black-footed Albatross consisted of poaching by feather and egg hunters, with the loss of as many as 300,000 birds per year between the late 1800s and early 1900s (reported in Lewison and Crowder (2003) based on Rice and Kenyon (1962b), Spennemann (1998), and Cousins and Cooper (2000)). Other important historical threats included alteration of habitat through military occupation and the introduction of domestic rabbits and non-native vegetation, and population control of nesting birds during wartime preparations and subsequent military operations (McDermond and Morgan 1993; Cousins and Cooper 2000). In the 1950s and 1960s control programs to protect aircraft at Midway, as well as collisions with buildings, antennae and other infrastructure, resulted in the death of tens of thousands of Black-footed and Laysan albatrosses (USFWS 2005a).

Approximately 90% of the world’s Black-footed Albatross population breeds at only four sites (Laysan Island, Midway Atoll, Pearl and Hermes Reef and French Frigate Shoals; USFWS 2005a), so the species is particularly vulnerable to localized threats during the breeding season (e.g., oil leaking from vessels sunk in WW II; USFWS 2005a). However, non-breeding adults and immature birds remaining at sea year-round serve as a potential “extirpation buffer” to local stochastic events.

Bycatch in longline and driftnet fisheries

Fisheries bycatch is a global concern for many species of wildlife and fish because of the incidental take of non-commercial species while fishing for commercially valuable species (Hall et al. 2000; Tasker et al. 2000; Furness 2003; Gilman and Freifeld 2003; Lewison et al. 2004). Incidental catch in longline fisheries has been an international conservation concern for seabirds for over two decades, especially in the Southern Ocean where 17 albatross taxa have been affected (e.g., Weimerskirch and Jouventin 1987; Brothers et al. 1999; Gilman et al. 2005). Today, longlining is one of the most common fishing methods used worldwide, and comprises the greatest industrial fishing effort in the North Pacific (USFWS 2005a).

In the North Pacific, industrial longline fishing has increased steadily since World War II, and occurs in both national and international waters. On the west coast of the U.S. and Canada, six commercial longline fisheries overlap with Black-footed Albatross populations during and after the breeding season: the pelagic tuna (Thunnus spp.) and swordfish (Xiphias gladius) fisheries near their colonies in Hawaii; the demersal groundfish fishery in the Bering Sea/Gulf of Alaska; the demersal Pacific halibut (Hippoglossus stenolepis) fishery in Alaska; and the demersal rockfish (Sebastes spp.) and halibut fisheries in British Columbia (Melvin et al. 2001; Smith and Morgan 2005). At least six seabird species have been reported caught in these fisheries, including all three North Pacific Albatross species, with Northern Fulmars (Fulmarus glacialis) and Laysan Albatross the most common in Alaska, and the Black-footed Albatross the most common in British Columbia (Melvin et al 2001; Smith and Morgan 2005). Observer coverage in these fisheries ranges from 0% of hooks hauled (US halibut) to 19% (Canadian halibut; Smith and Morgan 2005).

In the Hawaiian-based fishery, at least 23,000 Black-footed Albatrosses were killed from 1990–1994 (USFWS 2005a). In the five years following, 1994–1998, a further 6,827–11,622 birds were caught (Cousins and Cooper 2000).  In the Bering Sea/Gulf of Alaska, the groundfish fishery caught an estimated 310–600 Black-footed Albatross annually during 1993–1997 (Stehn et al. 2001; Melvin et al. 2001).  These data suggest that 1% of the global Black-footed Albatross population was taken annually in the 1990s (Cousins and Cooper 2000). Lewison and Crowder (2003) calculated that between 5,200 and 13,800 Black-footed Albatross per annum were caught in the 1990s over the entire North Pacific Ocean based on fisheries observer data for the US pelagic longline fleet and estimates of Japanese, Taiwanese and Korean fishing effort. This estimate is controversial because there are no observers on US halibut or international vessels, and < 5% observer coverage in the US groundfish fishery. Satellite tracking of four Black-footed Albatrosses captured off California found a high degree of spatial overlap between albatross distributions and reported fishing effort in the 1980s but no co-occurrence with effort in the 1990s (Hyrenbach and Dotson 2003). These results might suggest that Black-footed Albatross mortality was higher in the 1980s than the 1990s.

In Canada, the Black-footed Albatross is the seabird species most at risk of bycatch due to a high degree of spatial and temporal overlap with longline fishing effort (Wiese and Smith 2003; Smith and Morgan 2005). A spatially and temporally explicit analysis of the halibut and rockfish fishery from 2000–2002 estimated an annual mortality of 55–253 Black-footed Albatross, accounting for uneven observer effort and coverage (Wiese and Smith 2003). This estimate represents 2–4% of the Canadian maximum annual summer population of 2,500–4,000 individuals, as identified by Morgan et al. (2000).  Bycatch rates for the Black-footed Albatross in B.C. (2000–2002), ranged from 0.0007–0.0054 (halibut) to 0–0.316 (rockfish) birds killed per thousand hooks (Wiese and Smith 2003). The estimated bycatch rates in Canada are lower than the US swordfish fishery (0.16–0.59), comparable to the US tuna fishery (0.005–0.024) but twice as high as the Alaskan groundfish fishery (0.0002–0.015; Melvin et al. 2001; Lewison and Crowder 2003). The difference in total annual mortality of the Black-footed Albatross between the US and Canada is due to a smaller fishing area and fewer licensed vessels.

Longline fishery effort, target areas, and regulations related to bycatch are often in flux, at least in terms of Canadian- and US-based fisheries. For example, in response to seabird bycatch, British Columbia, Alaska and Hawaii have all implemented mandatory mitigation measures since the late 1990s.  In 2001, primarily due to the mortality of marine turtles, the Hawaiian-based longline fishery for swordfish was closed and subsequent estimates of Black-footed Albatross bycatch dropped to under 100 birds per year.  However, much of the Hawaiian swordfish fleet then moved to California, since mitigation measures were not yet required for California-based vessels despite considerable overlap in fishing areas, and Black-footed Albatrosses were caught in that fishery (72 birds caught during 469 net sets; US National Marine Fisheries Service 2004). Californian boats were regulated in 2004 and effort shifted back to Hawaii when the swordfish fishery was re-opened (USFWS 2005a). In Alaska, regulations adopted to prevent the accidental take of Short-tailed Albatross have reduced total bycatch significantly (Melvin pers. comm. 2006). In Canada, regulations for the mandatory use of seabird avoidance measures in longline fisheries were adopted in 2002; however, there have been no studies to assess the effectiveness of the regulation.

Until a moratorium in 1992, the high seas squid driftnet fishery in the North Pacific caught an estimated 3,500–4,500 Black-footed Albatrosses per year (Johnson et al. 1993). Legal North Pacific drift gill net fisheries still occur for salmon, and illegal driftnet fisheries target squid. The incidental take of shearwaters and alcids has been documented in the legal fisheries in the literature (e.g., Uhlmann et al. 2005). The legal fisheries occur west of 180° and may affect post-breeding Black-footed Albatross during dispersal from Hawaii and breeding birds foraging from colonies in Japan. There are no data for the illegal fisheries except reports from US Coast Guard personnel monitoring the area with aircraft surveillance: Laysan Albatross have been reported as bycatch (D. Hyrenbach pers. comm. 2006).

Competition with commercial fleets is another possible fisheries interaction for Black-footed Albatross. As squid forms up to 30% of their diet, Black-footed Albatross compete for food with pelagic squid fisheries.  As is likely the case with Short-tailed Albatross (USFWS 2005c), the effect of commercial fisheries on the Black-footed Albatross food base is probably discountable. Scavenging is an important foraging strategy for Black-footed Albatross and any competition is likely offset by access to fisheries discards (cf. Tasker et al. 2000; Furness 2003).

Entanglement in “ghost” (lost or discarded) fishing gear such as monofilament nets has been documented for other marine birds (Tasker et al. 2000) and is a possible cause of mortality for Black-footed Albatross, although there are no data on this risk factor for the species.

There are few demographic data from dead Black-footed Albatrosses with which to estimate the population level effects of fisheries bycatch. However, a salvage bird program in British Columbia that retained thirteen Black-footed Albatrosses from 2002-2003 found that of 13 birds (7 males, 6 females), 12 were juveniles or immatures based on bursa and plumage (Environment Canada unpubl. data). Fisheries mortality can compound other demographic effects including mate loss. In the Black-footed Albatross, mate loss can cause adults to miss up to five breeding seasons prior to forming a new pair, decreasing lifetime reproductive success (Lewison and Crowder 2003; Mills and Ryan 2005).

Oil spills

Seabirds in British Columbia waters are vulnerable to both smaller chronic and larger catastrophic oil spills (Burger et al 1997). In general, seabirds are more at risk from smaller chronic spills (including deliberate discharge of oily waste) than from large, catastrophic ones as timing, frequency and location of spills are better predictors of impact than is spill size alone (Burger 1993; Wiese and Robertson 2004). Black-footed Albatrosses are susceptible to oiling as they often congregate on the water when foraging, especially around fishing vessels (see Behaviour section). Oiling of Black-footed Albatrosses does occur, even with this highly pelagic species – for example, oiled adult birds have been observed at the Tern Island colony (Chisholm pers. comm. 2006). Oil spills or discharges in or near key foraging areas (e.g., upwelling in the vicinity of shelf breaks) could pose a particularly high risk to Black-footed Albatrosses and other offshore seabirds.

Areas potentially involved in any future offshore oil and gas exploration in Canada’s Pacific coastal waters include Queen Charlotte Sound and areas within Hecate Strait and off the north coast of Vancouver Island (COSEWIC 2004; Reid pers. comm. 2006). These areas overlap with marine habitat use of Black-footed Albatross in Canada (Figures 4 – 9); if offshore exploration for oil and gas leads to any petroleum spills or discharges, the potential for these affecting seabirds such as the Black-footed Albatross is substantial (COSEWIC 2004). Certain levels of hydrocarbon discharges are permissible during offshore oil and gas production and these can often lead to light sheens around offshore rigs. Black-footed Albatrosses innately investigate everything on the ocean from flotsam to ships, so will certainly be attracted to oil derricks as other seabirds are known to be (O’Hara pers. comm. 2006).

Existing commercial vessel traffic (tanker, cargo/passenger, fishing vessels) poses an ongoing oil spill risk for coastal BC waters through collision, grounding, or illegal disposal of oily bilge waste. A study by the Pacific States/British Columbia Oil Spill Task Force (2002) found areas of higher grounding or collision risk 25 nautical miles from land along the entire West Coast, except (for Canadian waters) off northwestern BC, where the high risk area extended to 100 NM offshore. Most west coast tanker traffic remains well offshore as a result of a voluntary tanker exclusion zone; however, non-tanker traffic uses shipping lanes that parallel the shelfbreak off the west coast of Vancouver Island and the Queen Charlottes (O’Hara pers. comm. 2006).

Coastal shipping in British Columbia waters – including vessels transporting oil and condensate – is projected to increase dramatically within the next decade. For example, the proposed Kitimat pipeline (projected completion date 2010) would transport heavy oil across BC from Alberta’s oil sands to the West Coast for export by oil tankers to Asian (China) and US southern markets (California). Projected volume would require a 125,000 DWT oil tanker every second day. The pipeline proposal also includes the importation (from offshore sources to Kitimat) of up to 25,000 barrels of condensate per day, and transport by existing CN railway to Alberta. The proponent expects to start importing by 2006. Similar proposals for new or expanded port facilities exist for coastal communities such as Prince Rupert and Stewart (Reid pers. comm. 2006).

Climate change and natural climate cycles

Climate change is primarily likely to affect albatrosses and other marine birds through intensification of El Niño Southern Oscillation (ENSO) events, leading to less productive marine foraging habitat (Robinson et al. 2005; see also Habitat trends, above). Mass adult mortality due to climate-induced food shortages has been documented in pelagic waters for Short-tailed Shearwater (Puffinus tenuirostris; Baduini et al. 2001), but decreased food availability and/or quality can also decrease reproductive success of breeding seabird adults or survivorship of fledged offspring (Crick 2004; Kitaysky et al. 2006). Black-footed Albatrosses may conceivably choose to increase intervals between breeding years due to depleted food resources (Gilman and Freifeld 2003). Climate change effects have not yet been documented for breeding Black-footed Albatrosses, although there has been a decrease in the number of this species recorded in the California Current system, concurrent with an apparently minor PDO-linked increase (0.7 ºC) in average sea surface temperature (Ainley and Divoky 2001; Crick 2004; see Habitat trends section).

Sea level rises associated with climate change may ultimately decrease the availability of nesting habitat at the low-lying atolls where a high proportion of the global population of Black-footed Albatrosses breed. The low elevation islands of the tropical Pacific are among the world’s most vulnerable sites to climate-induced inundation (USFWS 2005a; Baker et al. 2006).

Contaminants

As a long-lived top predator, Black-footed Albatrosses are susceptible to the bioaccumulation of environmental pollutants that are ingested via prey items. Black-footed Albatross appear to feed at a higher trophic level than Laysan Albatross (Gould et al. 1997, 1998; though see Finkelstein et al. 2006), and contain correspondingly higher concentrations of organochlorines and heavy metals (e.g., PCBs, DDE, mercury; Auman et al. 1997; Guruge et al. 2001; Shinsuke et al. 2003; Finkelstein et al. 2006). Black-footed Albatrosses are also likely to accumulate organochlorines such as PCBs via consumption of floating plastic items, which they ingest frequently (see Plastic ingestion section, below). Using samples collected in 1992–1993, Auman et al. (1997) found that concentrations of DDE in the eggs of Black-footed Albatross from Midway were at about half of the threshold required for eggshell thinning, although population-level thinning effects had not been observed. Concentrations of PCBs, DDE and dioxins in Black-footed Albatrosses were similar to those for certain terrestrial and coastal bird species at contaminated sites in industrial nations, e.g., the Great Lakes, with PCB concentrations being at the threshold of where subtle population-level effects on productivity could be expected to occur (Auman et al. 1997; Tanabe et al. 2004). However, samples collected at Midway in 2000 showed a marked increase in blood plasma concentrations of contaminants over those reported by Auman et al. (1997), with DDE concentrations 360% higher than in 1992–1993 samples (Finkelstein et al. 2006). The US Fish and Wildlife Service (2005a) presently reports a “small but measurable reduction in productivity” at Midway Atoll as a result of organochlorine contamination in combination with fisheries bycatch.

Birds at Midway Atoll are also locally exposed to lead in paint chips around old buildings. Chicks ingest contaminated soil and the resulting lead poisoning results in poor fledging success since poisoned birds are unable to fly, although to date this has only been documented in Laysan Albatross (Finkelstein et al. 2003; USFWS 2005a).

Plastic ingestion

Far-ranging surface feeding seabirds such as Black-footed Albatrosses are known to consume substantial amounts of floating plastic waste, to the extent that pelagic tubenoses such as albatrosses and Northern Fulmars have been suggested as biological indicators of marine plastic pollution in the world’s oceans (Nevins et al. 2005; van Franeker and Meijboom 2002). Susceptibility to plastic consumption has been ranked “high” for Black-footed Albatross (Nevins et al. 2005), with 100% of birds examined in two studies containing plastic in the gizzard and/or proventriculus (Blight and Burger 1997; Kinan and Cousins 2000). Of 13 Black-footed Albatross sampled off the British Columbia coast, 8 had plastic in their stomach (Environment Canada, unpublished data). Adult birds can regurgitate plastic items and thus offload them while provisioning offspring, but young chicks do not possess the musculature to do so and therefore retain plastic loads until near to fledging. Items ingested by albatrosses include cigarette lighters, bottle tops, rubber gloves, plastic toys, broken plastic fragments, industrial plastic pellets and chemical light sticks (Blight and Burger 1997; Auman et al. 1998; Nevins et al. 2005). Although it has proven difficult to determine whether there are population-level impacts of plastic ingestion by seabirds, individual effects documented for North Pacific albatross species include lower fledging masses, reduced fat indices, satiation and subsequent starvation or dehydration, and mechanical blockage of the gut (Sievert and Sileo 1993; Auman et al. 1998; Nevins et al. 2005). Plastic in the ocean adsorbs organochlorines such as PCBs, and dietary plastic likely increases albatross exposure to these and other toxic compounds (Auman et al. 1998; Tanabe et al. 2004). Available research shows an increasing trend in plastic ingestion by seabirds worldwide (Nevins et al. 2005).

Invasive species

Introduced vertebrate predators pose a globally serious conservation threat to island-nesting birds. Rats are known to depredate Black-footed Albatross nestlings (see Predation section), but have been eradicated from most islands where the species is nesting. Feral cats (Felis catus) and rats are still present at islands that were historically occupied by Black-footed Albatross (e.g., Wake and Johnston Atolls and the Mariana Islands), and may prevent or limit re-colonization of these sites. Cat eradication is underway for Wake Island (USFWS 2005a). Mosquitoes (Culex quinquifasciatus) were introduced at Midway Atoll during WW II. These insects are a vector for avian pox and Midway is the only albatross colony where outbreaks of this disease occur (Tickell 2000; USFWS 2005a; see Diseases and parasites). As albatrosses have had little exposure to mosquito-borne viruses they may be particularly vulnerable to the emerging threat of West Nile virus (USFWS 2005a), although there are no data to support this supposition.

Invasive alien plants can eliminate or degrade habitat for ground-nesting seabirds. Ironwood and golden crown-beard form dense forests or stands at Midway, limiting the open sandy areas favoured by Black-footed Albatrosses (see Habitat trends, above). Golden crown-beard also has displaced large areas of native vegetation at Kure Atoll and Pearl and Hermes Reef, and threatens to spread further in the Northwestern Hawaiian Islands. Management of these species by the USFWS is ongoing (USFWS 2005a).

Other threats

Other threats to the Black-footed Albatross are more localized in nature, e.g., birds nesting on volcanic Torishima and San Benedicto Islands are at risk from future volcanic eruptions (Whittow 1993; Pitman and Balance 2002). Air strikes continue to be a source of mortality for albatrosses at Midway Atoll, but strict mitigation measures are in place and birds are escorted or physically removed from the runway prior to aircraft landing or taking off; mortality numbers in the 10s of birds per year (numbers for Laysan and Black-footed Albatross combined; USFWS 2005c).

Offshore wind farms are being planned along the coast of British Columbia. One facility, the Nai Kun Wind Farm, is well into the planning phase and can provide a general perspective on the scope of similar projects. This wind farm will be built in Hecate Strait along the northeast coast of Graham Island. The Nai Kun Wind Farm is expected to contain 200 (and perhaps as many as 300-500) turbines and occupy many km² of marine habitat. Although technology continues to evolve rapidly, turbines will stand over 100 m tall with three blades and a rotor-swept diameter of up to 120 m. Turbine blades tend to not reach closer than 20 m above the ocean surface.

Two potential threats of wind farms to Black-footed Albatrosses are mortality from collisions or habitat displacement. Based on studies of other migrating waterbirds at wind farms in Denmark (e.g., loons, seaducks and geese), collision risk is believed to be very low for all birds. Birds detect turbines at distances greater than several hundred metres and either fly around or between the wind turbines (e.g., Christensen and Hounisen 2005; Desholm and Kahlert 2005). One risk assessment for procellariiform birds concluded that Northern Fulmars had the lowest risk of collision compared to all other marine bird species studied (Garthe and Hüppop 2004). Albatrosses and petrels tend to fly very close to the water’s surface (i.e., less than 30 m height of blade edge) and generally tend not to fly at night when visibility is reduced.

Habitat displacement could occur if albatrosses avoided marine habitats used by wind farms. However, marine wind farms are generally constructed in shallow waters and Black-footed Albatrosses normally frequent deep or shelf break waters (see Habitat); thus, relatively few albatross are expected to occur where wind farms are built.

Cumulative effects

The IUCN lists the Black-footed Albatross as Endangered because of a projected population decline of more than 60 percent over three generations (BirdLife International 2004a,b). While the validity of the worst-case scenario (i.e., the 60% decline in three generations, or a decline from 60,000 to 24,000 pairs) published by Lewison and Crowder (2003) is still unclear as new assessments (e.g., Arata et al. in review) were not available at the time of this draft, several facts make it clear that there is justifiable concern for this species: there is a high degree of interannual variability within the number of breeders returning to the colony each year even though long-term averages appear relatively stable; there are multiple documented threats that affect annual adult and chick survival; they are the third-most commonly reported seabird species caught as fisheries bycatch in the North Pacific (and the most commonly reported species caught in Canadian fisheries); and there is near-unanimous agreement among scientists in the US and Canada that there is a large amount of uncertainty surrounding estimates of mortality in foreign pelagic longline fisheries. We recommend a precautionary approach because of the multiple threats, the degree of uncertainty surrounding total mortality, and the high variability in the number of adults returning to breed each year. There is no doubt that sustained adult mortality from human activities can cause severe population declines in long-lived seabirds (Moloney et al. 1994; Weimerskirch et al. 1997; Tasker et al. 2000; Tuck et al. 2001; Ainley and Divoky 2001). As shown by examples in Hawaii (Cousins and Cooper 2000), and South America (Duffy 1983), the coincidence of unfavourable environmental conditions, and sustained, negative anthropogenic effects can cause population declines even when species are abundant. At the very least, decreased population growth (even when no declines are present) increases the vulnerability of these species and populations to changes in their environment and other pulse perturbations (Dunnet 1982; Takekawa et al. 1990; Wiese et al. 2004).

Page details

Date modified: