The black-footed albatross (Phoebastria nigripes) and the Laysan albatross (Phoebastria immutabilis) are two closely related seabird species that belong to the albatross family Diomedeidae. Both species are large, pelagic birds with long, narrow wings adapted for soaring over the open ocean. They are among the most widespread and abundant albatross species in the North Pacific Ocean. While the black-footed and Laysan albatrosses share many similarities and overlap substantially in their range, there are also several key differences between these two species when it comes to their appearance, breeding behaviors, habitat preferences, conservation status, and more.
Taxonomy and Physical Description
The black-footed albatross and Laysan albatross were previously considered to be subspecies (Phoebastria nigripes nigripes and Phoebastria immutabilis immutabilis). However, based on genetic evidence and behavioral differences, ornithologists now classify them as two distinct species within the same genus Phoebastria. Both species belong to the diverse Procellariiformes order which includes petrels, fulmars, shearwaters, and other tubenose seabirds.
In terms of physical appearance, black-footed albatrosses are named for their blackish colored feet. Adult birds have a dark grayish-brown back and upper wings, white undersides and head with a black smudge behind the eye, and a large pinkish bill with a dark tip. Their wingspan reaches up to 7 feet. Laysan albatrosses are slightly smaller with a wingspan around 6 feet. They have an all white head and underparts. The back and upper wings are blackish-brown. The bill is pink with a dark tip like the black-footed. Juveniles of both species have darker plumage overall with a black bill.
| Feature | Black-footed Albatross | Laysan Albatross |
|---|---|---|
| Scientific Name | Phoebastria nigripes | Phoebastria immutabilis |
| Wingspan | Up to 7 ft | Up to 6 ft |
| Weight | 5-8 lbs | 4-8 lbs |
| Plumage | Dark gray-brown back, white underside, black feet | Black-brown back, white head and underparts |
| Bill Color | Pink with black tip | Pink with black tip |
Range and Distribution
The ranges of the black-footed and Laysan albatrosses overlap substantially across the North Pacific, however there are some key differences.
Black-footed albatrosses nest on islands off the west coast of North America, including the Hawaiian Islands, and have a pelagic range across the northern North Pacific. They can be found from southern California to Alaska and across to Japan and eastern Russia.
Laysan albatrosses have a more concentrated distribution nesting on small islands in the Hawaiian archipelago and northwest Hawaiian Islands. They range widely across the central and northern North Pacific from Midway Island to the Bering Sea and Japan.
There is considerable overlap between the species around the Hawaiian Islands, Midway Atoll, and other central Pacific islands. However, black-footed albatrosses extend further north and south along the North American coast. Laysan albatrosses are more concentrated in the Central Pacific with higher densities overall around their core breeding islands.
Breeding and Nesting
The breeding ecology and nesting behaviors of these two albatross species also show some notable differences:
– Nesting islands: As mentioned above, black-footed albatrosses nest on islands off California, Oregon, Washington, and extensively through the Hawaiian archipelago. Laysan albatrosses nest exclusively in the Hawaiian Islands and northwest Hawaiian Islands like Midway, Laysan, and Kure Atoll.
– Mate choice: Black-footed albatrosses are known to pair for life with a single mate year after year. Laysan albatrosses may switch mates more frequently between breeding seasons.
– Nesting habitat: On islands where they co-occur, black-footed albatrosses tend to nest in more open, exposed habitats on slopes and ridges. Laysan albatrosses often nest in dense vegetation and shrubs.
– Breeding season: Laysan albatrosses begin breeding earlier, starting in October through June. Black-footed albatrosses breed from November through July.
– Nest construction: Laysan build more elaborate nests out of vegetation dominated by grasses and shrubs. Black-footed nests are simpler with less sturdy construction.
– Egg laying: Laysan albatrosses lay just a single egg per season. Black-footed often lay two eggs with about 4-5 days between them.
So in summary, Laysan albatrosses begin breeding sooner, build more sturdy nests, and lay just one egg in more vegetated habitats on their core islands. Black-footed have a longer breeding season, lay two eggs in simpler nest sites, and nest on a broader range of islands.
Foraging Ecology and Diet
The foraging ranges of both black-footed and Laysan albatrosses overlap substantially across the North Pacific. However, there are subtle differences in their diets and foraging strategies:
– Primary prey: Both species feed on squid, flying fish, crustaceans and other marine invertebrates. However, black-footed albatrosses rely more heavily on squid and have a greater proportion of squid in their diet compared to Laysan albatrosses.
– Foraging method: Black-footed albatrosses are more likely to actively pursue and dive for prey. Laysan albatrosses use a strategy called sit-and-wait foraging where they locate prey from the air and swoop down to the surface.
– Night feeding: Black-footed albatrosses have better adapted night vision and forage more actively at night. Laysan albatrosses focus their foraging during daylight hours.
– Competition: On shared breeding islands, Laysan albatrosses dominate in aggressively competing for food resources over black-footed.
– Range: Satellite tracking shows Laysan albatrosses focus foraging in a somewhat narrower range around core breeding islands. Black-footed range over a broader area of the North Pacific.
So in summary, the black-footed albatross relies more on squid and active pursuit of prey during both day and night over a broad foraging range. The Laysan focuses on fish and invertebrates during daylight within a narrower range, and is competitively dominant where their habitats overlap.
| Foraging Differences | Black-footed Albatross | Laysan Albatross |
|---|---|---|
| Primary Prey | Squid | Fish, invertebrates |
| Foraging Method | Active pursuit by diving | Sit-and-wait from air |
| Night Feeding | Common | Rare |
| Competition | Dominated by Laysan | Dominates black-footed |
| Range | Broad across North Pacific | Focused around core islands |
Conservation Status
The black-footed albatross and Laysan albatross currently have very different conservation statuses:
– Black-footed albatross: This species is listed as Near Threatened by the IUCN Red List. Their global population is estimated at around 175,000 breeding pairs and appears to be gradually declining. Threats come from habitat degradation, pollution, fisheries bycatch, and disturbances. However, focused conservation efforts on their breeding colonies has helped stabilize populations more recently.
– Laysan albatross: This species is currently listed as Near Threatened with a stable global population estimated around 600,000 individuals. Their numbers rebounded well after the banning of feather hunting in the early 1900s. They face some ongoing threats from fisheries, plastic pollution, habitat loss, and climate change. But current populations appear sustainable if conservation efforts continue.
So in summary, the black-footed albatross has faced steeper declines historically and has a much smaller total population today, placing it at higher risk. Laysan albatross populations are 6-7 times larger and have been more stable in recent decades thanks to conservation measures on their breeding islands. However, both species require continued monitoring and protection.
Migration and Movement
The migration patterns and movements of these two albatross species also show some differences:
– Dispersal: After fledging, juvenile black-footed albatrosses spend 2-5 years drifting across the entire North Pacific before returning to natal colonies. Laysan albatrosses disperse shorter distances and return to colonies more quickly after 1-3 years.
– Migration: Black-footed albatrosses make extensive migrations including down the west coast of North America and along the Japanese coast. Laysan albatrosses are more sedentary and do not venture as far from breeding islands.
– Range: As a result of their longer dispersal and migrations, black-footed albatrosses range over a larger area of the North Pacific basin throughout the year. Laysans concentrate their movements within a narrower range.
– Wintering: During the non-breeding season, some black-footed albatrosses migrate as far south as 20°N latitude near Hawaii. Laysan albatrosses shift north but generally stay within 30°N to 50°N latitude.
So in summary, the black-footed albatross covers a much vaster range through extensive juvenile dispersal and migratory movements. Laysan albatrosses stay closer to their tropical breeding islands year-round.
Taxonomy and Evolution
The black-footed and Laysan albatrosses are considered sibling species that diverged from a common ancestral species during the Pleistocene period:
– Evolutionary relationship: DNA analysis indicates the Laysan albatross is the older species in the genus Phoebastria, diverging around 1.5 million years ago. The black-footed evolved as a sister species around 750,000 years ago.
– Speciation drivers: Their divergence was likely driven by geographic isolation as changing sea levels split ancestral populations. This allowed separate adaptations to evolve.
– Maintained separation: Despite overlapping ranges today, strong site fidelity and philopatry to ancestral nesting colonies appears to maintain genetic and behavioral differences between the species.
– Closely related: These two albatrosses remain each other’s closest relatives and their lineages likely merged at times. But they have been on independent evolutionary trajectories for hundreds of thousands of years.
So in summary, the Laysan and black-footed albatrosses evolved from a common albatross ancestor into distinct, specialized species adapted to different niches and breeding habitats across the North Pacific.
Behavioral Differences
In addition to the breeding, foraging, and migration differences already covered, these two albatross species show some other subtle behavioral distinctions:
– Aggression: Laysan albatrosses tend to be more aggressive both among and between species. Black-footed are subordinate where ranges overlap.
– Swimming: Black-footed albatrosses swim more frequently than Laysans. Their feet have more extensive webbing allowing better propulsion in water.
– Soaring: The long narrow wings of both species allow superb soaring flight. But the black-footed albatross relies more on dynamic soaring techniques.
– Imprinting: Laysan albatrosses have a longer fledgling period and extended parental care compared to black-footed albatrosses.
– Sociality: Black-footed albatrosses forage, feed, and roost together in same-species groups more than Laysans.
– Vocalizations: The calls, grunts, and courtship dances of the two species are distinct with unique vocal repertoires and displays.
So in summary, the Laysan is the more solitary, aggressive species. Black-footed albatrosses spend more time socializing at sea and have more adaptable swimming skills and flight dynamics.
Shared Traits and Behaviors
Despite their differences, the black-footed and Laysan albatrosses share many common traits and behaviors as close relatives occupying similar ecological niches:
– Large size with long narrow wings adapted for soaring flight without flapping across vast ocean distances.
– Use of air currents and wave fronts to achieve remarkable flight efficiency.
– Ability to drink seawater and remove excess salt from nasal glands.
– Keen sense of smell to locate prey and navigation over open ocean out of sight of land.
– Surface feeding by dipping, plunging, and scooping prey while avoiding landing on water.
– Impressive diving ability from flight to pursue prey underwater.
– Courtship rituals like sky-pointing, bill-fencing, and elaborate vocalizations.
– Monogamous pair bonding and shared parental duties at the nesting colony.
– Use of regurgitated stomach oil to feed chicks high-fat diet.
– Slow reproductive maturity and low chick production with high adult survival rates.
– Strong nest fidelity and lifetime attachment to natal breeding colonies.
– Wide pelagic ranges over thousands of miles annually in search of patchy food.
So despite some differences, these two albatrosses share defining traits as members of Diomedeidae adapted as highly efficient soaring seabirds feeding on patchy ocean prey.
Conclusion
In conclusion, the black-footed albatross (Phoebastria nigripes) and Laysan albatross (Phoebastria immutabilis) are highly similar seabird species with ranges centered across the North Pacific Ocean. However, they exhibit a number of subtle but important differences in their appearance, distribution, breeding biology, foraging ecology, movements, behavior, and conservation status. While they face some common threats from fisheries and pollution, current populations of the Laysan albatross are more numerous and stable compared to the declining black-footed albatross. Understanding these kinds of specific differences is important for conservation efforts targeting each species across their ranges and within shared habitats. Going forward, careful monitoring and protective measures focused on their unique nesting colonies and foraging needs will help ensure the long-term survival of both the Laysan and black-footed albatrosses.
