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The black Guillemot and the pigeon Guillemot are two similar-looking seabird species that belong to the alcid family. The main differences between them are:
- Appearance – Black Guillemots are entirely black with white wing patches in summer. Pigeon Guillemots have a black head, wings and back, with a white breast and belly.
- Range – Black Guillemots are found along coasts of the North Atlantic and Arctic Oceans. Pigeon Guillemots are found along the North Pacific coast.
- Breeding – Black Guillemots nest in loose colonies in rocky crevices and caves. Pigeon Guillemots nest in solitary pairs in rock crevices and burrows.
- Diet – Both species feed mainly on fish and invertebrates, but Black Guillemots take more fish compared to Pigeon Guillemots.
- Conservation status – The Black Guillemot has a stable population. The Pigeon Guillemot is nearing threatened status due to declining numbers.
In summary, these two auk species overlap in appearance and habits, but can be distinguished by their geographic ranges, specific breeding behaviors, diets, and conservation status. The Pigeon Guillemot’s numbers are decreasing, while the Black Guillemot is more stable.
The black Guillemot (Cepphus grylle) and the pigeon Guillemot (Cepphus columba) are two similar-looking seabird species that belong to the alcid family. This group, which includes auks, murres and puffins, contains species that spend most of their lives swimming and diving in the northern oceans.
Both black and pigeon Guillemots breed along rocky coastlines and migrate south after nesting season. They overlap in some aspects of appearance, habitat and behavior. However, differences in geographic range, breeding ecology, diet and conservation status make each species unique.
This article will compare and contrast the black Guillemot and pigeon Guillemot. Key points of comparison include physical appearance, breeding range and habits, foraging ecology, population status and major threats each species faces today. Understanding how these two alcids are distinct sheds light on their evolutionary adaptations to specific marine environments.
Appearance and Identification
Black Guillemots and pigeon Guillemots share some physical similarities typical of alcids, yet can be told apart by their plumage.
Black Guillemot
The black Guillemot is approximately 28-35 cm long with a 50-60 cm wingspan. Its defining feature is its dark black plumage during the breeding season. Its thin pointed bill is black.
In winter, its plumage remains black but with white mottling on the wings and head. By summer, its wings transform into solid black with striking white wing patches. Its feet are bright red with black webbing.
Juvenile black Guillemots have variable amounts of white mottling on their bodies. Their bills range from pale grey to black.
Pigeon Guillemot
The pigeon Guillemot measures 28-33 cm long with a 55-60 cm wingspan. True to its name, it has a pigeon-like appearance.
Its head, wings and back are black, while its underparts are solid white. Its thick bill is red with a black tip. Its legs are bright red.
In winter, its white underparts gain diffuse grey mottling. Juveniles are similarly mottled grey and black, gaining more white feathers as they mature.
| Black Guillemot | Pigeon Guillemot |
|---|---|
| Solid black plumage with striking white wing patches in summer | Black upperparts and white underparts |
| Thin pointed all-black bill | Thick red bill with black tip |
| Bright red feet | Bright red legs |
Overall, the black Guillemot has a more uniformly dark appearance compared to the two-toned pigeon Guillemot. However, both species undergo seasonal changes to their plumage and soft parts that aids identification.
Geographic Range and Habitat
The black and pigeon Guillemots have distinct breeding and nonbreeding distributions tied to their preferred marine habitats.
Black Guillemot Range
The black Guillemot is found along coasts of the north Atlantic and Arctic Oceans. Its breeding range extends from northern Europe across Siberia, Alaska and northern Canada. It winters further south to New England, the UK and the Mediterranean.
Its habitat is rocky shorelines, islands and sea cliffs. It readily nests close to human settlements when suitable concrete or erosion control structures are available.
Pigeon Guillemot Range
The pigeon Guillemot occupies the north Pacific region. It breeds along the Pacific coast of Russia east to Alaska, and south to California. It winters south to Japan and California.
Like the black Guillemot, it sticks to rocky coasts and islands for nesting and shelter. It is more averse to human disturbed sites than its Atlantic relative.
| Black Guillemot | Pigeon Guillemot |
|---|---|
| North Atlantic and Arctic Ocean coasts | North Pacific Ocean coasts |
| Breeds across northern Europe, Siberia, Alaska and Canada | Breeds along Pacific coast of Russia to Alaska, south to California |
| Winters south to New England, UK and Mediterranean | Winters south to Japan and California |
| Rocky shorelines, islands, sea cliffs | Rocky coasts and islands |
| Nests readily in human structures | Less tolerant of human disturbance |
In summary, the black Guillemot occupies the north Atlantic while the pigeon Guillemot is a north Pacific species. Their geographic ranges don’t overlap, making identification straightforward based on location alone.
Breeding Ecology
The breeding ecology of black and pigeon Guillemots differs in their nesting habits, site preferences, breeding plumage and mating systems.
Black Guillemot Breeding
The black Guillemot nests in loose colonies, especially where ample crevices are available in rock faces, jetties and breakwaters. It breeds from May to September depending on latitude.
Both males and females gain bold white wing patches during the breeding season. They defend small breeding territories but nest in close proximity at colonies.
Nests consist of scrapes lined with pebbles, shells and seaweed. Eggs are pale blue-green with brown, grey or black mottling for camouflage. Parents take turns incubating the 2-4 eggs for around 4 weeks.
Chicks fledge at 3-4 weeks, able to swim and dive competently. Parents continue to feed and tend to them until independence. Most mature and begin breeding at 2-3 years old.
Pigeon Guillemot Breeding
In contrast, the pigeon Guillemot nests in solitary pairs scattered along the coastline. It breeds from May to August depending on latitude.
It does not develop alternate plumage for breeding. Mated pairs return to and defend the same nest site annually.
Nests are hidden crevices, burrows and caves in cliffs, rocks or underdriftwood. Eggs are equally well-camouflaged. Both parents incubate the 2-3 eggs for 4-5 weeks.
Chicks fledge at 4-5 weeks but continue to be fed by parents away from the nest. Birds first breed at 3-4 years old. Some pairs exhibit long-term pair bonding for multiple seasons.
| Black Guillemot | Pigeon Guillemot |
|---|---|
| Loose breeding colonies | Solitary territorial pairs |
| Gains white wing patches for breeding | No seasonal plumage change |
| 2-4 eggs, incubation 4 weeks | 2-3 eggs, incubation 4-5 weeks |
| Fledge at 3-4 weeks | Fledge at 4-5 weeks |
| First breed at 2-3 years old | First breed at 3-4 years old |
In summary, the black Guillemot exhibits a more colonial, synchronous breeding strategy compared to the solitary pigeon Guillemot. However, both demonstrate strong nest site fidelity and long-term parental care.
Diet and Feeding
The diets of black and pigeon Guillemots consist of similar marine prey, but in differing proportions unique to each species.
Black Guillemot Diet
The black Guillemot feeds mainly on fish like capelin, sand lance, cod and sculpin. It swallows most fish whole underwater.
It also takes shrimp, crabs, polychaete worms, squid and other invertebrates in smaller quantities, mainly during winter when fish migrate away from shore.
They forage relatively close to shore in shallow, coastal waters less than 30m deep. Most feeding dives last 30-60 seconds. Their diet varies depending on locally abundant food sources.
Pigeon Guillemot Diet
Like the black Guillemot, the pigeon Guillemot feeds on fish and invertebrates. However, the proportions differ – it takes more crustaceans like krill, amphipods and crabs and fewer fish overall.
Small fish like gunnels and pricklebacks are still important prey. But the pigeon Guillemot relies more on krill, shrimp and other small crustaceans, especially to feed chicks.
They forage in both shallow coastal areas and deeper offshore waters. Dives last 1-2 minutes to depths up to 30m when searching for fish. Their diet can shift seasonally with prey availability.
| Black Guillemot | Pigeon Guillemot |
|---|---|
| More fish like capelin, sand lance, cod | More krill, amphipods, small crustaceans |
| Smaller proportion of invertebrates | Greater proportion of invertebrates |
| Forages in shallow coastal sites < 30m | Forages from coastal to offshore sites |
| Dives 30-60 seconds | Dives up to 2 minutes |
In essence, the black Guillemot depends more heavily on fish while the pigeon Guillemot takes more invertebrates like crustaceans. But both exhibit flexibility in their foraging strategies depending on locally and seasonally available prey.
Population and Conservation Status
The global population and conservation outlook differs significantly between the black Guillemot and pigeon Guillemot currently.
Black Guillemot Status
The global population of the black Guillemot is estimated at 1.5 to 3 million mature adults. Numbers appear to be stable overall, though some regional declines have occurred.
It is listed as a species of Least Concern by the IUCN. Its ability to nest on artificial coastal structures has allowed populations to thrive.
Current threats include oil spills, extreme weather, human disturbance and competition from expanding Common Murre populations in parts of its range. But none are causing severe declines presently.
Pigeon Guillemot Status
The pigeon Guillemot has a global population of around 200,000 birds. However, numbers are believed to be decreasing, especially in the southern parts of its range.
Habitat loss, oil spills, overfishing, human disturbance and introduced predators are contributing to declines. The IUCN lists it as Near Threatened.
Conservation efforts are underway to protect breeding sites and limit disturbance. But population trends need careful monitoring in case further intervention is needed.
| Black Guillemot | Pigeon Guillemot |
|---|---|
| Global population 1.5-3 million | Global population ~200,000 |
| Population currently stable | Population declining in parts of range |
| Least Concern on IUCN Red List | Near Threatened on IUCN Red List |
| Main threats: oil spills, storms, interference | Main threats: habitat loss, oil spills, overfishing, predation |
In summary, the pigeon Guillemot has a smaller and declining global population, while the black Guillemot remains more widespread and stable. Targeted conservation action may be needed for the pigeon Guillemot in the future.
Conclusion
In conclusion, the black Guillemot and pigeon Guillemot exhibit similarities but can be distinguished by their appearances, geographic ranges, breeding ecology, diets and conservation statuses.
Key differences include the pigeon Guillemot’s two-tone plumage, solitary nesting habits, greater reliance on invertebrates for food and decreasing population trends in parts of its Pacific range. Meanwhile, the black Guillemot remains a ubiquitous and resilient resident along northern Atlantic coasts.
Understanding how these two species are unique, despite some overlapping characteristics, helps shed light on their evolutionary adaptation to the ecological constraints of their respective marine environments in the northern hemisphere.
