| Rhinoceros auklet | |
|---|---|
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| Adult, Japan | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Alcidae |
| Genus: | Cerorhinca |
| Species: | C. monocerata |
| Binomial name | |
| Cerorhinca monocerata (Pallas, 1811) | |
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Therhinoceros auklet (Cerorhinca monocerata) is aseabird and a close relative of thepuffins. It is the only extant species of thegenusCerorhinca. Given its close relationship with the puffins, the common namerhinoceros puffin has been proposed for the species.[2]
It ranges widely across the North Pacific, feeding on small fish and nesting incolonies. Its name is derived from a horn-like extension of the beak (the anatomic term for this extension is therhamphotheca). This horn is only present in breeding adults, and like the elaborate sheath on the bill of puffins is shed every year. This horn also possessesfluorescent properties, which is likely involved in reproductive signalling.[3]
The rhinoceros auklet (also known as therhino auklet,horn-billed puffin, orunicorn puffin), is a medium-sizedauk with a large, strong, orange/brown bill (with the 'horn' protruding from it). Theplumage is dark on top and paler below; breeding adults (both male and female) possess white plumes above the eyes and behind the bill. Males are slightly larger than females (about 10% in mass).[citation needed]
The rhinoceros auklet is a North Pacificauk that breeds from California (theChannel Islands) to theAleutian Islands inAlaska in North America; andHokkaidō andHonshū, Japan, as well as theKorean Peninsula andSakhalin Island in Asia. It winters both in offshore and inshore waters, exhibiting somemigration. Between October and April, migration of a large number occurs on pelagic California waters, most coming from breeding colonies north of California. Auks that reside off the California coast remain in their areas.[4]
Breeding occurs in the early summer months, ranging from May to June. The auklet nests in burrows dug into the soil, or in natural caves and cavities between 1 and 5 m deep. It prefers nesting sites on slight inclines to aid take-off, as it is a poor flier. A single egg is incubated by both parents for 30–35 days. The semiprecocial chick is then fed each night with a bill full of fish (in the manner of puffins) for 35–45 days. Thisnocturnal behaviour is believed to be a response to predation andkleptoparasitism bygulls.[4][5]
Rhinoceros auklets are monogamous, and although they migrate across similar areas during the non-breeding season, pair-mates migrate separately. However, they do synchronize their foraging activity once they return to the colony during the pre-laying period.[6]
At sea, rhinoceros auklets feed on fish, with somekrill andsquid taken also. They feed inshore during the breeding season in the midwater. To catch their prey, they dive as deep as 57 meters (187 ft) for as long as 148 seconds.[7]
Diet studies of nesting rhinoceros auklets show that their diet is variable depending on the location of the bird's nest. At one island located near theSalish Sea off of the Washington coast, auklets feed mainly onsand lance, while at a separate island also off of the Washington coast, auklets feed onanchovy andsmelt.[8]
The genusCerorhinca evolved in the North Pacific, apparently in the mid-lateMiocene. Although today only one species remains, it used to be much more diverse, both in number of species and in distribution. Fossils have been found as far south asBaja California. The first record of the clade from the Atlantic Ocean was reported by Smith et al. (2007) and suggests that the biogeographic history ofCerorhinca is more complex than previously thought.[9] Known prehistoric species are:
Since rhinoceros auklets are monogamous and highly social, the species depend heavily on physical characteristics of the other species in order to choose a lifetime mate.[11] The prominent horn on the bill of breeding rhinoceros auklet is one evolutionary byproduct of this behavior. The bill has fluorescent characteristics when viewed under ultraviolet light. Several bird species are able to detect cues through UV light,[12] which supports the claim that this fluorescence is also meant for breeding purposes. While the upper and lower mandible give off fluorescence as well, this phenomenon is most prominent in the horn. There is no evidence for disparity of fluorescence between sexes, however, the amount of fluorescence does vary between individual auks.[3]
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