Part I: Background Info on the Pelagic Cormorant

As our boat motored through the swirling turbulent waters of Nakwakto Rapids I looked at the bare cliff faces of Tremble Island located in the middle of the passage. As we approached the rock, gangly black birds with long necks began throwing themselves from the steep walls. As we watched them fly away questions began to form. What were they and why were they here?

Description & Identification

Cormorants are fish eating birds that are found in coastal areas. Cormorants have four webbed toes and are in the Order Suliformes formerly Pelecaniformes. The taxonomy has been reclassified due to genetic and behavioural characteristics (Kennedy 2001). Despite the fact that cormorants are diving birds, their feathers are not water repellent (this may help with buoyancy control). They can often be seen along the shore with their wings spread out to dry. Three different cormorant species call British Columbia home; the Double-crested, Brandt’s and the Pelagic. Interestingly, all three species forage near each other but prefer different substrates. Pelagic Cormorants fish in rocky areas for invertebrates and fish while Brandt’s forage in the water column and Double-crested head for flat sandy bottoms.

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This slender coastal bird is described as having a thin neck and bill. The Pelagic Cormorant is the smallest of the three found in North America. In it’s non breeding plumage, it is all black. Breeding adults can be found sporting a shiny greenish shimmer on the upper wing with a white patch near their legs and a redder face. When seen in flight, this bird’s long neck is straight out (The Cornell Lab of Ornithology).

The pelagic cormorant will probably not be winning any awards for its song. In fact, it is usually silent, what vocalizations it does make have been described as low grunts, pained groaning and hissing. Have a listen!

Distribution

These birds are not migratory and spend most of their time in inshore waters around BC’s coast and in particular, in areas with steep rocky cliff walls. Globally, they are widely distributed from Baja California to the Chukchi Sea and across to Southern China (Atlas of the Breeding Birds of British Columbia).

Habitat & Nesting Locations

It is hard for researchers to survey Pelagic Cormorant nest sites and gain accurate data as colonies can be on remote islands and be very small. Breeding colonies consisting of a few to several hundred pairs have been recorded. To make population studies even harder, these cormorants don’t necessarily use the same location every year. Fun fact, Pelagic Cormorants will use their own feces, guano in bird terms, to solidify their nest to the cliff face as well as provide structural stability. Nest are also made of seaweed, grass, moss and sticks. Cormorants will lay 3-5 eggs and co parent their young. The nestlings are usually able to fly short distances at 35-40. days and leave the nest at 45-55, although it does vary. Parents will continue to care for their young for a few weeks after they initially leave the nest (Audubon 2019).

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You may have noticed in the above images, that the developing young have different looking feathers on their wings. Ornithologists and researchers are able to use the plumage of a bird to determine its age. A “Hatch Year” bird (June-December) will retain more than 90% of its juvenile plumage with almost all of its juvenile flight feathers. At this age, the bird will be medium brownish with ashy or exposed flesh. In its second year (January-May), the juvenile cormorant will begin to develop variable amounts of aquamarine colouration. From May -August, the young bird’s feathers will be very worn and it will have some fresh adult flight feathers (remiges). The exposed skin will also be darker than that of a HY (Filardi 2001). The three images above were taken in August, 2020. Based on the images, how old do you think these birds are?

Conservation

These birds are of low concern. In the 1980’s, the North America population was reported to be over 120, 000 birds with about three- quarters of them located in Alaska (Audubon 2019) It is important to note that in the past 3 decades there has been a decline in breeding populations in coastal areas of Western Queen Charlotte Strait (Carter 2016) as well as Barkley Sound (Carter 2007). The reduction in numbers is attributed to human and eagle disturbance.

Part II: Responses to Marine Traffic and Predation.

Several surveys have shown decreasing populations of Pelagic Cormorants along the Vancouver Island coastline. It is thought that human disturbance as well as increasing eagle populations may be the cause (Clyde 2012). When disturbed during nesting season the parent birds try to protect their nests by flying away from it, or avoiding it. This leads to increased stress, thermal shock in eggs, and in extreme cases, will decrease the breeding success of individuals. If disturbed routinely, seabirds will give up on nesting and wait for another time (Stearns 1976). This is not great for population growth, especially in highly disturbed areas.

A 3 week survey was conducted in Barkley Sound during the height of breeding season to investigate these effects. The researchers observed caves/nest sites from approximately 200m away with binoculars and spotting scopes so as not to disturb the birds. Bird departure and arrival was recorded in 10-minute sample intervals. Vessel and eagle presence within 500m of the site was also recorded. It was found that two of the sites had significantly less cormorant activity when boat traffic or eagles were present (Clyde 2012). Interestingly, a similar study conducted on Double-crested Cormorants in the Strait of Georgia found that they responded to eagle presence but not boat traffic (Giesbrecht 2001).

Conclusion

The Pelagic Cormorant is a slender seabird that calls the British Columbia coastline home. Its long neck and black body are key identifiable features. This bird prefers to make its ness in quiet hard to get to places like the edge of steep cliff faces. Their global population is not of concern however, the numbers of Pelagic Cormorants along the BC coast is seeing a decline possibly due to human disturbance and increased eagle predation. I hope you enjoyed learning about the Pelagic Cormorant and it’s life on the edge.

References

Atlas of The Breeding Birds of British Columbia. Pelagic Cormorant. (Internet): https://birdatlas.bc.ca

Audubon (2019) Guide to North American Birds: Pelagic Cormorant. (Internet): https://www.audubon.org/field-guide/bird/pelagic-cormorant

Carter, H R. McClaren, E L. (2016) Decline of the Pelagic Cormorant in western Queen Charlotte Strait, British Columbia, 1975-2014. Northwestern Naturalist, 97 (1), 24-35.

Carter, H R. Hebert, P N. Clarkson, P V. (2007) Decline of Pelagic Cormorants in Barkley Sound, British Columbia.Wildlife Afield, 4, 3-32.

Clyde, N M. Provencher, J F. Heath, J P. (2012) Responses of Pelagic Cormorants (Phalacrocorax pelagicus) to Marine Traffic and Bald Eagles (Haliaeetus leucocephalus) in Barkley Sound, British Columbia. Northwestern Naturalist, 93(3), 237-240.

Filardi, C. Rohwer, S. (2001) Life history implications of complete and incomplete primary molts in Pelagic Cormorants. The Condor, 103(3), 555-569.

Giesbrecht, T. (2001).The Effect of Bald Eagles and Boat Traffic on Nesting Double-crested Cormorants (Phalacrocorax auritus) In the Strait of Georgia.

Kennedy, M. Gray, R. Spencer, H. (2001) The phylogenetic relationships of the shags and cormorants: Can sequence data resolve a disagreement between behavior and morphology?. Molecular Phylogenetics and Evolution, 17(3), 345-359.

Stearns, S C. (1976) Life-History Tactics: A Review of the Ideas. The Quarterly Reveiw of Biology, 51(1).

The Cornell Lab of Ornithology (2019) All About Birds: Pelagic Cormorant. (Internet):https://www.allaboutbirds.org/guide/Pelagic_Cormorant/overview