Cassin’s Casualties

I usually find interesting things washed up at the high tide line along Wickaninnish Beach in Pacific Rim National Park Reserve—fresh bull kelp is common, as are various types of shellfish and moulted dungeous crab shells. Sometimes the odd sand lance silvers in the sand, and once I found a dead seal. Birds are much more rare. A couple of years ago I came upon a tufted puffin beak washed up in the strand line.

This week I was out with a large group of visitors including some very knowledgeable (and fun) folks on a Canadian Wildlife Federation field trip. We were finding the usual things like bull kelp and a few oddities like sea palm. Then Bonnie found a small, dead black and white bird…

Cassin's Auklet (Ptychoramphus aleuticus)
Bonnie holding the Cassin’s Auklet (Ptychoramphus aleuticus) to display the underwings and white belly.

It was obviously an alcid of some sort based on the body shape and bill; later we conclusively identified it as a Cassin’s auklet (Ptychoramphus aleuticus). Initially, we thought it might have been something very unusual (there’s always a bit of “wishful thinking” amongst birders when something strange is found), but it turns out seeing a Cassin’s up close is rare enough. These small birds are pelagic in nature, spending most of their lives well off shore feeding on crustaceans like krill, copepods, and euphausids as well as larval and juvenile fish depending on the season. Cassin’s auklets only come to shore during breeding season. The bird was beautiful even in death and a decision was made to bring it back to the Kwisitis Visitor Centre to confirm the identification with Parks Canada’s resident seabird expert. A second bird was found on the way back, but it was much worse for wear.

Cassin's Auklet (Ptychoramphus aleuticus) Foot
The blue/grey foot of a Cassin’s Auklet (Ptychoramphus aleuticus). The hole in the webbing may be caused by ticks in the nest burrow.

Cassin’s auklets are small, stocky dark seabirds with a white underbelly. Diagnostic field marks include white crescents over/under eyes, a pale area at base of bill, and distinctive blue/grey feet (not visible while the birds are on the surface of the ocean).

While the Cassin’s auklet is common in BC (around 4 million individuals) the bird is rarely seen from land. It is a burrow nester and the largest colony in British Columbia is on remote Triangle Island off the north west tip of Vancouver Island. 75% of the global population nests in British Columbia, 50% of those birds nest on Triangle Island. Burrows are either reused or dug every breeding season which begins at the end of March. The rest of the year it spends at sea.

Each year, the female lays a single large egg which represents 16% of the bird’s body mass. Once the chick hatches, it is fed for 40 nights. The parents forage during the day and return to the burrow in the darkness of evening carrying a “soup” of fish and crustaceans in a “gular” pouch. Cassin auklet burrows can be identified by purple splashes of guano (remains of crustaceans they feed on) at the entrance of the burrows. At this time of year, the chicks have fledged and both adults and juveniles have left the breeding colonies and are feeding on the open ocean.

Cassin's Auklet (Ptychoramphus aleuticus)
Wings and belly of a Cassin’s Auklet (Ptychoramphus aleuticus).

How did these birds end up dead on Wickaninnish Beach? Some hypotheses can be suggested. It is possible that it was unable to find enough to eat and starved to death. While overall numbers continue to be strong, the breeding population on Triangle Island seems to be declining. Studies indicate that this may be linked to climate change, ocean acidification, and warming ocean temperatures, which impacts the population of crustaceans on which they can feed. With the increased amount of small bits of plastic floating in the ocean, I suppose that it could also be possible that it was feeding on that instead of natural prey. Because Cassin’s auklets are pursuit divers that use their wings underwater like flippers to catch their prey, it is also possible that the dead bird could have been entangled in some sort of fishing gear and drowned. It will be interesting to see if a definitive cause of death can be determined.

Cassin's Auklet (Ptychoramphus aleuticus)
Side profile of the Cassin’s Auklet (Ptychoramphus aleuticus) showing the white crescents below and above the eye and the pale spot on the lower bill.

On the breeding colonies, Cassin’s auklets are vulnerable to introduced predators like rats, and racoons (Haida Gwaii) and other native predatory mammals like mink. Disturbance by humans can crush nest burrows and/or cause the adult birds to abandon the nest. Visitation can also damage fragile natural vegetation, increasing the risk of erosion during heavy winter rain. Oil spills can negatively impact the birds. At night, the lights of boats, industrial activity like oil drilling platforms, and even campfires can attract the birds. There are documented accounts of the Haida using beach fires to capture Cassin’s auklets.

Cassin’s Auklets are one of the most successful species in Canada. Vigorous efforts to prevent oil spills, control introduced pests, and instill common sense in visitors to nesting areas are required to ensure that the birds remain abundant and productive.

– Hinterland Who’s Who—Cassin’s Auklet

Death is a natural part of the cycle of life here on the west coast of Vancouver Island—that’s something that you quickly realize as you walk the strand lines along the beautiful beaches in Pacific Rim National Park. Sometimes that death gives you a gift of being able to see part of the larger ecosystem and an opportunity to think beyond the circle of our own lives.

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