Akpa • Thick-billed Murre

The TBMU is one of the most numerous and widespread seabird species found in the Canadian Arctic. There are TBMU colonies in the low, mid and high-Arctic, east from northern Quebec and west to the Northwest Territories. Small TBMU colonies can also be found in BC and Atlantic Canada but more than 95% of the Canadian populations reside in the Arctic colonies. TBMU start to return to their breeding colonies each summer at age 2 but do not begin breeding until they are approximately 5 years old. After mating on the cliffs the female lays an egg 20 days later. The egg is pear shaped which helps prevent it from rolling off the small steep ledges where the TBMU breed. The parents take turns incubating the egg for 30 days. One sits on the egg and keeps it warm while the other returns to the sea to forage for fish. In some years when the sea ice breaks up late this means that the adults have to fly a long way before they can reach open water to where they can get access to the fish and zooplankton they need. Once the chick has hatched the parents become very busy. At first the chicks are small and do not move around very much but soon they become very vocal and active. Now one parent must stay and keep the chick warm and dry while the other parent feeds, but they must not only feed for themselves they must return to the colony with food for the chick to eat. Along the edges of sea ice the TBMU feed on small Arctic cod which is a big meal for a sea bird. After 14 to 22 days on the cliffs the chicks are finally large enough to make the jump down to the sea. The new young birds are not yet big enough to fly so they must jump off the cliffs and glide down to the water. As the chicks get older the fathers start to hang around the cliffs more and more as it is the male parent that leaves the colony with the chick. The dads protect the chick from other birds as it makes its way to the cliffs and follows it down to the sea. Once on the water the father and chick start to head south. Feeding the chick on the water is much easier as the parent does not have to utilize energy to return to the colony, but the pairs must keep moving steadily south in order to leave the Arctic waters before the sea ice fully returns. Sea ice is both needed and can be disastrous for the TBMU. The sea ice is where the Arctic cod can be found, which is the main prey item at many TBMU colonies. The chicks rely on their parents to bring back these fatty fish for them to grow. In low Arctic areas where sea ice extent is receding earlier each year the parents have started to bring in other species of prey. Some are eaten by the chicks like capelin, others like the Northern poacher fish, which is quite rigid and bony, are left on the cliffs more often than not by the chicks who refuse to eat them. But too much sea ice means the adults cannot find reliable food resources close enough to the colony to return each day with food for the chicks. When this happens the TBMU do not raise any chicks. As a result sea ice plays an important role in seabird biology in the Arctic ecosystem and understanding these interactions is key to understanding how changes will impact seabirds in the area.

Photo Credit: Thick-billed Murres (Uria lomvia) in Alaska refuge by Art Sowls (USFWS), 2010. https://commons.wikimedia.org/wiki/File:Thick-billed_Murres_in_Alaska_refuge.jpg. Licenced with Public Domain.