By: Dr. Annamarie Hatcher
What is happening in the Bras d’Or Lake Biosphere in this early spring period?
In the Mi’kmaw calendar, April is Pnatmuiku’s or “birds laying eggs time” and one of our most iconic biosphere birds is settling down in the nest with freshly laid eggs at this time of year. The bald eagle (in Mi’kmaw “Kitpu”) plays an important role in the ecological balance of the biosphere and is a valued resident. Kitpu is sacred in Mi’kmaw culture because its’ accomplished flying and soaring abilities mean that it can carry messages to and from the Creator.
Not only are bald eagles valued residents, the Bras d’Or Lake Biosphere is very important for the whole Northeastern North American bald eagle population. According to the Department of Natural Resources (DNR), Nova Scotia has the highest concentration of breeding bald eagles in northeastern North America and most Nova Scotian eagle nests are found on Cape Breton Island, concentrated around the Bras d’Or estuary. It is an ideal habitat for this valued resident and a significant area for the species.
So, what exactly is ideal habitat for breeding bald eagles? According to the DNR, bald eagles require relatively large areas of suitable habitat in mixed or hardwood forest for breeding. Ideal breeding habitat for a nesting couple is around the size of 480 football fields or more, and includes large rivers, lakes or estuaries (such as the Bras d’Or) in a mature forest. For you hikers, I’ll bet that many areas in the biosphere come to mind.
Because this species is so important to us, we have spent a lot of time determining what the essential components of that ideal habitat are. To manage habitat to encourage breeding eagles, DNR suggests that forestry workers preserve eight to 12 mature, solid living trees in a 260-hectare (640-acre) area within 400 metres of a lake or river. In this essential breeding habitat, eagles also require dead, partially dead, or living perch trees, that project above the rest of the trees within 400 metres of each nest site.
In the natural world, all things are connected. Eagles need trees and lots of space. Mi’kmaw Elder Albert Marshall has said that we need to consider more than just the trees when we manage forests. That means in our best practices forestry management strategies, we need to consider eagle breeding habitat. This is particularly important in the Bras d’Or Lake Biosphere Reserve.
In addition to trees, bald eagles need fish. The bald eagle is a member of a global bird group called fish-eagles. They can frequently be seen soaring or perched over water where they swoop down to catch any available fish. They are adept predators, and when fish supplies are lean, I have seen eagles hunt young merganser ducklings who wander too far from their mother.
Last spring, my son had to slow down while driving down Highway #4 near Irishvale as an eagle swooped in and left with an adult snowshoe hare gripped in its talons. Carrion is also a dining option. I have watched a family group of three eagles pick clean the carcass of a dead beaver in jig time!
Bald eagles are obvious throughout the biosphere all year. It is one of the known wintering sites in Nova Scotia, providing adequate food during that time. In March and early April, there seems to be a lot of amorous activity between biosphere eagles. Although they form lifelong pairs and mate for about 10 months of the year, female biosphere eagles are fertile for only a two week period around mid-March. This is perfect timing for the hungry, fertile female to take advantage of the annual smelt run in the estuary.
In some areas of the Bras d’Or estuary that are still iced over, eagles can be seen perched on the ice near cracks and holes, waiting for a school of smelt to swim by. These little fish, many of which give up their lives to provide sustenance for the predatory eagles, are on their own desperate run to reproduce. It is an exciting time of year, isn’t it?
So, you know what they say about spring and thoughts of love? As the days get longer at this time, the pituitary glands of the female eagle produce a hormone which causes eggs in the future mother’s ovaries to mature. If her amorous mate is successful, copulation will result in a fertilized egg or two being laid about five to 10 days later and large fledglings leave the nest in August.
These impressive nests are often built near the top of a prominent tree and are used by the same couple year after year, with slight renovations annually until a perfect size and shape is achieved. Apparently, a nesting pair in East Bay has been adding wads of seagrass to soften their nest this year, so I have been told. After the eggs are laid, the female does the bulk of the childcare but both sexes deliver food. Sound familiar?
When talking about the copulation of bald eagles, I have to mention their spectacular courtship display, sometimes called a “death spiral.” The amorous pair soar to a high altitude, lock talons and plummet toward the earth, releasing (hopefully) just before they hit the ground. If you are a regular at Ben Eoin ski hill, you may have witnessed this exciting display from the chair lift. If conditions are right, the pair then fly to a nearby tree and engage in the act that physically transfers mature sperm to the female. This part is not nearly as exciting as the foreplay, lasting only seven to 10 seconds.
The “death spiral” reminds me of the scene at a party when a young man moves onto the dance floor and gives it his all to attract a potential mate. Not as risky but impressive nevertheless.
So, as you are out in the biosphere at this time of year, watch for the eagles and think about the next generation which is just beginning!
Dr. Annamarie Hatcher is a consulting ecologist and a board member of the Bras d’Or Lake Biosphere Reserve Association. Thanks are due to Tuma Young for giving me permission to use the fantastic picture of locked eagles which he took at Ball’s Creek. For more information about the Bras d’Or Lake Biosphere Reserve Association, please visit http://blbra.ca/ or check out our Facebook page.