The next time you spot an eagle perched high in a tree on the North Shore, if you have a camera be sure to take a photo. These are magnificent birds. The North Shore of Burrard Inlet is ideal feeding habitat for Bald eagles. However due to development along the shoreline they are losing their nest trees and their breeding future did not look good. When retired Biologist David Cook heard about the BCIT Rivers Institute Ecological Restoration programme for pocket estuaries along the shoreline of Burrard Inlet he realized that eagles should be part of that upgrade. This is because Bald eagles are a necessary top predator in estuarine habitats. They help to maintain the health of such habitats by removing sick and dead birds and other wildlife.
Working with BCIT, eagle expert David Hancock and other agencies such as Port Vancouver and First Nations he was able to suggest a number of sites for artificial nest sites. This involved defining the feeding range of existing nesting pairs and then defining suitable feeding areas where no nests existed because of a lack of suitable nest trees. The task then was to construct nests in trees or on poles that hopefully the eagles would accept. Four artificial nest sites were constructed in 2013 and 2014 with one presently claimed by a pair of eagles.
While nest site locations are decreasing, the North American eagle population is increasing and surveys at Brackendale and many other locations attest to that. Nest sites on the North Shore between Deep Cove and Horseshoe Bay are few and had been decreasing as suitable trees were removed due to development along the foreshore of Burrard Inlet (both inner and outer harbours and both north and south shores) due to Port and residential development. The feeding habitat of Burrard Inlet is rich and can support many more nesting eagles than it does particularly with the present estuarine restorations.
So nest sites must be constructed to compensate for loss of sites. Natural sites that the eagles prefer in order of preference are mature to old-growth Douglas-fir, mature black cottonwoods, other mature conifer species such as Sitka spruce and western hemlock and less mature conifers that have lost their tops due to storms or cutting so that there is a fork created suitable for cradling the nest.
The principal requirements needed by the eagles are that the tree has branches strong enough to take the weight of the nest and that the nest site be close to a feeding area such as an estuary, mudflat, productive shoreline, or a grain elevator where there are pigeons e. There are certain folks on the North Shore who are working to improve the breeding success of Bald eagles. You can see their work – and sometimes eagles – at several sites along the shoreline where the eagles may be nesting.
Bald eagles are known as “sea eagles” because their preferred feeding areas are estuaries and shorelines as compared to their cousins the Golden Eagle, which are found in the interior of the continent. Bald Eagles are a top predator in the food chain, feeding on injured or dead birds, other birds, rodents and small creatures, and feasting on salmon in season. They prefer to “perch hunt,” sitting high in certain types of trees (such trees will have a wide outlook or are trees that are emergent above the surrounding forest canopy) and watching the sea and ground with their great eyesight. They are not migratory, but will often fly great distances in search of food. Bald Eagles will congregate during salmon season in huge numbers in places like Brackendale, the Harrison River, and Indian Arm.
On the North Shore waterfront there is one site where eagles may be easily observed and that is the constructed platform nest at the Mackay Creek estuary, easily seen from the Spirit Trail. There are two “platform nests,” so called because they were artificially built and installed high in trees and two “pole nests.” The other platform is in Cates Park. The pole nests can be found at the mouth of the Seymour River and another near a grain elevator east of Lonsdale Quay. One of the pole nests was constructed to replace a nest tree removed by the Port for placement of the Low Level Road near the grain terminals in North Vancouver.
David Cook, a retired biologist, is the man chiefly responsible, along with the Fraser Valley’s eagle expert David Hancock, for the fight to save North Shore eagles. Cook has written a lot about our eagles and leads tours. In one of his many articles, he explains that the North Vancouver shoreline historically would have been lined with great trees offering many eagle nesting opportunities. Unfortunately most of the shoreline trees have been replaced by docks, terminals and cranes, with few places offering nesting opportunities along the shoreline. Many suitable nest trees have been removed for residential views most notably in West Vancouver.
No matter where they nest, eagles face significant challenges. Surprisingly, one of their main threats to successful nesting , aside from mankind, are crows and seagulls. Because seagulls and crows compete for the same foods and the same feeding habitats, they will harass eagles, kill the chicks or consume the eggs if they get the chance. They can also hinder nest building. Only two or three eggs are laid in late winter, and after 32 days they will hatch. It’s lucky if two hatch and likely one of those two won’t survive. One adult eagle must always guard the nestling while the other hunts for food.
Cook’s interest in Bald Eagles began in 2000 and each year he monitors 29 Bald eagle nest sites on the North Shore to determine whether they have been active and if so how many fledged young were produced. In 15 years of monitoring these nests, an average of 6 nests per year have been active with an average of three young successfully fledged. These are not good figures. However with the estuarine upgrades and the construction of new nests, these results should improve. David has been a strong advocate for the old-growth (old-growth is hyphenated) trees and flora of Mosquito Creek and other old-growth forest areas on the North Shore and has led many field trips into the watershed. To find out when his next trip is scheduled, or to sign up for his newsletter, email him at firstname.lastname@example.org.
Photos credit: David Cook and Trevor Kelley