Bald Eagles around Cobourg Harbour

Nature Notes for February 27, 2015

Where are the gulls? Usually when Cobourg Harbour is frozen, this is a favourite place for roosting gulls. This winter, there have been very few. It is not the cold that is making them scarce, but the presence of at least two Bald Eagles.

One adult and one juvenile Bald Eagle are being seen regularly around the harbour. Bald Eagles take four years to get their full white head and tail. They don’t breed until then. The dark body of these adults is actually a very dark brown. The juvenile was hatched last year. Its plumage is mostly brown with white blotches. Young Bald Eagles are frequently mistaken for Golden Eagles. (The latter occur in Northumberland County only in migration, and rarely in winter.)

Two Bald Eagles have been frequenting Cobourg Harbour.

photo © Rob Lonsberry Photography

In the late 1800s and early 1900s, there was, in some places a bounty on Bald Eagles. Fishermen on the west coast thought that the eagles were eating spawning salmon. They didn’t pay attention to the fact that the eagles were eating mostly dead and dying fish that had already spawned.

In that era, too, egg collecting was a common activity of those who studied birds. Fortunately for the birds, there is now recognition that this threatens the survival of some birds, particularly large birds such as eagles that reproduce slowly.

Despite these activities and despite often being shot, Bald Eagles were known to nest in several places in Prince Edward County and at Presqu’ile into the 1930s.

In the middle of the 20^th century, Bald Eagle populations were decimated by the use of pesticides, especially DDT. The buildup of chemicals prevented the birds from reproducing successfully. Since the 1970s, when DDT was banned in North America, Bald Eagle populations have slowly increased.

Eagles need a large undisturbed territory to nest successfully. Human infringement on their habitat has made some eagles abandon long held territories.

Bald Eagles have a very long life span. According to bird banding records, the oldest Bald Eagle reported was 31 years old. They usually only produce one or sometimes two young per year. They don’t breed until they are 5 years old. Since they reproduce slowly, only recently are populations showing an increase from the decline during the years of DDT use.

In the 20 years between the two Ontario Breeding Birdatlases, there was a marked increase in breeding Bald Eagles in southern Ontario. The field work for the second Atlas was done 10 years ago. Locally, the population seems to be on the increase.

Just last weekend, one observer saw 10 eagles on the ice on and near Presqu’ile Bay. The 2014 Port Hope-Cobourg Christmas Bird Count found a record high five Bald Eagles, most along the Lake Ontario shore. This count has recorded at least one Bald Eagle every year since 2007. The Presqu’ile-Brighton Christmas Bird Count has shown a similar increase, with a high count of 8 in 2013.

Rice Lake is also a good area to find Bald Eagles. There have been reports in recent years of them breeding on some of the islands in the lake and in the Trent River.

Although Bald Eagles remain a “Species of Concern” on the Ministry of Natural Resources Species at Risk list, Bald Eagles are one of the more successful conservation stories. Despite past human persecution, human intervention has now helped the species recovery.

The next time you see the gulls flush up in confusion at Cobourg Harbour, look up. You may very well be treated to the sight of a Bald Eagle.