Pulling Numbers Out of Thin Air

Every fall in High Park, you can count on two things. Migrating birds will pass overhead and people will come to watch them do it. The watchers gather on Hawk Hill, a small bump of earth rising just north of Grenadier Restaurant. Although more than 150 different kinds of birds may pass through on their way south, people come to Hawk Hill particularly to watch the raptors.

These meat-eating birds of prey seen from Hawk Hill include Turkey Vultures, Bald Eagles, Golden Eagles, Sharp-shinned Hawks, Cooper’s Hawks, Northern Goshawks Red-shouldered Hawks, Red-tailed Hawks, Broad-winged Hawks, Rough-legged Hawks, American Kestrels, Merlins, Northern Harriers and Peregrine Falcons. While songbirds are hopping and hiding in the bushes, these raptors steal the show, large and steady in the sky, exhibiting their distinctive forms and flight styles.

Take the Cooper’s Hawk for example. These middle-distance flyers have short rounded wings and very long rudder-like tails for maneuvering through woodland canopies at high speed. Their flight style will catch your eye with a flap-flap-glide motion. In contrast, the Red-tailed Hawks with their longer, larger broad rounded wings and short wide tails are built for gliding. You will see just the occasional heavy wing beat from these birds soaring in wide circles overhead.

From September 1 to November 30, an official recorder spends each day on Hawk Hill. Other keen-eyed observers join the recorder with skyward gazes to spot, identify and count the raptors. Along with the data collected by more than 100 other North American Raptor observation sites, the weekly totals recorded at Hawk Hill are reported to the Hawk Migration Association of North America (HMANA). Cornell University is the final destination of all the data.

This important information alerts us to trends and changes in bird populations that signal problems. This very system informed the world in the 1970s of the drastic decline in young eagles and resulted in a ban on the pesticide DDT. While the data collection is official and invaluable, the main attraction to Hawk Hill is pure fun and wonder. Everyone is welcome and many people come to share in the adventure and excitement of tracking the birds on their annual fall migration.

At the Hawk Watch

Karen Yukich

  The following raptor species can be seen during   the fall migration:

• Turkey Vulture Cathartes aura
• Osprey Pandion haliaetus
• Bald Eagle Haliaeetus leucocephalus
• Northern Harrier Circus cyaneus
• Sharp-shinned Hawk Accipiter striatus
• Cooper’s Hawk Accipiter cooperii
• Northern Goshawk Accipiter gentilis
• Red-shouldered Hawk Buteo lineatus
• Broad-winged Hawk Buteo platypterus
• Red-tailed Hawk Buteo jamaicensis
• Rough-legged Hawk Buteo lagopus
• Golden Eagle Aquila chrysaetos
• American Kestrel Falco sparverius
• Merlin Falco columbarius
• Peregrine Falcon Falco peregrinus

Juvenile Bald Eagle

Iain Fleming

Why Do They Leave in the Fall and Return in the Spring?

Migration to a warmer place is all about following the food, not about staying warm. Raptors eat animal protein. When cooler temperatures force these food sources (insects, mammals, reptiles, amphibians) into winter hiding for months of sleeping or eating stored reserves, the raptors must move to new hunting grounds. In their warmer southern haunts, these migrant birds of prey must share food and roosting sites with local resident birds. At that time of year there is enough to go around because both migrant and resident birds are feeding only themselves and not whole broods. However, come spring, the migrants must make the grueling trek back north where they will find plenty of nesting sites to choose from and many newly emerged animals to eat.

Turn Right at the Lake

Some raptors migrate great distances. For example, the Broad-winged Hawk flies more than 100 km a day for two months to cover 7000 km. Consequently, raptors use several strategies to prevent exhaustion. They often wait for a wind from the northwest. If the wind is blowing at the right angle, the extra push saves a lot of energy. They also take advantage of winds that blow against rising landforms, like the elevated southern edge of the park by Colborne Lodge. These vertical barriers force the air to ride up along the ridge and without much flapping, raptors are able to ride the updrafts like surfers ride waves.

Another labour-saving tactic is to ride thermals. Where land surfaces heat up in the sun, air rises over these warmer spots and offers raptors another free ride. They cover distance by soaring from one thermal to the next. There are no rising thermals over water and it is too risky for these birds to fly where they will have to expend energy by flapping their wings. If they run out of energy over water, they will drown. That is why many of the raptors fly south until they encounter Lake Ontario where they do a collective “whoa” right over High Park before turning right to follow the shoreline in a westerly direction.

High Park has become a permanent residence for a few hawks. A family of Red-tailed Hawks and a Cooper’s Hawk are now year-round regulars that have been fondly named by devoted Hawk Hillers. The birds behave like real characters providing great entertainment on Hawk Hill with their circling, calling, soaring, dive-bombing and performances of aerial acrobatics. Perhaps we may see growing numbers of raptors over-wintering or nesting in High Park with the increase in urban food sources such as rats and squirrels at birdfeeders.

The Nightshift on Hawk Hill

There is another migrating bird that attracts people to Hawk Hill. Although its shape somewhat resembles a hawk’s, the Common Nighthawk is not a hawk and is no longer common. Before their population plummeted, the Common Nighthawk used to be much more of a familiar presence in Toronto’s summer skies, but you can still be a witness to their summertime evening spectacle if you’re lucky. During the day, nighthawks are just about invisible, but come dusk, they come out to feed in buoyant flight when lots of flying insects are available for midair snatching. Common Nighthawks put on quite an airshow of swooping loops with buzzing and booming sound effects. In fact, their genus name, Chordeiles, is from Ancient Greek “khoreia” which means “a dance with music.”

Fly Up and Be Counted

Around mid-August, all the Common Nighthawks in North America start their epic long migration to South America, and large numbers of them coming from other summering grounds fly over High Park. That’s when recorders organized by Bird Studies Canada show up for the count. For three weeks, these dedicated volunteers come to Hawk Hill each evening at sunset to record Common Nighthawk sightings. The Bird Studies Canada nighthawk count on Hawk Hill was started in 2013 and continues to get enthusiastic support and participants from the High Park Nature Centre.

These birds would get missed in any of the usual North American daytime bird counts organized to track bird population trends. Common Nighthawks are so impressively camouflaged and motionless during the day that it is difficult to spot them. Yet, they need to be counted! Their numbers have dropped dramatically and they’ve been placed on the “threatened species” list. Data collected between 1968 and 2005 indicates their population in Canada decreased by 80% during that time.

Some reasons for their steep decline may include fewer insects to eat due to climate change and pesticide use, and an increase in nest predators like gulls, crows, raccoons, opossums, dogs and cats. Keeping count of the nighthawks could help to identify certain trends that may lead to successful recovery of this species.

Contributed by: Kathleen Keefe

   Common Nighthawk

   Don Faulkner, courtesy BSC

See also:

- High Park Hawk Watch

- Nighthawk Watch

- Red-tailed Hawk