Cyril Crocker — Raptors at Hawk Cliff
Recap by Michael Frind
Cyril Crocker, a seasoned expert on birds of prey and long-time bird-bander, gave a fascinating
talk on the ecological role and function of hawks, falcons and eagles. He also discussed the
migration patterns and bird-banding findings pertaining to these unique avian species, and
focused on the ongoing research activities taking place at Hawk Cliff. His talk was
complemented by a plethora of intriguing slides and a display of bird-banding equipment.
Cyril began by noting how raptors were, for many years, persecuted as being murderers of
songbirds such as doves and cardinals. The problem was that the average person was unaware of
the role of raptors: to weed out the weak and diseased individuals of the prey population. Such
weeding-out ensures that only the strong and healthy survive to pass on their genes. This means
that that the surviving individuals of the prey population are invariably free of vulnerabilities and
The raptors themselves are weeded out not by other species, but rather by the extreme difficulty
in capturing their prey. For a raptor to successfully capture enough food to survive (and
ultimately, to reproduce), it must be completely free of any mental and physical infirmity. The
end result of this delicate balance of nature is that the gene pools of both the hunter and hunted
populations remain undiluted by poor genetic material.
Hawk Cliff, a picturesque rocky outcrop located on the Lake Erie shoreline west of Long Point,
constitutes a major Great Lakes crossover point for southbound birds of prey. Other popular
crossover points for migrating raptors include Niagara Falls and Point Pelee, as well as Holiday
Beach near Amherstburg. (The term “hawk” is generally taken to include both the Accipiter and
Buteo families, and includes many of the raptors seen in North America.)
The attractiveness of these crossover points to avian migrants results from various factors,
including prevailing winds and minimum-distance considerations. Additionally, songbirds
constitute a major food source for hawks, and so the raptors tend to follow the movements of
songbird populations. Hawks migrate differently from songbirds. They also use very different
flying strategies, and this is a major reason for their choice of the aforementioned crossover
Flying consumes large amounts of energy, and this holds true for all birds. Typical songbirds
have the luxury of being able to land and eat at will, as their food (in most cases, berries, nuts,
earthworms, and so on) is easily obtained anywhere there is land. But hawks cannot do this,
since they must hunt in order to survive. This means that when not engaged in hunting, they
must conserve their energy very carefully. Therefore, hawks must ensure that an energy reserve
adequate for hunting remains available at all times during a seasonal journey, the final
destination of which is Central or South America.
Hawks conserve their energy very efficiently by being experts at soaring. They wait until mid-
morning, when sufficient thermals (pockets of rising air warmed by the sun shining on the
ground) have developed. They catch a thermal, circle around lazily inside it, and ride until they
have reached an altitude at which the air has cooled and the thermal has dissipated. Then they
exit the thermal and glide for as long as possible. They often look for fellow hawks already
gliding on thermals, and join them. At nightfall, the hawks land and rest. On non-sunny days
during migrations, hawks prefer either to rest or to hunt.
Large water bodies, such as the Great Lakes, cool the warm daytime summer air, and thus tend
not to generate thermals. Because thermals are strictly a terrestrial phenomenon, hawks would
be forced to flap furiously in order to cross large bodies of water. By choosing their crossover
points wisely, these birds can minimize their energy expenditures.
Hawks soar at altitudes up to 8000 feet, and thus can be invisible to people equipped with
standard spotting scopes. At Hawk Cliff, the best viewing times occur between September and
December, whenever a northwesterly wind is present. The record single-day count was 108,000
hawks on September 16, 2000.
Bands used for identifying birds of prey come in various sizes. The largest band has a diameter
of one inch, and is suitable for owls and large raptors. For sharp-shinned hawks and kestrels, the
bands are simply butt-ended types, and are crimped on. Typically, once banded, a bird takes a
few minutes to examine and pick at its new piece of aluminum jewellery. Then it accepts the
band’s presence, and carries on. But larger raptors (such as harriers, red-tailed and Cooper’s
hawks, and Peregrine falcons) have beaks that are strong enough to pry off butt-jointed bands,
and so locking-tab-equipped bands must be used. Eagles have even more powerful beaks, and
thus require heavy-duty, riveted-on bands.
The banding procedure entails capturing the bird in a mist net, gently disentangling it from the
net (whilst cradling it gingerly in one’s hands, so as to prevent valiant flapping and potential
wing damage), and placing the bird in a tube made of piping or several metal cans taped
together. This procedure ensures that the bird calms down immediately, and increases safety for
banding staff, as the talons of most raptors are an inch or longer, and are razor-sharp. The
canning method also enables easy weighing of the bird, as well as age determinations.
In Ontario, bird-banding has been in progress since 1968. Fifteen sites in the province are
licensed by the Ministry of Natural Resources and the Canadian Wildlife Service. Data are
collected by the latter organization, and are forwarded to the Patuxent Wildlife Research Centre
in Maryland. Only the bands themselves are provided free of charge; the tools and mist nets
must be purchased at cost.
The purpose of bird-banding is two-fold: to track the migration of birds, and also to track the
year-to-year survival rate. The data gleaned are helpful in determining long-term population
trends, and form the basis for a variety of intensely analytical research projects.
Banding of young birds has shown that 60% of those which leave the nest fail to make it to their
first birthday. Occasionally, small hawks are consumed by larger ones. And, some die from
motor-vehicle crashes and other human causes. The major cause of death of young birds seems
merely to be starvation due to inexperience in hunting and pursuit-type flying.
Cyril noted that a typical hatching-year member of the Accipiter family has straw-coloured eyes,
and vertically-streaked mottled plumage. As the bird ages, its eyes take on a reddish tint, and the
streaking on the breast becomes rusty and horizontal. Meanwhile, the back takes on a slate
colour. Accipiters are considered the true hawks, and they tend to hunt in woodlands. Examples
are the Goshawk, the sharp-shinned hawk, and the red-tailed hawk. (Goshawks are distinguished
by a black eye-streak.)
Falcons can be thought of as the military fighter jet of the avian world. With their long, slender
wings, they can fly from A to B in the shortest possible time. Falcons are notable in that the
hatching-year birds have the same colouration as the adults. The tail is rusty, and the
subterminals are black. Falcons are the only raptors that are cavity-nesters.
The Marlin is a small (dove-sized), torpedo-shaped falcon, and is native to northern regions.
Peregrine falcons are notable for their ability to dive at an astounding 300 kilometres per hour.
They are also unique in that they commonly fly over water, and have been found at 500
kilometres from shore. Peregrines have recovered well from the DDT-induced population
declines, although extensive transplantation projects were required.
Hawk Cliff is a good venue for observation of a wide variety of raptors. The Buteos are the
aforementioned masters of soaring. Harriers, with their light-patch-containing plumage, are best
searched for by sound. Also common are Osprey (low, gull-like flight), turkey vultures
(common in large hawk groupings, known as kettles), as well as assorted kestrels, owls, bats,
kingbirds, shrikes, and woodpeckers.
Bald eagles are rarely seen, perhaps only once annually at Hawk Cliff. Most of the eagles
observed there are hatching-year specimens. Their majestic seven-foot wingspan makes these
the largest raptors by a significant margin. Golden eagles are rarer still, and they enjoy colder
climates such as Labrador. The Golden eagle has feathered legs, and is well prepared for bone-
Sincere thanks to Cyril Crocker for providing us with a profound understanding of the beauty
and purpose of raptorial species.