Zoological investigations double back-to-school feature

The double-crested cormorant
The double-crested cormorant, Phalacrocorax auritus, is a large, fish-eating waterfowl between 70 to 90 cm long with a wingspan of almost 1.22 m. They are found in Manitoba and throughout the Great Lakes region. They are one of the birds most frequently rescued by the Prairie Wildlife Rehabilitation Centre, or PWRC (see the Science feature article). P. auritus spends its winters in the Gulf of Mexico, flying north to breed during our balmy Manitoba summers. They nest in colonies and incubate by wrapping their webbed feet around the eggs.
Most birds incubate eggs by ruffling their feathers around them and developing a brood patch, a featherless area where blood vessels close to the skin’s surface provide warmth by bringing arterial blood into contact with the eggs. They often incorporate garbage and beach junk into their large nests, including parts of dead birds!

Not the smartest of birds, P. auritus will sometimes mistake large pebbles for eggs and tries its darndest to hatch them! Those nesting in full sun help keep their chicks hydrated by carrying water in their bills to give to the young, which often leave their nest to hang out in a sort of cormorant daycare called a creche, returning to the parent nest at feeding time.

Numbers of P. auritus declined severely throughout the 1950s to the 1970s as a result of high levels of environmental contaminants such as DDE that were responsible for the thinning of eggshells in these and other bird species but, you’ll be glad to know, their numbers have since rebounded marvelously and the cormorants no long appear to be in any danger from population declines.

Also of note according to Lisa Tretiak, board member and founder of the PWRC, young double-crested cormorants are very, very mean and not at all afraid to use their large, hooked bills in combat with would-be human rescuers! For more information on the wacky behaviour of rescued cormorants, check out this link to the PWRC blog: http://pwrc.wordpress.com/2010/07/21/double-trouble/

The Common Nighthawk
The common nighthawk, Cordeiles minor, is not a hawk but a member of the nightjar family, which includes other nocturnal birds such as whippoorwills, frogmouths and oilbirds. In addition to having really cool names, they refuse to build a nest but instead lay eggs straight on the ground, or on city rooftops, without even bothering to conceal them. Perhaps as a defense against this shoddy parental care, nestling nighthawks are able to fly as early as 18 days after hatching and can capture insects within 25 to 30 days. Nighthawks have large mouths lined with sensitive bristles to aid them in catching insect prey during cool-looking aerial dives. They have a reflective structure in their eye called the tapetum lucidum — the same structure responsible for making nocturnal mammals’ eyes, like your cat, glow when a light is shined at them — that improves vision in low-light conditions. They are about 23 cm long with a wingspan of around 51 cm, and spend their winters in South America unlike the rest of us.

Common nighthawks are also brought to the attention of the PWRC rather frequently, but they are often uninjured. The common nighthawk undergoes a daily period of inactivity called torpor, in which the body temperature and metabolism are reduced to conserve energy.
Many a concerned naturalist has phoned the PWRC thinking these birds are in need of assistance when really, they are just resting up for an evening of insect massacre! C. minor populations have been in decline, most likely due to the combination of heavy insecticide usage, habitat destruction and increased numbers of predators such as cats, skunks, raccoons and crows. They are currently listed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as threatened, and are a species of special concern under Ontario’s Endangered Species Act as of 2007.