Sorting Out Swallows               Index

by Barb Glass               (Reprinted with permission - Prairie Smoke Vol.2-4 Spring 2005)

 About 89 swallow species exist worldwide in the Family Hirundinidae. The only continent lacking swallows is Antarctica.  Africa and South America have the greatest diversity of species.  In North America, there are 9 regularly occurring species and 5 more occur accidentally.  In Central Ontario, there are 6 breeding species of swallows – Purple Martin, Tree Swallow, Bank Swallow, Northern Rough-winged Swallow, Barn Swallow and Cliff Swallow.

Many sayings, songs and proverbs refer to Swallows.  The proverb “One swallow doesn’t make a spring” is attributed to the Greek philosopher Aristotle and dates back to 325 B.C.   Another saying - “Swallow flying high, the weather will be good. Swallow flying low, soon it will rain.” - is scientifically correct.  For the primary diet of the swallow family is flying insects, and in poor weather the insects are lower to the ground, and thus the swallow is too.  Swallows do not return in the spring before there is an abundance of insects to eat, and that usually requires that the temperature be consistently above 10^o C.

Different swallow species employ different feeding strategies. The stronger flying Purple Martins and Cliff Swallows tend to feed at higher altitude and over land on swarming insects.  In breeding season,

Barn Swallows and Rough-winged Swallows usually feed lower down, over fields and water respectively.  They, like Tree Swallows, tend to feed in solitary.  Cliff and Bank Swallows feed gregariously, due to their colonial nesting.

While all swallows are aerial insectivores, their nesting behaviours divide them into two distinct groups: cavity nesters (Purple Martin, Tree, Bank and Rough-winged Swallows) and mud nesters (Barn and Cliff Swallows).

Bank Swallows excavate tunnels in steep sandbanks and nest colonially.  Several hundred nests might be located together.  Locally, these nests may be found in quarries.  The Rough-winged Swallow is a solitary nester that will occupy abandoned kingfisher or Bank Swallow tunnels if available. Increasingly the Rough-winged uses manmade structures such as drainpipes, culverts, crevices in bridges, or holes in the side of buildings.  Tree Swallows and Purple Martins prefer to nest in cavities, such as old woodpecker holes or snags, near water.  Draining swamps and cutting dead trees has reduced the number of potential sites.  Now both these species mainly nest in man-made nesting boxes. 

Tree Swallows are fond of Bluebird boxes.  In eastern North America, the declining Purple Martin nests colonially in white multiple-roomed houses erected especially for them. 

Barn Swallows build simple cup-shaped nests from mud and grass.  They used to build these on cliff ledges or in small trees, but today almost all their nests are in open buildings, or under eaves, bridges or docks.  Several pairs may nest in the same immediate area, but this is not a social grouping like that of the Cliff Swallow.  Cliff Swallows always nest colonially, and may pack dozens to thousands of gourd-shaped mud nests under eaves, bridges or cliff ledges. hese colonies may be reconstructed in a suitable location (such as the Kirkfield Lock) for many decades.

The plumage of males and females is quite similar in most swallow species.  The exception is the Purple Martin.  Adult males are dark glossy purplish-blue, while females and juveniles are gray below.  In flight a male Purple Martin can be distinguished from the similarly sized and coloured starling by its forked tail, longer wings and typical swallow flight pattern of alternating rapid flapping with short glides.  Tree Swallow adults are dark glossy greenish-blue above and white below, appearing more greenish as fall approaches. 

The Bank Swallow is the smallest swallow, with brownish-gray distinctive breast band and back, and white throat, ear patch and under parts.  The similarly coloured Northern Rough-winged Swallow lacks the breast band and the white ear patch.  In flight, Barn Swallow adults are easily identified by their long, deeply forked tails.  These colourful birds have deep blue backs and shoulders, reddish-brown throats and foreheads, and cinnamon under parts.  Even the juvenile has a noticeable fork in its shorter tail. 

Like Barn Swallows, Cliff Swallows have dark chestnut throats, but are readily distinguished by their squarish tail (like a paint brush), buff rump and pale forehead and under parts. These adept aerialists are amusing to watch as they dart about to capture their food.  One of my favourite swallow encounters is watching them swoop after     the insects that are  disturbed when mowing the grass. If you see them over water, observe carefully, as they may drink and bathe on the wing.  After breeding season, you may observe several species together on a wire or a tree snag.  This is a good chance to study the juvenile plumages.

One swallow may not make a spring, but the arrival of spring does mean that the swallows are soon to return.  Enjoy them while you can.

REFERENCES:

Kaufmann, Kenn.  Lives of North American Birds, 1996. Houghton Mifflin 

National Audubon Society.  The Sibley Guide to Bird Life & Behaviour, 2001. Knopf .

National Geographic Society.  Field Guide to the Birds of North America, 3^rd ed.  1999.

The Kirkfield Liftlock        Index

 

The hydraulic liftlock at Kirkfield constructed between 1896 and 1907 is a massive structure with a lift of 49 feet.  It is the second largest hydraulic lift in the world second only to the Peterborough liftlock on the same system with a lift of 65 feet.  Both lifts have chambers 140 feet long, 33 feet wide and a normal water depth of eight feet.  

 

The concept of these two liftlocks was derived from liftlocks built in England, Belgium, and France in the 1870s and 1880s. The Trent Canal Superintending Engineer, Richard B. Rogers felt that due to their geographic locations, both sites would benefit from a lift, as opposed to the conventional lock. Water conservation, cost, and lockage time were all contributing factors. Originally, Rogers envisioned cargo transportation on the Waterway being done by using strings of five to twelve barges towed by a single vessel.

The Kirkfield Liftlock operates as originally constructed except for the addition of new hydraulic and electrical control systems in 1965-66.

The mechanism may be likened to a giant scale consisting of two chambers. When an extra foot of water is added to the upper chamber, and the crossover valves are opened, the heaver chamber over-balances the lower chamber forcing it to rise. Each chamber holds 228,093 gallons of water, weighing 1,700 tons. The weight of the vessels in the chambers is irrelevant, as each vessel, by virtue of its entry, has already displaced its weight in water before the gates were closed.  The chamber stops one foot short of the upper canal level, allowing one foot (144 tons) of water to flow in when the hinged gate is lowered (opened). The chamber is now ready for its next downward journey.  Conversely when a chamber reaches the bottom, the water level in the chamber is one foot above the lower canal level until the gate is opened allowing the water level in the chamber to drop which prepares it for its next lift upward.  The Kirkfield Liftlock is the highest elevation on the canal and boaters are reminded by signs along the canal that they are now traveling downstream and the relative position of the buoys will be reversed.

Bright blue guard gates on either side of the canal are designed as a safety feature to protect the liftlock in case of a sudden surge of water. The gates are shut at night and can be closed to seal off the river even as water rushes through them in case of an emergency.