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 10o 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.
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, 3rd ed. 1999.