At the end of April – May, the migration of small songbirds begins in Ontario. By their small size and tinny graceful beaks, they resemble the warblers of the Old World. Warblers of the Old World belong to the Phylloscopus genus and include small insectivorous birds found in Europe, Asia, and Africa. Most of the American small songbird species, occupying similar ecological niches and specializing in insect hunting, are also called “warblers”. However, taxonomists distinguish warblers of the Old and New World. They place the American species in the family Parulidae or New World Wood Warblers. American “wood” warblers are very different from “true” warblers and have just some morphological similarities, related to adaptation and life to comparable environmental conditions. New World wood-warblers are small passerines that are also mostly insectivorous. During migration and at breeding sites, they vigorously examine trees and shrubs, skillfully extracting insects and arachnids from foliage and inflorescences, from the bark of trees and shrubs, and from other hidden places.
The Latin name of the New World wood warblers’ family – Parulidae – is associated with tits. The Old World tits belong to the genus Parus, described by Carl Linnaeus in 1758. Linnaeus, however, described one of the North American wood warblers – as the “American tit” – Parus americanus. The bird’s Latin name was soon slightly changed, retaining the root. This bird recently still was called Parula americana or Northern Parula and just recently was moved by taxonomists in another genus. Its Latin name now is Setophaga americana. However, the common name “Parula” is originated from the title given to this species by Carl Linnaeus. The entire wood-warbler family name – Parulidae – comes also from a Latin name designating tits – Parus and may be interpreted as “tit-like”. Obviously, both the species and the entire family have nothing to do with either tits or Old World warblers. However, our perception of passerine birds connects these unrelated taxonomic groups. Taxonomists consolidated the name of the family in 1947, highlighting the genus Parula as a type. It is noteworthy that the parula really looks somewhat like a tit: it has a slightly bluish color and when examining trees, especially birches, it can hang upside down, deftly clinging to thin twigs with its long fingers.
The New World Warblers – representatives of this family – occur entirely in the Americas. The family unites small insectivorous birds, many of which are brightly colored, especially males. All American warblers are rather small birds. The smallest species is Lucy’s Warbler (Oreothlypis luciae), weighing about 6.5 g with a length of a little more than 10 cm. Relatively large songbirds are Ovenbird (Seiurus aurocapilla) and Northern Waterthrush (Parkensia noveboracensis) with weight up to 25-28 g and length up to 15-16 cm. Most part of the birds from Parulidae family is associated with forest and shrub communities, nesting in shrub branches and in tree crowns. But there are also species that prefer to settle the nests on the ground, camouflaging them among the roots of trees.
Currently, 119 species of songbirds, belonging to 18 genera, have been listed to the family. It is believed that American warblers were originated and evolved in the northern part of Central America, where even now their species diversity is very great. During the interglacial periods, they spread far to the north, forming a group of long-distant seasonal migrants that fly to nest far beyond the tropical zones in the forested-tundra and taiga of North America.
These birds are found on migration in the Ottawa River Valley on their way to nesting sites in the northern boreal forests. The first migrants arrive in the Ottawa area in late April – early May. It is remarkable that some of the northernmost migrants appear in the northern latitude in late spring-early summer, they can be observed in the parks of Toronto or Ottawa only in late May-early June; they also begin to fly back prompt as early or mid-August. Thus, these birds have adapted to breed in a relatively short nesting season – one and a half to two months. In this period, they need to form pairs, find nesting territories, lay clutches, hatch, and raise chicks. Therefore, the size of clutches in migratory American warblers is quite large, they incubate up to 6-7 eggs and then feed large broods. For comparison, the tropical warblers from the same family usually have clutches with 2-3 eggs.
From May to early June, about 30 species of American warblers migrate through Ontario. Many of them stay for breeding in the orchards, parks, fields, and wetlands around large and small towns. But most migrants fly to the central and northern parts of the province and beyond its territory for nesting in boreal forests. Some the migratory songbirds, such as the Myrtle or Yellow-rumped Warbler (Setophaga coronata), American Yellow Warbler (Setophaga petechia), or Common Yellowthroat (Geothlypis trichas), are abundant and highly visible, while others are not always easy to spot even by a skilled naturalist. They migrate invisibly and quickly, trying to get to nesting places in northern latitudes as soon as possible. Many of those songbirds are characterized by a narrow food specialization. In nesting places, they hunt certain types of insect pests and caterpillars. In years when outbreaks of insect pests are observed, the populations of species-“specialists” also increases, then gradually reducing in accordance with the available natural resources.
It is not easy to spot many songbirds in the breeding places. Even having the bright color of plumage, they dissolve among the leaves of trees in the changeable play of light and shadow. But the presence of many species can be recognized by listening to their characteristic song. Some bird count techniques are based on the knowledge of bird songs and calls. For example, the famous “point count” method includes the identification of all birds around by their songs and calls from one point. The monitoring of breeding birds in North America has been conducted for over 50 years. Any citizen who has an interest in birds and their conservation may contribute his or her “two cents” to one of the bird monitoring programs by joining one of the environmental programs of Birds Canada, for example to the program on the Breeding Bird Survey or Ontario Breeding Bird Atlas. You also can contribute your bird knowledge to the citizen science program on birds survey – ebird, which holds the global database, collecting bird observation data from all naturalists.