The unmistakable Yellow warbler

By Jeanette Rive

The warblers are a group of songbirds greatly anticipated every spring by enthusiastic birders who excitedly flock to their known habitat as soon as the first sightings are reported. These mostly unrelated birds share the following characteristics: they are all small, vocal and insectivores, eating mostly caterpillars, spiders and any flying insects. Their name originates from an old French verb, “verbler,” which means singing in trills.

In our area of Eastern Ontario, there are some 38 different species of warblers, called wood warblers because they are mostly arboreal. Warblers, especially males in full breeding plumage, are colourful, and their names often reflect the distinguishing markings of the species – Yellow warbler, Black-throated Blue warbler, Black and White warbler, Yellow-rumped warbler, Chestnut-sided warbler, among others. They are small, ranging from the tiny 7 cm Northern Parula to the slightly larger Ovenbird at 11 cm. They weigh about 10 grams – about the weight of four jellybeans! They are extremely active little birds, flying from shrub to shrub, hiding behind leaves, frustrating photographers and challenging birders to identify them correctly when they are only seen for a few seconds.

Yet they are migratory champions, spending the winter in Central and South America, then flying north to breed in our arboreal forests. The most extreme traveller is the Blackpoll warbler, which flies from Alaska all the way to Brazil over a period of three days. In preparation for these arduous journeys, warblers gorge on high-fat berries and double in weight. The flight south is non-stop but when returning north in the spring, the birds stop along the way to catch insects. However, with climate change affecting the seasons, birds are at risk if their timing does not coincide with the seasonal cycles of the insects.

Warblers are not seed eaters, so you won’t see them at your feeders, but I have heard of the occasional report of warblers in a Glebe garden. Looking further afield, they are often seen at the Fletcher Wildlife Gardens and the Arboretum, among the shrubs and trees along the Rideau Canal and Rideau River and occasionally at Brown’s Inlet and Patterson’s Creek. The best location is the Britannia Conservation Area. Patience and a quick eye are needed!

The Yellow warbler, sometimes called the “summer yellowbird,” is among the most widespread and most visible of all warblers. The male is bright yellow with orange streaks on its breast, while the female is a pale lemon yellow. They usually spend time in small flocks but when the breeding season starts, the male becomes territorial, staking out a suitable nesting area, chasing away any intruders. He will then start incessantly singing a whistled tune “sweet, sweet, sweet, I’m so sweet” to attract a female – he may sing up to 3,000 times a day!

Parental responsibilities are shared, though each has set duties: the female builds and maintains the sturdy cup-shaped nest in a tree, incubates the eggs and broods the chicks; the male guards the nest and brings insects to the female to feed the chicks. A clutch is usually three to six eggs which hatch after about 11 days. The chicks are brooded for eight or nine days – they then leave the nest though their parents feed them for about two weeks. After that, the family breaks up with some chicks following the mother, some staying with the father.

Warbler nests are frequent victims of brood parasitism with Brownheaded cowbirds laying eggs in their nests in hopes the chicks will be reared by the warblers. Not only have warblers developed a distinct alarm call to alert other birds to the presence of a cowbird, they have also evolved a unique way to combat them. When the female sees the egg of another bird in the nest, she will cover all the eggs, including her own and build a new nest directly on top to smother the eggs. She will then lay a new clutch of eggs. Nests up to six layers deep have been found!

The southward migration can start as early as July once breeding and fledging are completed, but usually August is when mass migration starts again.

Summer can be very hot for small birds. They can cool down by panting and opening their bill wide to cool their throats and air sacs, but they need water to replenish the water lost through panting. If possible, set out a little bird bath in your garden, out of reach of an opportunistic cat, to keep birds hydrated.

Happy birding this summer and keep your eyes out for unusual tiny birds.

Jeanette Rive is a Glebe bird enthusiast and Glebe Report proofreader.