Andreas Jonsson's Weblog

About a douzen species of wood warblers in different fall plumages

Last evening I was invited by Jean Iron to attend the monthly meeting a the Toronto Ornithological Club. The main attraction was a workshop on fall plumage wood warblers. While in the spring and summer this is a colourful group of birds, in the fall, they wear much plainer colours, and are difficult to separate by species. To add to the challenge, male, female and first year (immature) birds have different plumages. At this workshop, lead by Mark Peck of the Royal Ontario Museum, museum specimens of most regularly occurring wood warblers in Ontario were present in fall plumages for adult males, adult females and first year birds. During the workshop we had the opportunity to study the subtle differences between the different species, sexes and ages. Quite a dull task to the non-initiated, but a very useful exercise to the dedicated birder. In this post I’ll show pictures of some of the specimens and briefly discuss the fall plumages of Connecticut and Mourning warblers.

From the front: three Connecticut warblers, three Mourning warblers, three Nashville warblers, and a single Wilson's warbler.

Lined up above are two species of the Oporonis family: first, three specimens of the elusive Connecticut warbler, and second, three specimens of its near relative the Mourning warbler. For comparison three specimens of Nashville warblers and a single Wilson’s warbler are also shown. A closeup of the Connecticut warblers is shown below.

Connecticut warblers (front) and related species (back). Note the cotton stuffing in the birds eyes.

At a distance these birds can appear confusingly similar, but looking up close, starting with the Connecticut warblers (see photo below), note that the male (top) has a darker throat and breast with a sharper border to the yellow belly than the female (middle). The first fall bird (bottom) is overall less yellow with a dirty brown throat and breast area that merges more smoothly to the colour of the belly.

Connecticut warblers (from the top: male, female, and first fall immature)

Note the writing on the labels, they tell a story for each of the birds. These three birds were captured on Toronto Island and on Long Point between 1929 and 1935.

Labels for the Connecticut warblers (from the top: male, female, and first fall immature)

The Mourning warbler (below) is very similar to the Connecticut warbler, but a little smaller, has shorter undertail coverts, and the male often wears black colours on the throat and breast also in the fall. (Note that these images do not show the eye ring of the birds.) The differences between the sexes and ages are similar to those for the Connecticut warbler, mentioned above.

Mourning warblers (from the top: first fall immature, female, and male)

The adult male was collected by James Baillie in Rainy River in 1929. The female and the first year immature bird were both collected in Toronto, in 1957 and 1934, respectively.

Labels for the Mourning warblers (from the top: first fall immature, female, and male)

The following seven birds are Ovenbirds (with white base colour) and Northern waterthrushes (with a slightly yellow wash).

Ovenbirds and Northern waterthrushes

Finally, have look at this 104-year old (below). It’s an adult female of the highly endangered Kirtland’s warbler (nearly extinct just 50 years ago), collected in Michigan in June 1906!

Adult female Kirtland's warbler