Who’s ready for a brief wood-warbler quiz?

It’s the Q and A portion of the day, so feel free to satisfy your wonderment with the following questions (answers appear far below):

1. To which family do some taxonomists believe is most closely related to wood-warblers?

2. If you include North, Central, and South America, and the West Indies, how many wood-warblers exist?

3. Although most wood-warblers possess small bills, which two species have more robust ones?

4. Which common wood-warbler has rictal bristles (like flycatchers) to help it sense prey while pursuing insects?

5. Although most songbirds have ten functional primary flight feathers on each wing, how many do wood-warblers possess?

6. Among the 53 typical annual breeding North American wood-warblers, what’s typical about their breeding behavior in contrast to Central and South American wood-warbler species?

ANSWERS:

1. Some taxonomists place wood-warblers closest in relation to the tanager family, Thraupidae (sometimes treated as a subfamily, Thraupinae, of Emberizidae). Other researchers believe they are nearest to the New World finches family, Emberizidae.

2. 126 species amidst 28 genera.

3. Yellow-breasted Chat and Yellow-Rumped Warbler.

4. American Redstart.

5. Nine.

6. North American wood warblers remain monogamous for the breeding season, while Central and South American pairs may persist together for longer periods.

Wilson’s Warbler: Abundant, Yet Vulnerable

You might think the Wilson’s Warbler is one of the most abundant warbler species while traveling through Alaska, most of Canada, and south through the western USA to southern California and New Mexico. Your supposition would largely be correct.

But long-term trend analysis indicate recent population declines, especially in the western portion of the species’ range. The most likely problem is large-scale destruction of riparian habitat.

Nesting on or near the ground at elevations that vary from sea level to the alpine zone, the three subspecies of Wilson’s Warbler encompass a wide geographical area that spans from eastern Canada to Alaska and portions south into Utah, New Mexico and central California.

Interestingly, the subspecies may occur together in non-breeding range, with all three subspecies possible in Panama.

Although it shares its genus name – Wilsonia -- with other wood-warbler species – (Canada and Hooded), Wilson’s is by far the most common. All three species possess rectal bristles (small , highly-sensitive feathers at the base of the bill) that are utilized during “flycatching,” a foraging behavior that can sometimes help with field identification.

Mr. Warbler, what’s the difference between “New World” and “Old World” warblers?

Thanks for the question, Barbara S. in Spokane.

Noting the New World is a geographic designation corresponding to the Western Hemisphere, Old World warbler species live within the Eastern Hemisphere areas of Europe, Asia, and Australia – with only a few species (e.g., gnatcatchers) existing in the New World/Americas.

Approximately 350 Old World warblers occur in the Sylviide family. New World warbler species total around 120 species and most of them are in the Parulidae family.
(Approximately 52 are annually seen in the USA north of Mexico, with the most common being Yellow, Common Yellow-throat (above photo), Yellow-Rumped, among others.)

In fact, the Olive Warbler (the sole Peucudramidae family member) is the only non-Parulidae family species among North American wood-warblers to occur north of Mexico.

Note there’s also the Australasian warblers in the Acanthizidae family that include gerygones, thornbills, and scrubwrens,.

This family is native to Australia, Indonesia, New Zealand, and the south-west Pacific. Australia hosts 35 endemic Acanthizidae family members and New Guinea 15. A single species is found in Vanuatu, New Caledonia and the Solomon Islands, and three species occur in the New Zealand region, including endemic species in the Chatham Islands and Norfolk Island. In Asia two species are restricted to Indonesia and another is found in the Philippines and on mainland Asia. Most species are not migratory, with the exception of the gerygones.

Which wood-warbler travels the longest migration route?

Thanks for the question, David in Studwell, MN.

The answer: Blackpoll

Autumn studies of the routes south-traveling Blackpoll take have been extensive. Through banding at stations where the same individual has been studied, researchers have determined some Blackpolls travel more than 5,000 miles one way from Alaska to Brazil.

For many Blackpoll migrating populations, migration occurs over the Atlantic Ocean from the northeastern United States to Puerto Rico, the Lesser Antilles, or northern South America.

This route averages 1,500-2,000 miles over water, necessitating a potentially non-stop flight of up to 88 hours. To complete this migration feat, many Blackpolls nearly double their body mass and prefer to take advantage of a shift in prevailing wind direction to direct them to their destination.

What’s an example of a “superspecies” in the wood-warbler family?

(The Black-Throated Gray Warbler in the above photo is one of five species within the Black-Throated Green superspecies group.)

Thanks for the query, Ms. Jones (in Santa Barbara, CA).

Think of a superspecies as a group of related species that evolved from a common ancestor, but live in distinct ranges apart from each other. A good example of a superspecies is the Black-Throated Green Warbler group that includes this species as well as Townsend’s, Hermit, Golden-Cheeked, and Black-Throated Gray Warblers.

Each of the latter four species in the above group is thought to have evolved from its Black-Throated Green ancestor. As this species expanded from its southeastern USA deciduous forest territory into coniferous forest created by the most recent glacial advances, isolation occurred among populations. As generations of separated populations slowly spread west and north throughout lower North America, each population became a divergent “island.” Gene flow ceased as reproductive isolation caused speciation to occur over eons. The resulting five species share various field marks, but also express their own unique characteristics.

Nonetheless, despite their status as species, hybridization sometimes occurs among species within a superspecies, including the Black-Throated Green superspecies wherein populations of Townsend’s and Hermit hybridize in Oregon and Washington. To simplify, where both species occur, over time Townsend’s appear to usually dominate and increase in number.

More technical, the five species within the Black-Throated Green superspecies have parapatric distributions. That is to say, each of the five species has ranges that do not significantly overlap but are immediately adjacent to each other (and/or occur together in a narrow contact zone, with the aforementioned reference to Townsend’s and Hermit Warbler hybridization a scenario where overlapping occurs).

To learn more about this subject, read a classic article by R.M. Mengel titled “The probable history of species formation in some northern wood warblers.” One source where this article appears is in a 1964 edition of “Living Bird” (page 943).

Is the American Redstart a vagrant in the western USA?

Answer:

Thanks for the question Lori Anne (in Seattle).

Although many eminent, well-respected authors suggest, for example, a California sighting of American Redstart deserves a “vagrant” status designation*, I beg to differ.

(* = vagrant status applies to a bird species that is found far from its typical breeding or non-breeding area.)

That’s because my research suggests small populations of this species periodically to annually nest in small numbers in n.w. CA. In addition, other breeding range individuals occur as far west as s.w. Idaho, Oregon, and Washington.

As a result, I believe it’s more appropriate to refer to autumn and winter sightings of this species in northern California as “casual visitors.” That term qualifies a bird species’ status as one that is slightly removed geographically from where it is expected to be seen in either breeding or non-breeding range.

Ultimately, it’s possible a Bay Area (e.g., Point Reyes National Seashore) sighting of this species could be an individual that spent the breeding season in farther north latitudes, such as the aforementioned n.w. CA area (or Alaska, more probably, where populations in greater abundance breed).

In any event, the entire species of American Redstart are thought to be locally abundant in much of their breeding range, especially if suitable habitat remains. However, it should be noted that populations have declined where forests have been fragmented by development and where urbanization has replaced habitat.

Is it possible to distinguish the call notes of Audubon’s vs. Myrtle Yellow-rumped Warbler during the non-breeding season where they occur together?

Answer:

Obviously, these birds are NOT singing during the non-breeding season, but you do often hear loud chip or call notes where Audubon’s and Myrtle Yellow-Rumped Warbler patrol during the non-breeding season.

In many cases you can hear how the Myrtle (one of the subspecies of the Yellow-rumped Warbler species) has a flatter and softer chip note than the Auduon’s.

The “ch” component of the call note is weaker for the Myrtle and it often gives many calls in rapid succession.

However, be careful. Intergrades (individuals that display visual characteristics specific to both Audubon’s and Myrtle) may announce call notes of the other subspecies. In other words, it’s possible to see a bird that looks like an Audubon’s, but it’s call note sounds like a Myrtle. This individual could likely be an intergrade.