Thursday, May 31, 2012

Sparrows: underrated

One of the highlights of exploring Presque Isle County, Michigan, where I do my now annual NettieBay field expeditions, is the sparrow diversity. Sparrows all too often get short shrift, and are sometimes bemoaned as "LBJ's" (little brown jobs) that are tough to identify. They're really not great identification challenges, though, and under careful inspection all of them are quite showy in an understated way. Sparrows also don't generally get their due when it comes to the big picture ecological services that they provide.

We had a total of 12 species of sparrows in Presque Isle County this time around, and I managed photos of a few species.

ASIDE: I once read where some time management expert said a person should only spend an hour a day dealing with personal email. I wish. After ten days away, and almost no dealing with such correspondence, I returned to a boatload of messages. If you read this, and sent me something, and I haven't responded, sorry. I'll do my best to to reply, eventually.

A Clay-colored Sparrow tees up on a small jack pine and imitates Pavarotti. The sound that emerges is somewhat less impressive, though. This close ally of the Chipping Sparrow emits an odd insectlike buzz, or if feeling especially robust, a short series of such buzzes. One could be forgiven for not even recognizing the Clay-colored's song as that of a bird.

Another denizen of the elfin jack pine forests is the Vesper Sparrow. This one has its feathers in a bit of a ruffle, courtesy of a windy day. Vespers are far more vocally complex than Clay-colored Sparrows, and deliver a beautiful melodic song that typically begins with a few downslurred whistles. Their outer tail feathers are trimmed in white, like a junco or meadowlark.

A Grasshopper Sparrow shouts his song from a ground perch. Much of this secretive sparrow's life is spent within five feet of the earth, and most of the time they're on the dirt. Non-singers are devilishly hard to locate, as they stick to dense growth and run about like mice. The song is actually a rather pretty affair, albeit reminiscent of an insect. A typical tune is a weak somewhat irregular trill, but they have a so-called "dawn song" that is more complex. But Grasshopper Sparrows hear much more than we do, and if you take the recording of one's song and slow it way down you'll get a sense of all the hidden notes that are masked to us, but audible to the birds.

Resplendent in his coat of chestnut is this Swamp Sparrow, singing his rich musical trill from a young tamarack. All of the open or semi-open wetlands in Presque Isle County have Swamp Sparrows. They are part of a group of songsters that might be referred to as "trillsters". Dark-eyed Juncos, Chipping Sparrows, Pine Warblers, Worm-eating Warblers, and perhaps a few others sound similar to many people, especially those just learning songs. Although all of them can be easily distinguished with practice - at least their typical songs - habitat can also provide clues to the singer's identity. None of the other trillsters other than Swamp Sparrow is likely to be heard singing in a marsh.

A Savannah Sparrow sings his pleasing t-t-t--zeeeee- zzzaaayyy from a meadow fence post. Even Hollywood must find the Savannah's song pleasant, as I hear it with some regularity in TV/movie/commercial sound tracks.

The Savannah Sparrow is named for the city in Georgia where the type (first) specimen was taken. But the species has an enormous distribution, occurring over nearly the entire North American continent. Something like 17 subspecies are currently recognized, and proposals have been made to split a few of the "groups" into separate species. While Savannah Sparrows are not long distance migrants, migrate they do and in big numbers. I was once with some banders that caught something like 80 of them in a small Ohio wetland in October, in one morning.

This is a cold, calcareous gravelly shoreline of Lake Huron, at Thompson's Harbor State Park in Michigan's Presque Isle County. It is not uncommon to encounter migrant Savannah Sparrows in the vegetation along the shoreline of this Great Lake, or any of the others. Migrant Savannahs have a tendency to favor such shoreline habitats, feeding and foraging in the low vegetation that buffers the shore.

Note the dominant grassy-looking vegetation that extends nearly from the water's edge to the gravelly dune at the right edge of the photo. It's an interesting plant species, and factors into the important role that Savannah Sparrows play ecologically. That swath of lakefront land between the water and the dune is a brutal place to grow. Ferocious storms crop up along the Great Lakes with regularity, and storm-driven waves batter the lakeshore. Most plants cannot deal with such an environment.

The dominant grassy-looking vegetation in the previous photo, growing in the lakefront no man's land, is this interesting species, Baltic rush, Juncus balticus. It is one of few plants that can survive and thrive in such a hostile place. Note how the rush grows in a perfectly straight line.

This is why Baltic rush grows in such linear fashion. I took the liberty of digging one out, and washing it off so we could better understand its growth habit. Baltic rush is highly rhizomatous; its shoots emerge from a well entrenched subterranean rhizome that sends up stems at regular intervals. That rhizome is tough as steel cable, and serves to anchor the rush and hold the plant in place even during the most savage storm-driven poundings.

One effect of Baltic rush's prolific dominance as that it serves to create sheltered micro-habitats in which other plants that are less hardy can find a foothold. This is one of the species that prospers in shoreline Baltic rush shelters, the Garber's sedge, Carex garberi. It is a tiny sedge, often standing no more than a few inches in height, which places its fruit at just the right height to be plucked by foraging sparrows.

Garber's sedge is a one of a few species in the massive Carex genus of sedges that has odd little fruit that resemble tiny berries. They're more succulent and for want of a better word "tasty" looking than the dry papery fruit of most sedges. I once had a discussion with the great University of Michigan botanist Tony Reznicek about sedges in the section Bicolores, which includes Garber's Sedge. Tony felt that the peculiar fruit of these species was an evolutionary adaption for dispersal by sparrows, and I totally agree with him.

Foraging Savannah Sparrows in migration undoubtedly consume the fruit of Garber's sedge and other plants that occur along shorelines. The actual seed of a sedge is termed an achene, and they are hard and bony, and concealed within that fleshy-looking fruit. Perfect for surviving the ride through a sparrow's digestive tract, and many of the achenes no doubt eventually emerge intact from the sparrow's posterior end and often probably far distances from where the bird ate the fruit.

Over the LONG haul, which is how we really ought to look at nature and the environment, sparrows such as the Savannah play a major role in the dispersal of plants. Certain plants, such as the Garber's sedge, are probably intimately linked to certain birds such as the Savannah Sparrow and depend upon these feathered couriers to transport their seeds to new sites, thus starting new plant colonies.

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3 comments:

zippiknits said...

Sparrows, because they are so full of life(and sometimes very raucous)always make me smile. Thank you for the tour of their lake-land habitat, and the gorgeous pictures. I know how hard it is to get them!

Baltic rush reminds me of what we call "Devil Grass" in the West. Chippies like to eat the tiny seeds of that one.

Kim Smith said...

Jim, thanks so much for the helpful hints about identifying sparrows! I've been working on improving my sparrow ID skills lately, so will bookmark this post for reference.

Jim McCormac said...

Thanks for your comments! Glad the post helped you to identify these little brown birds, Kim!