Saturday, October 13, 2007

Sparrow Madness

Sparrows are much in the news the past week, as the chocolate and ochre masses sneak their way south, lurking in thickets, wetlands, and grasslands. I witnessed probably the largest fallous of White-throated Sparrows I'd ever seen last Thursday along Lake Erie, and other observers elsewhere along the lake reported big numbers. This is peak time for numbers and diversity, and THE time to find rarer skulksters like Le Conte's and Nelson's Sharp-tailed Sparrows. The latter two are more common than we think, and as birders learn how and where to find them, more are turning up.

Today dawned bright, beautiful, and cold - the first frost I've seen this fall. I was down around Deer Creek Wildlife Area at the crack of morning's first light, meeting up with banders Bill Bosstic, Kelly Sieg, Bob Placier and others in an effort to capture and band sparrows. Like us, birds have to warm up and get active, and things started rather slowly. By the end of the morning, though, we'd captured and banded 34 individual birds of eight species, including one particularly interesting species that I'll share at the end. Shown above is one of the nets snaking through some excellent sparrow habitat.
One of few non-sparrows that we got - a gorgeous Nashville Warbler.
One of our most common species, and one of the most beautiful both in appearance and song. The aptly named Song Sparrow is much more migratory than often believed. This one sports his freshly installed bling-bling; hopefully someone will catch him sometime in the future.

A fine-looking Swamp Sparrow. This species is a close relative of the Song Sparrow and is in the same genus, Melospiza. Swamps have rich rufous wings and tail, and can be very numerous in fields, particularly wet habitats, in fall migration.



We caught a number of Field Sparrows, including this fine specimen. By careful examination of various wing feathers, among other characters, banders can age and often sex birds.

A few Lincoln's Sparrows landed in our nets today. That's a Lincoln's in the back, close ally the Song Sparrow in the foreground. Lincoln's is in the same genus and similar, but is slightly sleeker, grayer, and finer streaking on the breast that generally lacks the central blob-like spot of the Song Sparrow. Far more Lincoln's Sparrows pass through in fall than is generally known; these birds are quite secretive and easy to miss.

The White-crowned Sparrows have arrived in a big way in the past few days, and we caught several. This was the most interesting species that I learned about today. As you may know, the closely related White-throated Sparrows come in two color morphs, like Rough-legged Hawks. This difference in color morphology is thought to be unique among North American sparrows. The bright white White-throateds with bold head stripes are white morphs; brownish striped birds are tan-striped morphs. Well, it turns out that the same interesting color morph arrangement may occur in White-crowned Sparrows. Kelly was privy to some as yet to be published information that aparently suggests this to be the case.

Today, we caught a few "tan-striped" White-crowneds, like the bird on the left. The bird on the right is a classic "white-striped". Traditionally, people would call the white bird and adult; the tan one an immature. Well, maybe not. Both of these individuals were hatch-year birds, meaning they were born this summer. Age can be determined by the degree of skull ossification, molt patterns, and feather shape. What we have here isn't proof that the tan bird won't later molt into crown stripes of white, like the bird on the right, but if word on the street bears out, it may prove to be a tan color morph and will remain like it is. I am eager to learn more about this development in our knowledge of White-crowned Sparrows. The fact that both birds above are apparent immatures is fascinating.

Sparrowing should remain good for the next week or few, so go hit some good fields if you can.


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2 comments:

KatDoc said...

Jim:

Thanks so much for the LBJ photos! Sparrows were my "spark birds," the ones that moved me from a passive backyard bird feeder manager to actively going out and learning about birds.

I am most interested in the White-crowned Sparrow story. When I first saw "brown-crowned sparrows" in my back yard, I described them to a dozen birders and asked what I was seeing. The answers were all variations of, "Some sort of sparrow, but..."

By watching their behavior, I became convinced that they were a variation of WCSP. The books called them "immatures," so I did too, but I'll bet that theory of two color morphs pans out.

~Kathi

Julie said...

In regards to "tan-striped" White-crowned Sparrows remaining tan-striped in spring, I disagree with that possibility.(if that is what the Blog is implying)

In my 18 years of banding birds and seeing several hundred White-crowns, it is my experience that the White-crowned Sparrows immatures in the fall have "tan stripes" vs. the white/black striped adults. If you see the White-crowned Sparrows in early March I have seen a couple White-crowned Sparrows with head feathers with a few brown feathers alongside the black feathers. Never have I seen a tan-striped White-crowned Sparrow in Spring.

It also documented in the any of the field guides I have looked at that the immature White-crowned Sparrows with tan stripes.

The research possibility needs further investigation before it goes to print.
Thanks for the opportunity to speak,
Julie Shieldcastle