Tuesday, Oct 21, 2008
Category: Birding at the Chico

A dense morning fog was good for photography, but not so good for birding.  But as the fog lifted, the birding improved.  Migrants were common in the Kochea weeds and included both large flocks of Mountain and Eastern Bluebirds. Another migrant, seemingly interested in the same weedy fields, were American Pipits, whose flight calls gave away their location.

The birding surprise, however, was the 1st Ranch record of Sedge Wren at the RMBO Banding Station.  Although Sedge Wren breeds due north of Colorado, it is a rare migrant in the state, probably because it passes through undetected.  This was another species that was found in dense noxious weeds, this time in Canada thistle with an overstory of Russian olive.  This was a real treat and the bird, though a skulker, gave repeated good binocular views from very close range.


Posted by Bill M. on 10/21/2008

Migration - Long-billed Dowitcher
Category: Birding at the Chico

Conditions at Chico Headquarters Pond are currently excellent for observing migrant sparrows and shorebirds.  Water levels are low enough to expose mudflats around the enitre shoreline.  The inflow area on the east bank is a great spot to look at the edge of the northern marsh for both secretive marsh birds like Sora and Virginia Rail, who barely venture out of the vegetation to feed, and for viewing southbound shorebirds, now at the tailend of their long migration.

Yesterday, I watched an uncommon Pectoral Sandpiper feeding with a flock of the much larger Long-billed Dowitchers.  Long-billed Dowitcher is a common migrant in Colorado in Spring, but if you are new to birding you might not recognize it in the fall. 

In the photo here you can see three ages of Long-billed Dowitcher.  A brightly colored bird in breeding plumage from May is at the top.  The middle bird is a juvenile, as told by the rufous-edged feathers on the feather grouping called scapulars, contrasting with the dull gray nonbreeding or basic feathers.  The rufous-edged juvenal feathers will be replaced in the next month, so that the remaining plumage will be all gray, as in the bird at the bottom.  The birds will keep the basic plumage until increased daylight stimulates a small region of the birds'  brain to produce testosterone in male birds, and estrogen and another hormones in females, that will trigger another molt until the birds again look like the bird in the top photograph.

Long-billed Dowitcher breeds along the Arctic coast of Alaska and western Canada and winters along both of our coasts, the Gulf of Mexico, and along coastal Mexico and the northern Central America coasts.  Like all shorebirds in the large group of birds related to Long-billed Dowitchers, the scolopacids, they always lay four eggs, and never more.  Egg production requires a great deal of calcium and this species and other Arcitc nesting shorebirds ingest lemming teeth and small bones found lying on the tundra to overcome potential calcium deficiencies.

At Chico, there is occasionally a rarer species of dowitcher, Short-billed Dowitcher, that in all but its juvenal plumage, looks very similar to Long-billed.  Differences between the two dowitcher species will be the subject of a speparate post.

Posted by Bill M. on 10/19/2008

Fall Woodpeckers
Category: Birding at the Chico
A number of species of woodpecker have been seen this fall near the RMBO Banding Station, including lots of Northern Flickers, single Red-bellied and Red-headed Woodpeckers, a male and a female Red-naped Sapsucker, a Downy Woodpecker or two, and the resident Ladder-backeds.

Does that mean there are a lot of dying trees around?  It could, but the flickers were mostly interested in the fruits of Russian olives and both Red-headed and Red-bellied will capture flying insects.  The sapsuckers, as the name implies, suck a lot of sap by drilling rows of small holes in trees, getting tree sap to ooze in a manner similar to humans tapping maple trees for their sugary treats.

Male and female Ladder-backed Woodpeckers (the male with the red cap) were setting up a winter territory, both using a powerpole for a sounding board.  Later they foraged on the ground and hammered on cholla cactus extracting beetle larvae, and on occasion they ate the yellowish fruits off a cholla.

Posted by Bill M. on 10/13/2008

Migration - Sandhill Cranes
Category: Birding at the Chico
Nothing is quite as thrilling as hearing the calls of recently formed flocks of Sandhill Cranes flying.   Today, out in the Sand, there was a small flock of five cranes resting in the new winter wheat field.  During migration, cranes wait until a few hours after sunrise to continue their flights, waiting for thermals to form.  The thermals or updrafts help keep the cranes aloft, reducing the amount of energy spent during the very long migration.

Each of the 15 species of crane has different calls, and the calls are determined partially by the length and the positioning of each species' trachea.  During spring at pair formation, recently formed crane pairs use unison calls that differ from the synchronous calls of well-established pairs.  The female's voice is usually higher-pitched than the males. Because their tracheas are coiled inside their sternum, cranes able to make a variety of wonderous sounds.  

Cranes, along with storks, flamingos, geese, and swans, but unlike herons, fly with their necks stretched straight forward.   Becasue of their great size, crane landings are viewed as giant gray birds with wings extended, heads semi-erect, and legs dangling.  During the last few seconds of the landing, the tail and wings are spread out and down, with wings flapped a few times before assuming their normal stance.  

Aldous Huxley described a flock of Sandhill Cranes as sounding first "like a tinkling of little bells", then, as they fly closer as the "baying of some sweet-throated hound", and finally as "a pandemonium of trumpets, rattles, croaks, and cries."

I heard, and then saw, five flocks of cranes fly over today.  On the Chico crane migration should continue through the month.

Posted by Bill M. on 10/10/2008

Migration - Mountain Bluebirds
Category: Birding at the Chico
Last night the temperature dropped to near freezing.  The result was a lot of birds were seen this morning heading south, especially Mountain Bluebirds.  As mentioned here before, there are three species of bluebird, and all three have been recorded on the Chico.

Continuing the molting birds theme, not all Mountain Bluebirds are bright blue.  During the winter non-breeding season, there is no benefit for adult males to wear their brightest feathers, as doing so would draw the attention of wintering raptors.  However, the males are always brighter than the drab females.  Female Mountain Bluebirds, to the uninitiated, might look superficially like the females of Eastern, and especially Western Bluebirds.  However, Mountain Bluebird always has a thinner bill and always (when seen well) shows  thin, light-colored feathering across the base of the bill.  In Mountain Bluebird, the bill itself is dark, unlike the yellow-based bills of the other two bluebird females.

Looking at the photo in the grouping, there is a breeding male (lower left), a first winter male (lower right), and on top, two first winter females.  The two females appear to have different  coloration and  that is because the entire population of Mountain Bluebirds has both gray and rufous females in it.  Gray females are easily separated from females of the other two bluebird species, but rufous females can look similar to females of Eastern and Western Bluebirds, thus looking closely at the bill coloration will clinch any identification uncertainty.

Both Mountain Bluebird and Eastern Bluebird winter on the Chico during some winters where they add a bit of color to the landscape. 
Posted by Bill M. on 10/07/2008

Chestnut-collared Longspur
Category: Birding at the Chico
Chestnut-collared Longspur is listed as a rare migrant and wintering bird on the Chico, but actually they are probably regular late September and early October migrants that are just overlooked.  They can be found out in the Sand with flocks of Horned Larks, especially when the flocks come to water areas to drink.

One of the interesting features of longspur plumage is how it changes over time.  The photo at the top is a breeding male Chestnut-collared Longspur.  The photograph in the middle is a 1st year male.  It is easy to see a partially black breast in the middle photograph.  As the buffy-tipped feathers wear during the late fall through early spring, the resulting plumage will look like the bird on top.  So, the breeding plumages of all longspurs results from feather wear and not from molting new brightly-colored feathers like most birds do.  Even the drab 1st-winter female at the bottom will change plumage, but because she is a ground-nester, her plumage, while brighter than the bird at the bottom, will have many shades of earthy tones that enable her to be hidden while sitting on her nest.  

Unlike the flight calls of the other three species of earth's longspurs, Chestnut-collared's flight calls are very distinctive, and to me they sound like sweet kiddle kiddle kiddle, easily heard as are coming in to land and also when they burst into their nervous erratic flight.
Posted by Bill M. on 10/05/2008

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