Thursday, January 27, 2011

photo by Len Warren
                           Need Crissal Thrasher?.......Shoshone, CA 92384

Crissal Thrasher- (Toxostoma crissale)- A common resident of Shoshone,(10-20 pairs) very secretive, more easily heard than seen. Crissal Thashers thrive in the mixed riparian, vegetation along the Amargosa River, dominated by Honey Mesquite and Screwbean Mesquite. The Crissal Thrasher rarely flies, preferring to walk or run around its territory and will mostly run for cover when disturbed by a potential predator *wi. In late January, the male begins to sing. A member of the mimidae , a natural mimic, the male mimics the songs and calls of local and migratory birds. The nest is usually very well hidden, in deeper, darker, denser vegetation. Crissal Thrasher is very difficult to observe. Breeding season Jan-June  provides the most reliable looks at this species. Listen and look for the male singing from various high perches throughout their territories. Approach slowly, do not follow too closely, listen carefully, and you will be rewarded by a close look at a pair of Crissal Thrashers on their breeding territory. Please  respect their hard earned space by minimizing playback, and learning their behavior, songs and calls.

Tuesday, January 11, 2011

Verdins are fascinating

photo by Colin Wooley
Verdins in Shoshone are fascinating.They are year round residents in mesquite dominated desert riparian areas.. They build wonderful fascinating dome shaped nests of thorny twigs, lined with a thick layer of feathers.The nest building is done by both the male and female.If you are lucky enough to find a Verdin nest under construction, the real work of art is revealed . A lacy dome or globe is formed by expertly propping, weaving, and maneuvering the thorny twigs into place.As the sphere forms,the adults collect spider webs by actually grabbing the web, and wrapping it around the beak by moving beak in little circles and figure eights.The webs are then taken to the nest and used  for bonding material. The presence of fresh spider webs and greenery  is a clue used to determine which nest is the active nest .During nest building , the often male arrives first, looks all around, gives a single note call, maybe the all clear. The female then arrives with a big twig, huge for a 3-4 inch bird, or a beak full of feathers. Although the nests are easy to find, Verdins are sometimes  very careful about showing their active nest location. They sound alarm calls when you enter their territory,  and sometimes won't go anywhere near the nest if you are close. They can  have very large territories for such little birds.They can build a nest and lay  an egg in as little as 4 days! A typical  Verdin territory in Shoshone can have as many as 10 inactive nests and one active nest within their territory..They often build a nest and do not use it. Some literature states that the male builds several nests and the female chooses one. I have not found this to be the case at all. Although they often abandon nest building attempts, they seem to build together  or abandon together .Occasionally a pair begin a nest, completely stop building, nest nearby, then finish the original nest and use it for a second brood.Verdins also have been known to build their next nest while  still incubating at the first nest. Another interesting nest building method is to stack a second nest right on top of a previous one, or right below it for that matter.Once,in Arizona,  I have seen a pair actually building 2 nests  simultaneously, intertwined so that the top of one made the bottom of the other, they made two entrance holes, but then only finished, lined, and laid eggs in one of the nests. In winter, they seem to loosely hold territories. They build  roost nests which are often smaller and sometimes not lined. Some winter roosts are well lined.The lining used for breeding season is the softest downiest cushion that you would ever imagine. When you carefully reach into a Verdin nest to check it's contents and are lucky enough to find a B-100,this means 100% finished and lined and ready for eggs, you'll be amazed at how plush the lining is. The lining material is a precious commodity in the desert.
  Verdins have several vocalizations. The song vs. the call can sometimes be difficult to determine.The male "song" can be a one, two, or three syllable whistling " tseet" or "tseet- tsoor" or "tseet- tsoor -tsoor", the female's response call is a quieter version of the single note "tseet". There are gentle, quiet, warbling,musical, twittering calls used by the pair when they greet one another near the nest.  Both sexes use the scolding call a repeated, staccato chip, chip, chip or tip, tip, tip, and the predator call..The predator call is difficult to describe but it is a repeated, je-je-je-je-je, a machine-like sound that reminds me of a cactus wren song, but higher pitched.During winter, I have heard only the scolding call, until yesterday, when I began to hear verdins using the tseet single note call all over Shoshone. Male Verdins will soon become aggressive toward each other, than pair formation will begin. Nesting usually Peaks in late April,  but continues in Shoshone till July.
in 2010 there were 20 pairs of Verdins on the Shoshone nesting research plot. PRBO (Point Reyes Bird Observatory) has conducted a long term research project here since 2005 that monitors all speciesof songbirds nesting along the Amargosa River.