Tuesday, April 6

Tree creatures

I got my river walk in this morning close to noon. Wind-whipped waters. A few Canadian geese still hanging around. Great huge sun-bleached cottonwood trees like beached creatures lying prone beside the river. Looking like great huge grey-almost white bones. I don't think the trees ever have been in the river but they could have been. They are old and are certainly in the flood plain.

Saturday, April 3

Hiking on the mesa & why mockingbirds mock

I hiked for about 35 minutes on top of West Mesa --- such a nice place. Some wind but not bad. Yellow grass bending in the wind. Bird songs carried by the wind.

There, I can see for 75 or so miles to the north to the Sangre de Cristo mountains near Sante Fe,
to the east I see the nearby Sandia Mountains, and to the west, the extinct volcanoes. But mostly, I bask in a vast open area of sky, clouds and grassland. I heard meadowlarks and mockingbirds singing.

Later, at home, I wondered why mocking birds imitate calls of other birds. What possible benefit could they get from such behavior? Birds usually sing to attract a mate or defend territory. How could singing another species' song help?

So, I looked up mockingbirds and learned the males are indeed trying to attract female mockingbirds by increasing the size of their repertoire.

Apparently, the mockingbird doesn't fool other birds all of the time. Maybe a mockingbird can effectively copy a repetitive song like the Carolina wren's or a red-winged blackbird but not long complicated songs like the song sparrow's. The mockingbird female, however, knows a male mockingbird when she hears one, no matter what song he imitates.

A male might have 50 to 200 songs in his repertoire and continues learning new ones all his life. Females sing, too, but not as much as males. Mockingbirds sing the loudest in early morning twilight, but also sing at night, especially if the moon is full, they are male and single.

Actually, we don't fully understand why a mockingbird mimics other birds' songs. The increased-repertoire theory seems reasonable and is probably true. Bird experts have hypothesized other reasons too:
  • defending an individual mockingbird's territory against others within his species
  • promoting recognition of an individual mockingbird
  • deceiving competitors by making it appear that many of the competitor's predators live in the area.
The birds also mimic other animals and mechanical sounds (such as car alarms).