Saturday, March 28, 2009

Owls and falcons and convergent evolution

If you compare owls with other owls and falcons with other falcons, you will find significant variations. Some owls are strictly nocturnal, while others are diurnal or crepusular in their habits. Some are buoyant and have light wing loading and others are powerful and have heavy wing loading. Some depend almost exclusively on hearing to hunt, while others make effective use of their eyes in low light. Some falcons hover, while others stoop at high speeds. Some falcons eat birds almost exclusively, while others will eat mammals and some eat insects. Some falcons are long distance migrants, and others are sedentary.
What gets interesting to me relates to the convergent evolution of owls and falcons as compared with hawks. Both owls and falcons tend to be cavity nesters. Some will use stick nests, but will never build or repair them; whereas most hawks will build and repair stick nests and rarely, if ever (to my knowledge) use cavities as nests. Both owls and falcons tend to cache food for future use, but rarely eat carrion, in contrast to hawks.
Both owls and falcons defecate by muting straight down in dribbles, whereas hawks slice and can project their waste several lateral feet. It is not unusual to find a mound of poo under favorite owl perches and spaghetti-like strands of whitewash (excrament) on the rocks below favorite falcon perches; whereas hawk excrement is projected over a wide area under roosts or nest sites.
Why would owls and falcons have not one, but several, common characteristics of this sort? Since life is a product of genes, which compress time, space and experience into the tissues of living creatures, are there specific genetic similarities between owls and falcons that could be traced and identified?
My observation is that a lot of genetic work is being done now on raptors, but much of it is management driven; that is, the genes of populations are compared as mechanisms for protections or management of isolated, fragmented, or endangered populations. That is where much of the funding in biology is these days, unfortunately.
I would love to see the results of new work by some emerging biologist/geneticist who has the wherewithal to initiate evolutionary studies of raptors that explore the genetic mechanisms of common behaviors and convergent evolution. Why do owls usurp and then abandon nests instead of constructing and maintaining them? Was it always that way in evolutionary terms?
What effect might global climate change have on the behaviors of these birds? Will birds that can cache food have a survival advantage over those that do not? Will carrion eating emerge as a new survival strategy?
These are interesting things to ponder and I hope that some inquisitive emerging scientist decides to make a career investigating these sort of questions.
Stan Moore

No comments:

Post a Comment