Human Impacts

Loggerhead Shrikes (Lanius ludovicianus) are fairly common in the Agua Fria River Basin, but the one shown here is the first one I have photographed.  This fellow was quite curious about me, and while I stood talking to him, fluttered to within about ten feet, then perched nearby while I tried for a good camera angle.

Male and female shrikes share the same white,  gray, and black plumage, and both parents feed their young.  This big-headed little bird hunts insects and small lizards, mammals, and birds from fences, trees, and shrubs.  Shrikes have strong beaks but relatively weak talons.  When they make a catch they carry their prey to a thorny tree or shrub, impale it, and tear it asunder with their powerful beaks.  If prey is plentiful, some will be left impaled for later use.  These ‘left overs’ are perhaps used to mark territory and attract females.

Loggerhead Shrikes have declined throughout the United States, especially in the Midwest and Northeast.  Breeding bird surveyors (Corman and Wise-Gervais 2005) found the bird nesting throughout Arizona, but according to Sauer et al. (1995), there has been a measurable decline.  Roads, pesticides, and other threats are discussed by Julie Craves (2007).   Shrikes prefer open woodland and shrubland with abundant perches and thorny plants.  As these habitat types fade away due to the spread of invasive weeds and the increase in wildfires, shrikes will become scarce.  But until the chaparral is burnt out and the megapolitans arrive with their bulldozers, you can see these unusual little birds just about anywhere in the upper Agua Fria River Basin.

References (Look for additional references in the earlier post on Arizona Birds)

Corman, T.E., and C. Wise-Gervais. 2005. Arizona breeding bird atlas. University of New Mexico Press, Albuquerque, NM.  636 p.

Craves, J.  2007.  Species profile: Masked predator, Loggerhead Shrike.  Birdwatching.  August 22, 2007.  Online in the bird profiles section at:  http://www.birdwatchingdaily.com.  (On the BirdWatchingDaily website go to ‘getting started–bird profiles–August 2007 edition.)

Sauer, J.R., S. Orsillo, and B.G. Peterjohn.  1995.  Geographic patterns and population trends of breeding and wintering Loggerhead Shrikes in North America.  Proceedings of the Western Foundation of Vertebrate Zoology 6: 128-141.

Arizona Ants

Ants are a critical component of the earth’s terrestrial ecosystems.  They consume and break down large amounts of material, they control the populations of numerous species, and they provide food for many others.  For instance, ants make up 40% of the diet of the Northern Flicker, a common Arizona bird.  Despite being small and not so visible, ants account for 15% to 25% of all animal biomass on our planet’s land surface—far more than any other animal group.

So how much do the ants weigh?  Using guesstimates from the references I made assumptions that the average ant weighs .004 grams, and that there are 1,000,000 ants per human.  Thus, the earth’s ants weigh around 21 billion tons (I didn’t try to use dry weight).

Not to be beaten by these little bugs, however, humanity is increasing its weight at a rapid rate.  Issac Asimov once (Asimov 1975) estimated that if our numbers continued to grow at the 1970′s rate of 2% (doubling in 35 years), the mass of humanity would match that of the whole planet in about 1500 years.  Probably no ants (or any other animal) could survive this.  Of course, our birth rate is declining, and even though our life expectancy is increasing, doubling our numbers will take longer and longer.  If we assume that the average human weighs 120 pounds, our species currently weighs 420 million tons.  If we double every 100 years, and if we do not destroy any ant habitat (OK, that is not a reasonable assumption.  Nevertheless…), we would weigh more than the ants in 600 years.

The photo shows Myrmecocystus navajo, a member of the Formicinae subfamily.  This one was collected in Yavapai County, Arizona.  The photo may be by Barry Bolton, but it could be by Stefan Cover or Bob Johnson.  It is from the AntWeb website.

Arizona’s premier mammal species, and one of the very youngest, the humans (Homo sapiens), congregates in urban habitats that most other mammals avoid.  Residents of the scattered human homes of the Agua Fria River Basin often see the 15 to 20 common species that are active during the day and early evening.  Residents of large urban areas such as Phoenix and Tucson rarely see more than three or four species.

Developers are eager to fill the Agua Fria River Basin with homes and businesses.  As the human population of the Basin grows, the familiar mammals will disappear.

Of course, the decline of other species as the human population grows is a global development.  When I began high school in 1960, the human population of earth totaled three billion.  Forty years later in 2000, it had doubled.  According to the U. S. Census Bureau, Earth’s human population will reach 8.5 billion by 2040.  From 1960 to 2000 the U. S. population grew from 180 million to 280 million, and will add more than 100 million during the next 25 years.

In Arizona the extinction of other species by humans is already evident for fish, but it will soon become just as obvious for mammals and other species groups.  Over the next 100 years many species will disappear.  Mass extinctions have occurred before in Earth’s history, but none were larger or more abrupt than the one that is being caused now by humans.  No other species has ever achieved such a great destruction of life on earth.

Mammals are described in numerous field guides and websites (e.g., Kays and Wilson, 2002, National Wildlife Federation, AZGDF).  Field guides often cover tracks, and some (e.g., Halfpenny 2000) are devoted to this essential subject.  A complete field guide to Arizona’s 144 mammal species can be assembled and downloaded from the North American Mammals page of the Smithsonian Institution’s National Museum of Natural History web site.  The downloaded field guide will have a page for each species with a picture, distribution map, and description.

The photograph shows a Rock Squirrel sitting on a fence post. 

Butterflies and Moths

Butterflies have always seemed to me to be friendly but too carefree to become fast friends.  A good part of their time seems to be spent simply enjoying flying.  Some of them soar and sail, never seeming to land.  Others flit from flower to flower with almost as much concentration as honeybees.  But friendly or not, butterflies are among the most familiar and beautiful animals.

Moths are closely related to butterflies, but are not as familiar because most are active only at night.  Moths are more numerous than butterflies, and most scientists believe there are at least ten times as many.  Based on new species discoveries, we can project that most moth species have not been identified

Butterflies, moths, and other bugs on the land and in the air and soil, are necessary for life on earth.  Plant pollination, down and dead recycling, and consumption and transformation of standing plants, are familiar services that bugs provide.  Without butterflies, moths, and all the other small creatures, we mammals would not last long.

The photograph shows a Mourning Cloak Butterfly (Nymphalis antiopa).  I nominate this species to become the emblematic butterfly for the Agua Fria River Basin.  The Mourning Cloak is truly at home among the willows and cottonwoods growing along the Agua Fria River in the heart of the Basin.  Mourning Cloaks mate in early spring, but I have seen adults flying beside the river on sunny days in all months of the year.

Arizona Fish

Arizona’s native fish are adapted to limited habitats, drought, and flash floods.  One or possibly two minnow-sized natives occupy the uppermost stretch of perennial water in the Agua Fria River.  Massive summer floods occur in most years.  The floods seem almost certain to sweep away the tiny fish, but after the floods ebb, I always find the little guys in their small schools in the shallow water of the main channel.  Their technique for surviving the floods is simple.  As water rises, they swim out into the slow-moving, margins of the flood amidst the grass, shrubs and trees of the floodplain. Perhaps they look forward to these summer mini-vacations.

Arizona’s fish are not adapted to human civilization.  Our most lethal attacks on the fish include:  Introducing exotic species such as carp, bass, and trout; damming and diverting streams; removing the protective vegetation of the watersheds by logging and livestock grazing, and filling the streams with toxic chemicals.  “Out of the 36 fish species native to Arizona, one species is already extinct; 34 have been identified as Species of Greatest Conservation Need in Arizona; and, 20 have been federally listed as endangered or threatened. A special and irreplaceable part of Arizona could easily disappear if more native fish species are lost” (Arizona Game and Fish Department website).

Arizona’s amphibians aren’t doing very well.  It seems that the more a species depends on water, the greater its risk of extinction.  Most of Arizona’s fish and many of its mollusks are in danger.   There is very little local data for our amphibians, but it is well documented that frogs and toads are disappearing around the world.  The causes are a ‘perfect storm’ of surface water diversion and use, water pollution, disease, and predation by invasive species.

The photograph shows a Woodhouse’s Toad, often heard crying in the woods along the Agua Fria River in Dewey-Humboldt, AZ.