The Call of the . . .

      Last Wednesday, April 18, a group of sixth grade students from McIntyre Elementary School were exploring ecosystems with me.  As we left the deciduous forest and passed by the Lower Lake, we heard a trilling sound.  (It sounded like this: http://www.youtube.com/watch?v=mA5sTqGis4A&feature=related )  I love to ask students what they think that sound is.  They guessed birds, crickets, cicadas, and squirrels.  When they learn what it is, they are just as surprised as I was when I learned this sound 20+ years ago


American Toad by Jason Sturnor 72



     This is the male American Toad.  Most people have had some contact with toads.  They are not very fast, so kids can catch them, and they don't bite (since they don't have teeth).  They will venture quite far from the water where they are born and can often be found near homes and gardens.

     Toads are great for teaching about defense mechanisms, or adaptations that enable an animal to survive its predators.  When toads are picked up by predators, children, or environmental educators, they are likely to urinate.  Although it does not discourage environmental educators, a lot of children will subsequently put the toad down so they can wipe their hand off.  Predators, I'm sure, have an even more pronounced reaction, since they have often picked the toad up with their mouth. 

     Toads have a few more tricks up their proverbial sleeve, though.  They can puff themselves up so they are harder to swallow and they excrete a foul-tasting toxin through their skin.  The large parotoid gland behind each eye secretes a powerful steroid that will affect a predators heart, so biting into a toad can be a dangerous undertaking.  Don't overlook their twist on one of the most common adaptations:  camouflage.  A little close observation of toads in various habitats will show you that they are camouflaged to their surroundings, but what happens if they change surroundings. . .THEY CHANGE COLOR!
     We have a toad that lives near our back porch at my home.  She is usually a light brown color that enables her to blend in well with the soil near our house.  Two years ago, though, she decided to hide under the black bag of charcoal beside our grill.  When I lifted up the bag of charcoal, I found a black toad!  It was our same neighborhood toad, but her body color had adjusted to her surroundings.  I don't know how long it takes for toads to change their color - they are certainly not chameleons - but they are able to change their skin color to fit in with the color around them.
     It at all possible, please take some time in the next week or so and go to a pond at night.  Listen for the call of the male toads.  Take your flashlight and quietly sneak up to the edge of the pond.  Maybe you will see a male inflating the air sac under his chin and courting a female.  You may see the larger females in the shallows of the pond responding to the calls of the males or the twisted strands of eggs that they have laid.  No matter what, it will be a special night.  There is nothing like the call of an American toad.

A Tale of Two Birds



Photo by Dendroica cerulea

    This morning I saw this bird on the deck outside my office at Lutherlyn's nature center.  It is a male brown-headed cowbird (Molothrus ater).  I have a love/hate relationship with these birds.  Actually, its more of a respect/derision relationship.  If you are familiar with the brown-headed cowbird, then I imagine that you understand why I have such a range of emotions associated with a robin-sized blackbird.
  I find the appearance of this bird striking because its black plumage has an iridescence that catches the eye, yet it has a brown head. (To me, the bird appears to be a strange hybrid of a blackbird and a female rufous-sided towhee.)
  The respect part of the equation comes from knowledge of its adaptations.  Brown-headed cowbird lived for centuries on the Great Plains following the bison herds.  These birds lived off of the insects that the bison kicked up as they grazed.  Since bison herds didn't stay in one location for very long, the cowbirds didn't have time to raise their young before the herd moved on.  A unique, if lazy, adaptation enabled them to survive - the cowbird females laid their eggs in the nests of other birds.  So all cowbirds have been raised by surrogate moms, often to the detriment of the host's young, as young cowbirds are very aggressive and will often out-compete their foster siblings.
   As the bison herds disappeared, the cowbirds had to adapt once again.  This time they moved east and started occupying the newly cleared farmlands of the eastern U.S.  They no longer had to follow bison herds and had the time to raise their own young - but now they encountered other bird species who were not familiar with their parasitic ways and did a fine job of raising their children for them - so why change?


male Scarlet Tanager

    I imagine that you can now see where the feeling of derision comes into play.  Let me introduce you to the brightest bird in our forest:  the male scarlet tanager (Piranga olivacea).  This bird travels from South America to reproduce in the mature oak forest of Pennsylvania.  In fact, 19% of all the scarlet tanagers in the world nest in PA and spend their summer eating lots of our insects.
  However, tanager numbers are declining and have been for some time.  One of the culprits is the brown-headed cowbird.  Its parasitic ways are causing more scarlet tanagers to spend their summers raising cowbird young - and the tanager's don't even seem to realize it.
   In the end, the blame can not be placed on the cowbirds, though.  Scarlet tanagers like to nest in deep forest habitats and cowbirds are usually only on the edge of forests.  However, as people continue to carve up our mature forests for homes, logging, and shale gas development, they are exposing the tanager's habitat to cowbirds.
  So, my derision is misplaced, as the cowbirds would not be able to reach the tanagers, if our mature forests were kept intact.  Indeed this is yet another example of how everything in creation is intricately connected - and how easy it is for people to unwittingly throw off the delicate balance that was meant to be.