Sunday, June 28, 2015

Eggs-traordinary Bird Nests‏

Tree swallow eggs at the farm
How often do we stop and think about how amazing the bird egg is?  It is such a familiar object via the breakfast meal that we do not consider how remarkable it is that a complex organism can develop within such a closed structure.  Indeed the evolution of the most specialized type of "cleidoic" egg, which exchanges only gases with the surroundings, was one of the developments that enabled the full colonization of dry land by vertebrates.

Catbird nest at the farm
Aside from the their remarkable physiology, bird eggs and nests are simply beautiful expressions of the adaptations of each species.   We have the opportunity to enjoy them by observing them in our yards, being very careful to minimize disturbance.  One advantage of locating nests is to subsequently protect them from undue disturbance.  

Redwing nest at Virginia farm pond
By watching the movements of birds within a 100 foot radius of our house and examining all dense bushes and small trees I have been able to find nests of 16 species (Baltimore and orchard orioles, mourning dove, house finch, barn and tree swallows, phoebe, robin, Carolina and house wrens, bluebird, mockingbird, catbird, willow flycatcher, blue grosbeak and redwing).  

Mourning dove nest at Virginia farm
Certainly I have missed many (for example yellow throated vireo) that are too high to see, some that are in dense grasses (common yellow throat, meadowlark, song, savannah and grasshopper sparrows) or some that are just very secretive and have simply eluded me (brown thrasher and yellow warbler). 

Carolina wren eggs in carport
The colors of eggs in our yard can be roughly divided into those that are all white, all blue, and a mixture of speckles and streaks with variable ground colors.  In some cases the colors would seem to enhance camouflage and in other cases there is no obvious reason for the color and pattern.  For example white eggs which would seem to be the most obvious to predators are found both in mourning doves, which have a simple open nest of sticks and grass, and tree swallows which nest in dark, protected tree holes (or nest boxes).  

Mockingbird nest eggs in apple tree
Eggs that are streaked or speckled would seem to be the best camouflaged and are found in the open nests of redwings, willow flycatchers, and mockingbirds. But Carolina wrens which nest in less exposed situations also have speckled eggs.  

Robin's nest in Maresii viburnum
Sky blue eggs are typical of robins and catbirds which both make open nests of grasses.  What would be the purpose of this color?  Thrushes (robins and bluebirds) tend to have all blue eggs; the mimid catbird is similar whereas the mockingbird is bluish with dark speckles.

Willow flycatcher nest at the farm
Truly bird eggs are beautiful, fascinating and enigmatic!  So enjoy the hunt for bird nests in your yard, protect them from disturbance, and thrill in the remarkable process of avian reproduction.  Life is certainly grand, but it can use a hand from us in ensuring that our birds and their progeny will thrive and return next year.

Bill Dunson 
Galax, VA and Englewood, FL

Stump Pass dredging plan‏

In today's Englewood Sun Herald there is an article about the upcoming dredging of Stump Pass that is slated to start this coming November.

This was the diagram depicting the combined dredging and proposed installation of groins or jetties.   Sorry that the quality is poor but you can get the idea. The placement of jetties on the north and south side of the pass is entirely new and has the potential for vast changes, namely a loss in sand on the southern side of the pass.  So for those of us with property on Palm Island south this could be big trouble.

There is a considerable literature on the well known effect of sand starvation of islands lying to the south of jetties that stop the north to south flow of sand.  I will attach a photo of one such well known example from Ocean City MD where the jetties caused a huge loss of sand from the northern end of Assateague Island.

Cheers- Bill

Thursday, June 18, 2015

Creek side monster‏

My son David and grandson Peter were walking along the New River Trail that borders Chestnut Creek in Galax, VA, when they spotted a huge and interesting bug.  This was a real whopper and very scary looking since it seemed to have massive and dangerous jaws.  But I recognized it as a harmless male dobsonfly, which is the adult form of the aquatic hellgrammite, familiar to fishermen as a good bait for smallmouth bass.  The larvae are fierce aquatic predators for two to five years and then metamorphose and emerge from the water for only a few days to breed, but do not feed at all.   The spectacular jaws of the male are used to joust with other males and possibly to grasp the females for mating. They are related to fish flies and alder flies and are usually placed in a group called the Megaloptera.  They are found widely in the eastern US from Canada to Florida and Mexico.  Yet very few people have seen the reclusive larvae and ephemeral adults.  So put it on your bucket list to discover the remarkable dobsonfly.

Tuesday, June 16, 2015

Fast Food for Snakes- the Avian Nest Box‏

Bird house at farm
Humans delight in trying to improve the lives of our beloved birds, but sometimes this can go horribly wrong.  A case in point is the nest box which is erected for hole nesting species such as bluebirds and tree swallows.  The easiest way to erect a box is just to attach it to a post or tree.  However this has a huge downside in that it provides no protection against climbing predators such as raccoons and snakes. 

Black rat snake in birdhouse
One result of my being lazy and not providing predator protection for a small number of our nest boxes was revealed recently when I suddenly noticed a snake head protruding from a nest box I had simply screwed to a post holding up my wood shed roof.  A large black rat snake had climbed up or down the pole and crawled into the box.  I believe that this brood of tree swallows had left already and were safe.  However our other boxes still have young birds in them and would be at risk if not protected.  Indeed the black rat snakes in our area seem to be almost entirely bird eaters and refuse to eat mice and rats in captivity.

I am a huge fan of reptiles and in fact previously taught a course in herpetology.  Thus I certainly am happy to see snakes and believe in allowing nature to take its course. Snakes must eat  and they just happen to be predators as are many humans.  But it upsets my wife to see this happening on our land so I remove and transplant any snakes we find on our farm near the house.  

One solution is to place stove pipe baffles on all nest boxes which are erected on metal pipes. This will protect from all but aerial predators. So I urge you to be responsible landlords of your nest boxes and protect them as well as possible from predation.  I also urge you to resist irrational fears of snakes which may be rooted in religious myths and possibly also in the response of early humans to the unusual shape of snakes (which can be considered phallic symbols) and their unusual ability to shed their skin intact. 

Tree swallow nestlings in bird box
 Although we all have our irrational fears, they can be no ecological justification for selecting out certain groups of animals for persecution.  Let us strive to live in harmony with all of nature and impact it as little as possible.
Black rat snake eats young tree swallow

Bill Dunson 
Galax, VA and Englewood, FL 

Monday, June 8, 2015

Avian Delights of Early Summer‏

Baltimore oriole
Along with the warming temperatures, the greening of the landscape, and the blooming wildflowers, the songs and colors of birds are one of the intense delights of the spring and summer.  As I write this on June 7, some birds have raised one brood already (bluebirds, mourning doves, tree swallows, robins, meadowlarks) whereas others are in the process of rearing young (Baltimore and orchard orioles) or still sitting on eggs (catbirds) or still making nests (willow flycatchers). 

Tree swallows nest in many of our 25 nest boxes (a male is shown here on top of one) and are constantly flying around our yard and ponds.  The back of the male alternates between appearing bright blue or green depending on the angle of the light since this is a structural color without any pigment involved.  They are dominant over bluebirds competing for the same boxes but the bluebirds manage by producing more broods and starting earlier.

Orchard oriole on red hot pokers
We have Baltimore and orchard orioles nesting in the same large maple tree in our front yard.  It is interesting that they seem not to squabble over territory, perhaps because their preferred habitats and diet are only partially overlapping.
The orchard oriole is unusual in that it is specialized for collection of flower nectar including the piercing of the base of larger flowers or those with long corolla tubes.  This photo shows a male orchard oriole perched on the flower stems of red hot pokers from which it has been drinking nectar.  

A most unusual and the largest of the woodwarblers is the yellow breasted chat.  It is found primarily in early successional habitats and thus must move frequently to find new nesting sites.  The seven acre field where this and another chat were singing was clearcut three years ago and is now filled with shrubs.  This is a poster bird for the advantage of making clearcuts in some but by no means all forest habitat.  Maximizing biodiversity requires a maximum heterogeneity in habitats, a fact that all land managers need to recognize.    

Grasshopper sparrow
The grasshopper sparrow is a bird that requires open grassland breeding habitat, and is thus often found in cattle pastures.  Before the advent of humans, one wonders how many short grass prairies would have been available to them.

The pileated woodpecker would have fared well in the unbroken forests that covered much of the eastern US before the advent of humans.  This male returns regularly to a rotting stump in our front yard to chop away in its hunt for wood grubs.

Canada Geese
One bird I do not encourage to linger around our ponds is the Canadian goose.  This adult with young goslings in tow is a cute picture, but bad ecology.  These geese should be breeding far to the north but individuals that were originally wing clipped and allowed to breed far south of their normal range have become established as transplants.  They foul the shores of their new homes in yards and golf courses and can be aggressive in defense of their young.    

Solitary sandpiper
Two wetland species that I am very happy to see in our yard are the spotted and solitary sandpipers.  It is interesting to see spotted sandpipers with their breeding plumage with a spotted breast.  This is one breeding season transformation that does not make much sense since the male and female are identical and the transition does not seem to affect their visibility to predators.  They breed locally along river banks.  In contrast solitary sandpipers pass through our yard every year on their way to breeding grounds in Canada.  

Spotted sandpiper
I highly recommend leaving your bedroom windows open at night so that you can hear the early morning chorus of the birds that will thrill your heart.  Learn the common songs and follow the movements and breeding of your favorites.  This time of year is one of the highlights for those who enjoy birds and each of us only has a limited number of such opportunities, so do not let them slip by without enjoying them to the max.

Bill Dunson 
Galax, VA and Englewood, FL