Saturday, September 19, 2015

Signs of Fall

Ginseng at farm
Although signs of the fall season are usually evident enough from changes in the weather, there are many clues from nature that a seismic shift in the seasons is occurring.  Even if you did not have a calendar, you should be able to predict the month if you study the many signs that nature provides.
During a recent walk on our farm I picked up a handful of nuts from the forest floor.  Can you identify  the acorns, shagbark hickory nuts, black walnut, buckeye, hazelnut, and chinquapin?  These provide a bountiful crop for wildlife to harvest and hide away for the future.  Many such nuts are never recovered by rodents and germinate.  
Nanny berry
There are many soft fruits in the forest including this nannyberry.  It is Viburnum lentago and is one of many viburnums which produce "haw" fruit which are prized by animals of all kinds.  The variation in fruit color is interesting since it illustrates how plants communicate the ripeness of their fruits to frugivores.  It would be disadvantageous for the fruits to be eaten before they are ripe, since the seeds are not mature, so unripe fruits are often unpalatable or even poisonous. The change in color from green to red, yellow or black that signals ripeness is easily recognized and is so familiar to us that we often fail to understand the evolutionary meaning. 
 
Indian grass at farm
Grasses are also producing seeds and I here illustrate this with one of my favorites, Indiangrass.  Grasses do not have pretty flowers and they are wind pollinated so we do not always consider them to be beneficial to animals.  But the seeds are eaten by a wide variety of birds and over an extended period.  So it is important to allow grasses to flower and mature seeds in the fall and leave them in the fields during the fall and winter as wildlife food.  Grasses can also be quite beautiful at this stage of growth.
 

Shadow darner
One distinct sign of fall around our ponds is the rapid decline in insect activity and a change in the species present.  For example the large common green darner migrates south and is replaced by the similarly sized shadow darner.

Yellow legged meadowhawk
The autumn or yellow legged meadowhawk is the last dragonfly to emerge in the north and likely the last one seen before winter.  The male shown here is a beautiful red color to advertise its virility.  The appearance of odonate species that specialize in cooler conditions seems to be a classic case of avoidance of competition by a temporal shift in activity.

Tiger swallowtail caterpillar near pupation 
Eastern tiger swallowtails are a common butterfly in our area but we almost never find the caterpillars which feed on black cherry and tulip poplar. This caterpillar found its way to our porch and has changed from green to brown as it approaches the time for pupation.  It has two false eye spots which may confuse avian predators into thinking it is a scary snake.  In addition when disturbed it protrudes an osmeterium which looks very much like the tongue of a snake.   These mechanisms to avoid predation illustrate how intense the efforts of birds are to find and eat caterpillars, and how gullible birds can be when confronted by these elaborate ruses.  

Golden garden spider
When I see large golden garden spiders on their webs I know it is fall.  These spiders over-winter as eggs or young spiders and gradually grow to an adult size over the summer.  The large female builds a characteristic orb web with distinctive  zig-zag patterns called stabilimenta that strengthen the web, and may attract insects and warn birds not to fly into the web.  

Red shouldered hawk
The migration of hawks is a characteristic fall phenomenon and I recently noticed this juvenile red shouldered hawk in a tree on our farm.  The juvenile plumage pattern seems to be good camouflage and signals a lack of maturity to adult hawks.  We do not see red shouldered hawks during the breeding season so this must be a bird that is migrating south.  They make use of rising currents of warm air or thermals to minimize their energetic cost of long distance flight.

Although the arrival of fall signals the end of the growing season for most animals and plants, it is a time of many changes in the world of natural history that are of great interest.  So get out and enjoy the beauties of fall and observe how a few species wax while most others wane in abundance.

Bill Dunson Galax, VA and Englewood, FL 

Tuesday, September 15, 2015

Fwd: Bee? On fire cracker bush?

 
The message below was an answer I sent to a friend in Venice, FL, who asked me about a so-called "fire cracker" plant in his yard that was visited by bees.

 
Hi Tom-

A very nice photo and getting the bee in flight is hard!

This is not a fire cracker plant but a native firebush, Hamelia patens.  The name firecracker is usually applied to Russelia , a native of Mexico, which has somewhat similar flowers but very different leaves  ( https://en.wikipedia.org/wiki/Russelia).  

I predict that the bumblebee will not be able to drink nectar from the firebush flower without biting the base of the flower and stealing the nectar.  The corolla tube is far too long for its tongue and too narrow.  Watch the bee closely when it lands on the flower and see what it does- I predict it will go to the base of the flower tube and bite through.  I see this all the time with honeybees on Cape honeysuckle flowers, and some bees on flowers of Abelia.  

I have seen mainly zebra (longwings), gulf fritillaries and hummingbirds on flowers of firebush.  They have long and narrow tongues which can reach the base of the flower.

Firebush is the champion great bush for the yard since it provides nectar, fruit and cover for insects and birds.  It is however quite sensitive to frosts and will be frozen back if planted inland.  It is also mainly a summer bloomer.


Bill



To: wdunson@comcast.net
Sent: Saturday, September 12, 2015 10:57:20 AM
Subject: Bee? On fire cracker bush?

HI BILL
HERE IS PIC OF BEE? TOOK US SOME TIME TO GET.   CONNIE AN TOM

Sent from my Verizon 4G LTE Tablet
CONNIE AN TOM 

Wednesday, September 9, 2015

Those Beautiful Blue Flowers of Fall‏

Monarch on blue mistflower or ageratum
Although there are wide variations in flower color at all seasons, I tend to think as summer as being the time of many yellow flowers of the aster family.   Hence the derivation of the term for the many often unidentified yellow composites/ asters as "DYC," or darn yellow composites! 


Bumblebee on blue mistflower
Here in SW VA in fall we continue to have many yellow flowers such as goldenrod, but it is also the time for spectacular blue flowers, many of which are specialized for pollination by bees, especially bumblebees.  Bumblebees are physiologically adapted for foraging in cooler fall temperatures due to their ability to raise their body temperature by muscular contractions.  Thus when I go out on an early fall morning, it is cool and there are primarily bumblebees on flowers.

Yellow scape on blue mistflower
A very popular flower in the aster family for many insects in our September yard is the blue mistflower or ageratum.  It has a flat flower shape that is attractive to a wide variety of insects.  For example here are some photos of a monarch, a bumblebee and a yellow collared scape/tiger moth on mistflower.  

Lobelia
In contrast some of the lobelias in the bluebell family attract specific pollinators.  The spectacular great blue lobelia which blooms in late summer and early fall in our area is primarily pollinated by bumblebees.  Yet a close relative, the bright red cardinal flower, primarily blooms earlier and is usually pollinated by hummingbirds.


Blue monkshood

The color blue seems to be an attractant for bumblebees which may not perceive red as a distinct color.  Thus the fall-blooming blue curls (mint family) is pollinated by native bees.  The fall blooming deep blue monkshood (buttercup family) is a bumblebee specialist.  

Blue curls Trichostema
The more you learn about flowers, the more complex their structures and functions are revealed to be.  Yet there are common evolutionary themes that begin to reveal themselves when you look for patterns.  One of the more interesting is the relation between flower color, structure and the pollinator(s) for which the flowers are most attractive.  So when you go out to commune with nature don't just smell the flowers, look carefully at them and the pollinators that they attract.   

Bill Dunson 
Galax, VA and Englewood, FL 

Wednesday, September 2, 2015

Milkweed Madness

Monarch feeding on ironweed
If you manage a field, you face a conundrum in deciding your specific goals and if, when, and how often to mow.  If you want to retain the field, you must eventually mow it, but preferably no more than once per year to minimize negative effects on wildlife.  Otherwise woody vegetation will eventually move in and convert the field into a woodland. But the speed of this succession is highly variable in different locations.  

Monarchs mating at farm
Mowing more than once per year usually converts the field into short grasses which are minimally useful to wildlife.  But when do you mow?   A traditional approach is to wait until late August after all birds have nested.  This has the drawback that it disrupts the replacement of the early cool season grasses (such as fescue) by warm season grasses (which is stimulated by earlier mowing), and limits the amount of food and cover that will be in the field during the non-growing season.  Another issue is what the impact would be on milkweeds.  We have large numbers of the common milkweed, Aesclepias syriaca, and want to keep them healthy for monarch butterflies.  

You would think that mowing would be bad for milkweeds and monarchs.  I have found this not to be true because monarchs in our area primarily pass through in late summer and early fall.  By August, milkweeds which are not mowed are past blooming, are dry and senescent, and suitable as food for milkweed tussock moth caterpillars, but not monarchs.  
Milkweeds regrown in middle pasture

If the fields are mowed in mid-June to early July, the milkweeds quickly regrow and some are blooming within about 5-6 weeks.  There are then many young tender leaves suitable as food for monarch caterpillars.  The photo taken Aug. 23 shows a field mowed on July 15; some plants are blooming and there are many tender young plants.  It is likely that if open field-nesting birds such as meadowlarks are disrupted by early mowing, they will quickly re-nest.  

Black swallowtail feeding on milkweed
Adult monarchs feed on the nectar from milkweed flowers, as do other butterflies such as this female black swallowtail.  Monarchs also derive nectar from a variety of other flowers such as this ironweed.   Many such nectar sources other than milkweeds are found not in the mowed grasslands, but around the wetter edges which are mowed less frequently.  

Monarch caterpillar on common milkweed
We have found that mowing as infrequently as every 3-5 years can be effective in maintaining a bio-diverse field attractive to insects and birds.  Hand cutting of woody stems and selective mowing of problem areas with invasive infestations such as Canada thistle can help maintain these natural flower gardens as nectar sources.  Burning in late winter can sometimes also be beneficial in controlling unwanted plants and in releasing nutrients from dead plant material, depending on your goals.

Monarch on milkweed regrown from mowing
I urge you to consider the possibilities for milkweed cultivation in your local situation, either from the natural growth in fields, or plantings in your yard.  Experiment to see what works best in your circumstances.  Try cutting some plants down at different times to see if the subsequent re-growth provides a useful means of  providing better food for our marvelous monarch butterflies.

Bill Dunson 
Galax, VA and Englewood, FL