Impale before eating

The concrete felt cold beneath me.  I’d sat on its frozen surface for more than an hour.  Thankfully warm winter sun fell on me and heated the dark colors I’d chosen to wear (smartly so I might add, for the temperature never rose above freezing—or for that matter, it never came to within five degrees of freezing).  Yet the harsh chair that threatened to numb my bottom with chill and discomfort couldn’t make me leave.

A tiny motte near the sidewalk offered something worth seeing.  Or at least something worth trying to see.  Hunting the frozen ground and using the bare branches to survey the area for prey, a loggerhead shrike (Lanius ludovicianus) flitted through a ligneous maze, dashing to bare earth and back again as it looked for breakfast.

Not large birds by any stretch of the imagination, shrikes have chutzpah that leaves mouths agape.  I watched one once as it tried to drown a killdeer (Charadrius vociferus).  It should be noted that a killdeer weighs twice as much as a shrike.  How the small killer thought it would carry away the larger bird had it succeeded in drowning it I will never know.  But it didn’t succeed: the poor killdeer took a beating before making good its escape.  (Several times I thought the shrike held the plover underwater long enough to win the battle, but the killdeer showed impressive stamina coupled with a very strong will to survive.)

On this particular morning, however, killdeer was not on the menu.  The shrike hunted in a small stand of trees alongside a road, traffic separating us from a neighborhood just across the way and a vast meadow of prairie grasses laid out on the other three sides.  The golden field hid pipits and meadowlarks, the occasional harrier sweeping across low to the ground and kestrels perched conspicuously throughout the area.  Bluebirds, crows, hawks, woodpeckers and sapsuckers, herons, ducks, sparrows, chickadees and titmice…  I had difficulty keeping track of all the species.  And though so much life bubbled and percolated no matter where I looked, I played the part of a stone as I watched the shrike.

Despite never having an unobstructed scene, I figured it best not to move.  The shrike didn’t seem to mind me so long as I sat still, so at least I could watch as it went on with its hunt.  The predator eventually dropped to the ground for a split second, grabbed something, and returned to the branches with its prey.  That’s when it showed a behavior that often leads to bizarre collections of critters hung like drying laundry.

A loggerhead shrike (Lanius ludovicianus) impaling an insect larva on a tree branch (2010_01_12_048268)

Shrikes are known for impaling their prey.  Sometimes they leave the food impaled and come back to it later; sometimes they impale it to subdue it, then they eat it immediately.  Amazingly, toxic prey such as poisonous frogs and grasshoppers are left impaled for days at a time before being consumed, a practice thought to dissipate the noxious chemicals.  (And for some toxic species, the shrikes will only consume the parts that do not contain the offensive substance.)  But no matter the varied reasons behind the practice, this bird offered a quick glimpse of how determined they can be about it.

The larva it held found itself quickly pressed against a tiny sprout on the branch.  The shrike ensured it ran the insect right through, pushing and manipulating the meal until it could be pushed no further.  Then it pulled the grub off the branch.  I thought that would be the end of it.  But not so fast!

A loggerhead shrike (Lanius ludovicianus) preparing to impale an insect larva on a tree branch for the second time (2010_01_12_048290)

With entrails dangling from the prey, the shrike moved to a different branch, positioned itself facing me, and then proceeded to impale breakfast on another branch.  The larva nearly split asunder at that point.  The job apparently done, the shrike slipped the food from the tree and flew across the street to a brick fence.  It landed there and enjoyed its catch.

I remained seated for some time longer hoping the shrike would return to the motte.  It regrettably had other plans.  After dining, it sat on the brick fence for a few minutes before flying in the opposite direction through the neighborhood opposite the park.

[photos taken at Plano’s Oak Point Park and Nature Preserve; a grateful tip o’ the hat to Amber for telling me about the place because it made for a succulent diversion from my usual haunts]

Not an insect

Call them pill bugs, sow bugs, roly-polies or whatever else you want to call them, but one thing is true about woodlice: they’re not insects.  Actually they’re isopods, a type of crustacean.  They’re related to shrimps, crabs and lobsters.

A woodlouse (Porcellionides pruinosus) running across my patio fence (20080913_11936)

This woodlouse is Porcellionides pruinosus.  I found the little critter scampering across my patio fence.  Poor thing.  Though it might not be obvious in these photos, I’d say this woodlouse got beat up.  It was missing several pieces and parts.  Still, it seemed to be doing just fine because it ran along the fence at great speed

A woodlouse (Porcellionides pruinosus) running across my patio fence (20080913_11934)

With the weather turning much cooler today, I’m sure it already found a new spot where it can stay cozy for a few days.  Amazing how much life jumps at the opportunity to move about as soon the sun comes out or temperatures climb above freezing…

‘The birding community’ hates birds: Pishing and Tape-Luring – Part 2

Energy cost, increased conspecific and intraspecific confrontations and interactions, and disruption of normal activity.  These mean one thing: forced stress and aggression.  That represents the combined general impact on individual birds when they respond to pishing or tape-luring.  Any call used to bring birds out of hiding must elicit the same natural responses that would coincide with the call were it issued by another bird.  For example, alarm calls must produce stress and aggression along with the correlative hormones that define those states.  A challenger call would likewise produce the same physiological response.  In truth, any call utilized must produce a physiological response in every bird that hears it regardless of whether or not they respond to it in person, and those who do respond to it must likewise take part in a compulsory meeting with other birds who respond.  That is a meeting we can scarcely predict or control.  Also, birds reacting to the calls must expend energy and must stop engaging in natural behavior in order to respond.  So let us then turn to the existing science with hope of understanding how these practices can produce, in Professor Daniel J. Mennill’s words, “longlasting and far-reaching effects on individual fitness.”

Paulo G.  Mota and Violaine  Depraz, both from the Laboratory of Ethology, Institute of Environment and Life, Department of Anthropology, University of Coimbra at Coimbra, Portugal, published a paper entitled A Test of the Effect of Male Song on Female Nesting Behaviour in the Serin (Serinus serinus): a Field Playback Experiment.  In it they said “[i]t is well established, through laboratory experiments, that male song in birds can stimulate female reproductive activity, affecting their behaviour and physiology, such as follicular growth, nest building and egg-laying.”  Simple extrapolation based on everything we know about wildlife biology broadens that statement to mean a bird responding to a call demonstrates a physiological effect, whether it be fear in the nest, mobbing a predator, establishing a relationship, pair bonding with a mate, feeding offspring, investigating a threat, competing with a challenger, or any of a seemingly endless number of other purposes.

(Only humans have demonstrable capabilities for rendering communication as an empty gibbering without societal, relational or survival meaning.  If you’ve ever suffered through a tedious dinner party conversation or listened to someone speak ad nauseam about nothing, you know precisely what I mean.  In nature, however, communication always has purpose, a reason we might or might not understand, and its use as a meaningful and never-empty tool is established by more studies and science than can be contained in this series.  Please feel free to investigate that on your own if you wish.  You might start with this list of bird communication research and this list of animal communication research, both provided by Cornell University.)

Given that bird communication always means something and such communication requires some kind of physiological response, let me turn your attention to this: testosterone.  The word elicits the mental image of male virility, strength and fitness.  In the strict sense of physiology, testosterone is a steroid hormone and the most powerful natural androgen.  While usually tasked with regulating secondary male sexual characteristics such as body hair and musculature, it also occurs naturally in both genders as a response to stress, at which time it acts as an amplifier for strength and endurance, most notably as a result of duress.  I also point out that it increases aggressive tendencies.  (This is all basic physiology.  I encourage you to research testosterone independently if you would like a more detailed understanding.)

In their paper “Avoiding the ‘Costs’ of Testosterone: Ecological Bases of Hormone-Behavior Interactions”, John C. Wingfield and Sharon E. Lynn from the Department of Zoology, University of Washington at Seattle, and Kiran K. Soma from the Department of Physiological Science, University of California at Los Angeles, begin with this:

A combination of laboratory and field investigations of birds has shown that expression of behavior such as territorial aggression can occur throughout the year in many species and in different life history stages.  Although it is well known that testosterone regulates territorial aggression in males during the breeding season, the correlation of plasma testosterone and aggression appears to be limited to periods of social instability when a male is challenged for his territory by another male, or when mate-guarding a sexually receptive female.

Thus they explain the two common times when testosterone levels are greatest in birds: during challenges and in the breeding season.  This seems to have little to do with pishing and tape-luring though, given the specific times when the hormone level is highest.  But the study goes on to address high testosterone levels outside those two naturally occurring “high tides”:

How essentially identical aggression is modulated in non-breeding life history stages is not fully resolved, but despite low circulating levels of testosterone outside the breeding season, expression of territorial aggression does appear to be dependent upon aromatization of testosterone and an estrogen receptor-mediated mechanism.  There is accumulating evidence that prolonged high levels of circulating testosterone may incur costs that may potentially reduce lifetime fitness.  These include interference with paternal care, exposure to predators, increased risk of injury, loss of fat stores and possibly impaired immune system function and oncogenic effects [causing tumors].

In a separate study (PDF) entitled “Reproductive Endocrinology of the Song Wren (Cyphorhinus pheaeocephalus), A Resident Bird of the Lowland Tropics,” Dr. Wingfield and coauthor D. S. Busch more specifically say that “[i]n many avian species, using conspecific playback to simulate a territorial intrusion results in an increase in LH [Luteinizing hormone] and T [testosterone] in the territorial male.”  (One must accept as part of this finding that pishing causes the same result because it elicits a territorial and/or mobbing response, though I will certainly entertain corrections on that should someone be able to demonstrate forms of pishing that do not rely on challenger, predator, alarm or other stress-inducing calls.)

A disturbing aspect of elevated testosterone levels comes to light in “The Effects of Experimentally Elevated Testosterone on Parental Care in Female Dark-Eyed Juncos” (see previous PDF) by D.M. O’Neal, K. Pavlis and E.D. Ketterson (Indiana University, Bloomington, and University of Guelph).  The research begins by reiterating a previous study on male dark-eyed juncos which found heightened testosterone levels decreased parental care by the adults.  The scientists then performed a similar study on females of the species and discovered those with elevated levels of the hormone “showed a significant reduction in the number of nestlings fed per hour and in overall provisioning rate as compared to controls,” and they also realized the females “exhibited less nest defense than control females, and their nests were more likely to be lost to predators.”  Keep in mind this is only due to the hormonal effects and not the generalized issue of being called away from a nest and/or young.

But stressor responses involve more than testosterone.  Other hormones are involved in addition to physiological impacts outside those referred to above.  An interesting piece of the puzzle comes from an unexpected source: “Why Does Stress Suppress Immunity? A Possible Answer From Insects.” (see previous PDF) by S.A. Adamo and N. Parsons from Dalhousie University.  “Both vertebrates and mollusks (e.g. oysters) become more susceptible to disease after exposure to a stressor, suggesting that stress-induced immunosuppression is an old and wide spread phenomenon. […] Wound infection was more likely after restraint stress than in controls.  Preliminary evidence suggests that the decline in immune function after stress is due to a physiological constraint involving carrier molecules (lipophorins) that are required both for ferrying lipid energy compounds from fat body to muscle as well as for normal immune function.”

This presents an interesting point.  It obviously would behoove birders not to use either method in the presence of a wounded, ill, aged or otherwise susceptible individual.  But how can one know when one or more weak individual birds are present before pishing or tape-luring?  The answer is simple: one can’t know.

Lest we worry too much about stress and testosterone, however, allow me to focus on that “fat body to muscle” statement in the aforementioned study.  When is fat most needed?  Is it winter when food is scarce and energy reserves important, and temperatures low enough to require additional insulation?  Is it spring and autumn when sufficient energy for migration is a must?—

Wait!  What about nonmigratory birds?  I know that question dwells heavily in the ether.  Though the energy needs and constraints remain predictable for such species in the breeding and winter seasons, they face a different challenge in autumn and spring when migrants fill the air.  That challenge is called increased competition.  Nonmigratory birds must react to interlopers with the same vigor and stamina with which they would react to threats or challengers.  In fact, additional threats and challengers fly through with every migratory bird, whether that be hawks or flycatchers or vireos or gulls.  The underlying reasons for energy conservation may change for nonmigratory species during migration seasons, but the need for energy conservation does not change.

—Or is it the breeding season when mate guarding, protecting a nest and its eggs, and brooding and rearing young must be paramount?  Or is it competing for social status in nonbreeding seasons when science already has shown females are more likely to change mating and parental decisions based on male success?  Or more troubling, is it all of the above?  The answer is all of the above.  Birds do not watch television, they do not read books, they do not know of boardgames, and they have no comprehension of things like long walks after dark or endless conversations around the dinner table.  No, birds know of one thing that rests at the crux of their existence: survival.  This includes foraging, staying warm, migrating, nesting and brooding and caring for young, wooing a partner and mating, fighting predators and challengers and responding to threats, and otherwise focusing on ensuring fitness for procreation.

The question of asking—No, not asking.  That’s the wrong word.  Pishing and tape-luring are certainly not requests.—The question of demanding a bird respond and show itself due to calling boils down to forcing the bird to expend energy.  Even researchers cannot know when that energy is abundant or in short supply unless they capture and examine the bird(s).  Even researchers understand that current and previous environmental conditions coupled with individual fitness plays a role in a chaotic system where assumptions can be fatal and the truth rests somewhere beyond our reach.  Even researches know that the health and condition of birds lies hidden even to the expert observer.  As a matter of fact, even researches know that the impact of eliciting a response has untold and unknown repercussions on individual fitness, on mating, on physiology, and on health.  This begs the question of precisely whose interest is being focused upon when birders utilize these methods simply because they want to see a species.  Outside of scientific and research purposes, that’s an important consideration.

Which leads me to Mike Burrell, a researcher in the Faculty of Forestry, Earth Sciences Centre, University of Toronto, and an avid and respected birder.  When asked about pishing and tape-luring as means to see a bird, he responded with this:

As far as bird song playback goes.  It certainly stresses a bird. But, so does pishing, squeaking, etc.  The difference between playing bird song for photography and pishing is that pishing might stress a bird for a few seconds, while playing a song would probably be for several minutes.  I think that season doesn’t really matter, you are stressing the bird no matter the time of year.  What does matter to me is basically that the bird isn’t repeatedly stressed.  For example, I wouldn’t play a tape for a bird at Point Pelee in spring, but playing a tape for a Yellow Warbler in your local park once a season is reasonable.  Again, if you pay attention to the bird, you should be able to tell you are stressing it.  In all reality I think anyone who wants to play recordings should ask themselves if one person getting a photo of a bird is worth causing it stress.  Doing bird research obviously has a purpose which we weigh as more important than the possible consequences of your actions.  If birders are educated about the bird, they will make good decisions…

Good decisions…  Therein lies the problem.  Mike speaks of feeling comfortable with pishing and/or tape-luring with certain species in certain places despite admitting that both practices cause unnecessary stress.  Why?  Does he always know when and where the greatest impact will be?  Does he have some insight into the possible strains these birds are already facing when a birder shows up and begins forcing the avifauna to respond?  Does he assume or know outright what other activities have affected the birds when he recommends these practices as acceptable?  The answer is clear: No.  A resounding “no” in fact.

The inquiries already circle like moths to a flame: How much pishing and tape-luring is too much?  If a lone birder enters an area where few visit, what harm is done by utilizing these methods?  Assuming one is new to an area, how can it be dangerous to implement these lures?  Since one cannot know the individual health or disposition of any bird in the area, why is it not safe to assume that pishing them from cover and tape-luring them from their hideouts aren’t judicious methods by which to see a bird that otherwise would go unnoticed?

It boils down to this: Why would a birder inflict known stress, energy consumption, forced confrontations and possible harm simply because they want to see a bird?  What are they really concerned about: the health and well-being of the birds or their ability to see them?  I can’t answer these questions; only “thye birding community” can.  In cases of research, one can stride across those inferred boundaries with relative ease and reason.  Yet when it comes to personal fulfillment, the really important answers are not mine to proffer.  Is it about the birds or the birder?  That’s the question that counts.

But I can tell you that the impacts from these practices go well beyond part 1 and part 2 of this series, well beyond interference in social structures and well beyond individual health, well beyond influencing and manipulating pairs and parents and relationships, well beyond irrefutable harm to the ill and infirm, and well beyond the damage to bodies belonging to those who are just trying to survive.  I will explore yet another documented threat in part 3: increased predation.  And you’ll be surprised to learn it extends far beyond adult birds who respond to calls.

Part 1

[cross-posted to The Clade; of special interest is that many of the bird-related studies indicate that the stress-induced release of testosterone becomes more pronounced in species living in temperate and arctic areas as opposed to those living in tropical areas; that begs the question of where the majority of birding takes place]

Walking with spiders – Part 3

Beginning in late summer and lasting until early winter, exploring the woods and woodland edges around White Rock Lake demands a certain sense of awareness and keen observation well beyond the norm.  Why?  Imagine a spider’s web anchored by a line up to 15 feet/five meters long, an orb more than two feet/60 centimeters wide, and a rather large arachnid hanging head-down in the middle.  Now imagine having such webs clustered together where every few feet another spider hangs, each one staggered horizontally and vertically in a way that creates an obstacle course made from silk.  That describes the peak season of barn spiders (Neoscona crucifera).


In some places, up to half a dozen of these creatures can occupy an area of about ten paces.  Some build webs so high that the only sign of them is an anchor line that rises toward the heavens.  Others build webs at about face level with anchor lines running some distance away.  It’s easy to look at the amount of silk and the length of the anchors with a feeling of awe coupled with confusion: how does the spider cover that much distance in order to build such a massive web?  No matter how they do it, they certainly do it well.

The more interesting aspect of this species comes from how variable they are.  It’s not just polychroism (variations in colors), but it’s also full polymorphism (variations in colors and patterns).  Pattern differences often are more subtle than color differences, though running across one that lacks nearly any pattern whatsoever means scratching my head and wondering if I’m looking at another species altogether.

A female barn spider (Neoscona crucifera) hanging on her web (2009_09_27_029782)

N. crucifera is often confused with the spotted orbweaver (a.k.a. cross spider or redfemured spotted orbweaver; Neoscona domiciliorum).  In fact, even I’ve seen barn spiders that were dark enough to be nearly identical to spotted orbweavers save a few minor differences.  In such cases, assuming I can’t tell by size (of the web and the spider), all I can do is note that the spider is one of the two.  (Barn spiders are larger than spotted orbweavers; the former also builds larger webs than the latter.)

A female barn spider (Neoscona crucifera) hanging on her web (2009_10_10_031201)

On the other hand, I’ve seen barn spiders that lacked nearly all markings and the usual colors.  Again in these cases, I’m left scratching my head and later performing diligent research with hope of putting a name with the face.  I often am surprised to discover it’s yet another variation of the same arachnid.  (Of special note is that northern populations of Neoscona crucifera can produce a white variation in females.)

A female barn spider (Neoscona crucifera) hanging on her web (2009_11_08_037657)

By the middle of autumn, a rapid change starts to appear: a change in shape.  Once round and plump abdomens full of eggs suddenly become flat and deflated.  The spiders take on the impression of ending.  Though they can live until the first freeze—and many do—the creation of the egg sac leaves the arachnid a shadow of its former self, an almost weak-looking thing compared to its previous size.

A female barn spider (Neoscona crucifera) resting on dead leaves (2009_11_28_042721)

I admit to an abundance of confusion in the guides and resources used for differentiating these two species.  Certain diagnostic markers given for one actually match some of the broad variations in the other.  The safest way to tell the difference in places where their territories overlap and a specimen matches both species is to use a microscope to look at the female’s genitalia, or to locate and identify the orientation of a very specific indentation on the carapace (this marker is essentially impossible to see in the field except under very specific circumstances and lighting).

Thankfully in my case, all the individuals, though varied, lacked any true resemblance to N. domiciliorum.  Then again, were one to take the guidance on colors and patterns as definitive, then several of them didn’t match N. crucifera either.  What I’ve seen in researching them is a growing body of evidence which indicates a level of polymorphism similar to cricket frogs.

[all photos are of females]