Thursday, May 28, 2015

Bluebird Victims


The scene above is one to warm the heart of anyone tending to bluebird nest boxes.  Watching them grow and fledge is the rewarding part of maintaining and cleaning the boxes over the year.  Unfortunately it doesn't always have a happy ending as reported by Mort Shurtz.
"I've been watching our bluebird house for several weeks. First eggs, then a check on the healthy chicks yesterday and everything looked good. This morning I discovered a House Sparrow on the bluebird box. When I inspected the box, all the chicks were gone and the sparrows had built a huge nest in the box. The babies were lying on the ground about 10 feet from the box with holes pecked in their heads"
Mort's Bluebird s- day one
After the attack
The House Sparrow (HOSP) is a native of Europe and Asia which has been transported to Africa, North and South America and Australia, making it the most common bird in the world.  Native species haven't learned to compete with them as they have only been exposed to this threat for a few hundred years.  HOSP thrives in close association with humans which, come to think of it, are also a rather invasive species.

HOSP are common nest predators of small cavity nesting species such as Eastern Bluebirds.  They will peck at the head and eyes, killing chicks and adults alike.  They will also destroy and remove eggs before building their own nest.  I asked Lisa Berger from GOAS* to comment.
"House Sparrows are fierce, nasty competition, negatively affecting many native cavity nesting species.  Bluebirds, Chickadees, Titmice, Tree Swallows, Carolina Wrens, House Wrens, Downy Woodpeckers and others did not evolve with the House Sparrow on the North American continent. The English Sparrow (House Sparrow) was introduced in the new world, soon after European contact: It is, in fact, an invasive species and should be treated as such. Our native NA species do not have strategies (nor have had time to adapt) to compete favorably with invasive species."
Like starlings, HOSP are not protected by the Migratory Bird Treaty Act, which makes it illegal to harm or harass any native species, including their nests and eggs.  For this reason, it is acceptable and even encouraged to remove the nests of HOSP if you are sure that it is the offending species.  Chickadees, wrens and others should be left alone, a nice byproduct of your nest box generosity.  Charley Burwick added this advice:
"On the GOAS Bluebird trails where we have had this problem, we just remove the boxes from the routes. Typically this happens when the Eastern Bluebirds build nests in a too urban area, and the House Sparrows are plentiful. Usually, when we have ran into this issue in more rural areas, it is where there are livestock pens, etc., too close to the boxes." 


*GOAS is Greater Ozarks Audubon Society

Nestwatch.org has some practical measures to discourage sparrows from nesting in birdhouses.

Sialis.org has lots of reports of nest predation by HOSP.  Graphic pictures of the results of a HOSP attacking a tree swallow nest, not for the faint-hearted, are at this Sialis.org link.
 

Tuesday, May 26, 2015

Firefly Larva


I found this creature on decaying wood, hidden among a crop of jelly ear mushrooms I was collecting.  Although it looks like a dinosaur or a flattened crocodile, the tee-shirt fabric it is crawling on gives away its size, only 3/8" long.

I initially thought it was a sow bug, one of the flattened cousins of the familiar pill bug, both members of the wood louse family.  When disturbed it curled into a defensive ball, a poor imitation of a "roly-poly bug" from my childhood.  After wasting time trying to identify it, I sent it to Bugguide and within minutes received this response, identifying it as a Photuris larva.  Photuris is a genus in the Lampyridae or firefly family.

The common perception of fireflies is romantic, the flickering lights in the dark summer night, as the blinking male looks for muted signals from lady fireflies perched on the grass below.  That evening is just the dramatic finale to a hard life as both predator and prey.

After emerging from an egg, all lamprid (firefly) larvae are predatory, primarily eating juicy slugs, snails and earthworms as well as small insects.  They have mandibles with small channels that inject chemicals that will paralyze and kill their prey, then liquify them for digestion.  What the final adult eats aside from tree sap is unknown and some adult species probably don't eat at all. Meanwhile spiders, ants, birds and even some bats are trying to eat them.

All lamprids have light organs in the egg, larval and pupal stage.  This is true of even the day-flying (diurinal) species discussed in the recent blog, which lose their bioluminescence in the adult stage when they would seem to need it most.  What purpose the light serves in the larvae is unknown, although some experts theorize that the light is an aposematic warning, telling predators "don't eat me, I taste bad and could make you sick."

This warning is not an empty threat.  Most firefly species have steroidal compounds that makes them distasteful or even toxic to predators, and the bioluminescence may be acting as a warning to potential predators.  These compounds are chemically related to the toxins on the skin of poisonous toads, called lucibufagins, a word that combines the Latin words for light and toad
Photuris eating another firefly
Photuris eating another firefly - Asknature.org- CC
Our larva above is in the genus Photuris, and one thing the adult females eat is known - other male fireflies.  These "femme fatale" fireflies have light flashing patterns designed to lure males of a different genus (Photinus), and it is not for sex.  These Photinus males have lucibufagins in their blood and when disturbed they can use "reflex bleeding" to release them as protection from jumping spiders and other predators.  Photuris females are aggressive predatory beetles and they are obtaining the blood of Photinus males, absorbing the toxic lucibufagins for their own defense.

It was early afternoon when I released my specimen on a dead log.  It crawled under the rotting bark looking for something to eat.  Thus ends my romantic story of fireflies.

Chris Barnhart had this to add:
"We should be seeing the adults soon. You can tell the Photuris males readily from their display - they have a greenish light and a faster pulse than the Photinus (remember Photuris as 'fast green'  and Photinus as 'slow yellow'."

Friday, May 22, 2015

Predator Guard from a Predator

Great crested flycatcher nest with snake skin -  the transient biologist
I have always been amazed how a tiny bird can build a complex nest on a small branch, balancing twigs, grass and even moss until it is firmly woven together.  Francis Skalicky's  article in the News-Leader added a material that was news to me - snake skins!
Tufted titmouse - Joe Motto
Both the Tufted Titmouse and the Blue Grosbeak commonly add bits of snake skin to their nest.  Other species including the Western Kingbird, Bewick's Wren and the House Wren may use snake skin, cellophane, or other flexible plastic as well.  These all would provide flexible, lightweight reinforcement to the twigs.

Research has shown that they may also serve as a predator deterrent as well, similar to a house sign warning that there is a burglar alarm inside. The Tufted Titmouse will incorporate bits of snake skin in its nest while a Great Crested Flycatcher may use a whole snake skin lining the nest with some hanging over the edges to show on the outside.  This flycatcher's eggs are frequently eaten by flying squirrels and rat snakes will take the eggs, the flycatcher and even the flying squirrel that is predating the nest.

So does the snake skin work as a deterrent?  A study described in Birds.com describes the proof.
"A test carried out by the researchers confirmed that to be so. Using 60 nest boxes in which quail eggs were placed, researchers added snake skins into 40 of the boxes, with 20 boxes having no snake skin in them. All of the 40 boxes with snake skins were left untouched, while up to 20 percent of the nests without snake skins were raided by flying squirrels – evidence that some birds use snake skins specifically to ward off predators, and it appears to work." 
If only a Black Rat Snake skin would deter the pack rats in our house!

Thursday, May 21, 2015

Bear in the Air

How far will a bear go for breakfast?  For this bear photographed in Canada and posted on Facebook, the sky was the limit.  It climbed up a power stanchion to reach a ravens' nest for a little scrambled eggs, paying no attention to the riled up parents.

Photographed during a wood bison hunt in Alberta by Linda Powell for Mossberg's website, the pictures immediately elicited cries of "Photoshop".  That ended with the publication of her video of the event.  You can watch it on Mossberg's outdoorhub website.

Thanks to MDC's black bear biologist Jeff Berringer for the lead.

Wednesday, May 20, 2015

Now Eat Your Carrion

When the chick is young the parents pick up small pieces of food and feed them to the chick, but as it gets older, it picks up these regurgitated food items on its own. Chicks remain in the nest for two to three months and continue to depend on their parents for a period of time after fledging, until they learn how to find and compete for food on their own. By the time they are ready to fledge, at three to six months old, the chicks are nearly the same size as their parents and are fully feathered, but their coloration is different. - See more at: http://animals.sandiegozoo.org/animals/vulture#sthash.tegIA6vt.dpuf
"Now eat your carrion like a good little vulture chick!"
I recently had the opportunity to watch our black vulture parent introduce the chicks to solid food.  Initially chicks are fed by the parent regurgitating digested food into their open mouths.  As they get older, the parent picks up small pieces of food and feeds them to the chick, before it learns how to pick up these regurgitated food items on its own.

I opened the stall door where the 5 day old chicks and parents are living.  The adults are accustomed to my visits and ignored me, while the chicks made a soft hiss when they felt threatened.  This time there were several strips of meat on the floor.  While I got my camera out I watched one chick repeatedly pick up a piece, trying to throw its head back to get it into its mouth.  It quit in frustration just as I was ready to film it.

"Tried it, didn't like it."
I have read that vultures will occasionally glean ticks.  This parent was gleaning a lot more than ticks.  Each time I opened the door to the stall, the parent stepped back and then started picking at things in the dirt, sometimes dropping an object, other times making a movement to swallow it.  Once I could see it was a small bug or beetle.  As you will see in this video, the parent is walking around the stall, gleaning insects from the stall floor, carefully selecting what to eat and what to discard.

These chicks will remain in the nest for two to three months, continuing to depend on their parents for regurgitated food until they fledge.  Even after taking flights across the field, they will depend on parental feeding for a while although they are nearly the size of the parents. *

Eat what?
A vulture's diet is enough to gag a maggot, so how do they survive eating carrion rotting in the sun for several days?  They can tolerate large loads of bacteria growing on carrion due to their unique mix of Clostridia and Fusobacteria gut bacteria.  Also, their gastric juice is far more acid than most birds, a remarkable pH of 1 to 2.

Like mothers everywhere, the adult eventually ate the piece of carrion to clean the plate.
In some countries in Southeast Asia, vultures are dying in large numbers.  The cattle that are revered are also treated with drugs like diclofenac.  When they die natural deaths rather than being butchered by humans  they are eaten by vultures which frequently develop kidney failure from the drugs.

*Sandiegozoo.org
There is a good overview of black and turkey vultures at Trekohio.com.
When the chick is young the parents pick up small pieces of food and feed them to the chick, but as it gets older, it picks up these regurgitated food items on its own. Chicks remain in the nest for two to three months and continue to depend on their parents for a period of time after fledging, until they learn how to find and compete for food on their own. By the time they are ready to fledge, at three to six months old, the chicks are nearly the same size as their parents and are fully feathered, but their coloration is different. - See more at: http://animals.sandiegozoo.org/animals/vulture#sthash.tegIA6vt.dpuf

Monday, May 18, 2015

No Bulb Firefly

Mating Fireflies
I saw a number of these insects on May 6th, crawling on the outside wall of our house as well as nearby trees.  While some spooked, this pair was committed to mating and made only one abortive attempt at flying.  When I transferred them to a photo board where the largest one measured a whopping 12mm, they tried to walk in separate directions without success.

They looked like fireflies but in May?  They are winter fireflies, Ellychnia corrusco, and their time of appearance is only part of their interesting story.  The photograph below was taken on April 12th in Maine by Mike Lewinsky.  He reported "I was shocked to see this beetle land on the snow in front of me, and doubly so when I realized it was a firefly. We are just beginning to see the first sign of insects returning for spring."
Winter Firefly Photo - Mike Lewinski Creative Commons
 A mark-recapture study done in Massachusetts in 2000 on the Life History and Mating Behavior of Ellychnia Corrusca showed that they overwintered as adults with low mortality. 
"By dissecting males and females sampled throughout late winter and spring, it was found that adults become reproductively active in early March, when male seminal vesicles first contained sperm and female ovaries first contained mature oocytes. Both sexes mated multiply during the approximately six-week mating season (early April through mid-May), and copulations lasted up to 28 h."
The genus Ellychnia is known as diurnal fireflies, meaning that they fly during the day.  Most notably they lack the "fire," that is they have no light producing organ as adults like their nocturnal cousins in the genus Photinus.  As overwintering adults which mate in March, it is likely too cold in evenings to fly so that they have evolved a different mechanism, attracting mates instead by pheromones.  

I wanted to photograph their lack of bioluminescent organs, but when I turned them over the loss of dignity was too much for them to stand and they parted ways and flew off in separate directions.  Maybe their timer said that the 28 hours were up.


Saturday, May 16, 2015

Yellow-Headed Blackbird




First let me enter a warning - I am not a "birder."  I say this not as a point of pride but in admiration for birders who study birds, identify their flight patterns and habits, recognize their calls (maybe), and keep track of where and when they see the first of a species or subsequent finds in nearby counties or distant lands.

Having said that, when I received an email from Charley Burwick titled "yellow-headed blackbird" which sounded like an oxymoron I thought he was blowing smoke.  Any school child has an image of a blackbird, featured in song as..... well a black bird.  But there was a picture that even he couldn't make up.

Ebird reported sightings- Darker =more frequent
In my defense, Charley tells me that any migration through Missouri is rare and brief and they are lucky to spot them. The yellow-headed blackbird winters in Mexico before migrating to the north-central states and Canada for breeding. They favor wetlands where they feed on insects and aquatic invertebrates. They often forage for seeds and grains in cultivated fields, mixing with flocks of other blackbird species. You can see on the EBird map of reported sightings above that their appearance in Missouri is very uncommon.

Displaying yellow-headed blackbird Courtesy of Ron Dudley
Like their red-winged blackbird cousins, they commonly cling to cattails while sending out their grinding, buzzing call.  Their displays can be incredible as described and illustrated by Ron Dudley at Featheredphotography.com.  The males aggressively defend their territory and may mate with up to 8 females, but generally will participate in raising only their first nesting.

Finally, if you ever are in a deep conversation with a birder, you can impress them with this fact.  "In 1825 Charles Lucien Bonaparte, nephew of Napoleon Bonaparte, gave the first detailed description of the yellow-headed blackbird, which was collected in 1820 by Thomas Say and Sir John Richardson."  Take that, Burwick!